Cylinder head gasket failure at offside after complete rebuild.
10 May 2015, 04:45 PM
#1
Cylinder head gasket failure at offside after complete rebuild.
Recently my engine main & big end bearings gave up the ghost. I whipped the engine out & sent it down South by pallet delivery to a highly recommended engineer for a complete rebuild.
On receiving the engine back I noted on start-up it was leaking coolant from the offside cylinder head, nearside was fine. I could see it dripping from the underside of the head down past the oil cooler modine. It was a drip every couple of minutes when it wasn’t running & the coolant was cold. On starting the car & heat up the leak turned into a constant drip. None of the cylinder heads were leaking prior to the engine overhaul. They were just skimmed as part of the recondition process being that the car had 131 k on the clock.
Both heads & blocks were skimmed & oversized gaskets installed to take up the meat removed by the machine shop, 1.5 mm or 1.6 mm oversized gasket if memory serves me correctly was fitted, anyway correct normal spec used after this type of work has been done. Also as part of the recon the internal combustion bores were drilled out to 20/1000th of an inch then cross hatched, new conrods, oversized pistons & rings, new ACL race bearings all round, refurb crankshaft, all cam & crank seals were done, valves adjusted & reseated, oil cooler modine changed, oil & water pumps changed, new timing belt, hydraulic tensioner & all guide & gear pullies changed, you get the idea a complete rebuild.
My experienced engine builder who does a lot of Subaru refurbs (he has 14 Subaru engines in his shop to rebuild now) recommended to me prior to receiving the engine that we go with an enlarged composite gasket rather than an enlarged multi-layer steel gasket on reassembly after the skimming process. Anyhow that what he used & we have a leak. I have had to take the engine back out & send it back down South to him for further investigation but he thinks that the only thing that could be wrong as he is sure everything is 100% with the trueness of the block & head skimming & the new gasket that was used is that one of the helicoils in the block that the head bolt screws into has given up after engine reassembly.
What he says can happen is after he has obtained the correct torque on the head stud using a torque wrench on rebuild I have then received & installed the engine & on start up the extra engine pressure & thermal expansion has caused one of the helicloils to detach from the block (could be slightly corroded) which would cause loss of torque on the head to the block & a leak.
Anyone have any other ideas what could be causing this apart from the obvious thinks like block or head uniformity after skimming is slightly out, wrong gasket. Has anyone been faced with a problem like this before? Any help/advice would be much appreciated as understandably the last thing I want is to get the engine back, install it & we still have a problem
. 
Thanks in advance.
On receiving the engine back I noted on start-up it was leaking coolant from the offside cylinder head, nearside was fine. I could see it dripping from the underside of the head down past the oil cooler modine. It was a drip every couple of minutes when it wasn’t running & the coolant was cold. On starting the car & heat up the leak turned into a constant drip. None of the cylinder heads were leaking prior to the engine overhaul. They were just skimmed as part of the recondition process being that the car had 131 k on the clock.
Both heads & blocks were skimmed & oversized gaskets installed to take up the meat removed by the machine shop, 1.5 mm or 1.6 mm oversized gasket if memory serves me correctly was fitted, anyway correct normal spec used after this type of work has been done. Also as part of the recon the internal combustion bores were drilled out to 20/1000th of an inch then cross hatched, new conrods, oversized pistons & rings, new ACL race bearings all round, refurb crankshaft, all cam & crank seals were done, valves adjusted & reseated, oil cooler modine changed, oil & water pumps changed, new timing belt, hydraulic tensioner & all guide & gear pullies changed, you get the idea a complete rebuild.
My experienced engine builder who does a lot of Subaru refurbs (he has 14 Subaru engines in his shop to rebuild now) recommended to me prior to receiving the engine that we go with an enlarged composite gasket rather than an enlarged multi-layer steel gasket on reassembly after the skimming process. Anyhow that what he used & we have a leak. I have had to take the engine back out & send it back down South to him for further investigation but he thinks that the only thing that could be wrong as he is sure everything is 100% with the trueness of the block & head skimming & the new gasket that was used is that one of the helicoils in the block that the head bolt screws into has given up after engine reassembly.
What he says can happen is after he has obtained the correct torque on the head stud using a torque wrench on rebuild I have then received & installed the engine & on start up the extra engine pressure & thermal expansion has caused one of the helicloils to detach from the block (could be slightly corroded) which would cause loss of torque on the head to the block & a leak.
Anyone have any other ideas what could be causing this apart from the obvious thinks like block or head uniformity after skimming is slightly out, wrong gasket. Has anyone been faced with a problem like this before? Any help/advice would be much appreciated as understandably the last thing I want is to get the engine back, install it & we still have a problem
. Thanks in advance.
10 May 2015, 05:39 PM
#3
Are you sure its not an external leak eg coolant crossover pipe 'O' rings, header tank/ pipework as its unusual to see a coolant leak from the head face joint or head gasket itself following a rebuild.
A version 5 engine uses a thin MLS gasket from the factory so just wondering why thick carbon composite gaskets have been used unless a lot of material has been removed from the head and deck faces or the new pistons have a different compression height.
Not knocking your engine builder, just intrigued about the gasket choice.
Mick
A version 5 engine uses a thin MLS gasket from the factory so just wondering why thick carbon composite gaskets have been used unless a lot of material has been removed from the head and deck faces or the new pistons have a different compression height.
Not knocking your engine builder, just intrigued about the gasket choice.
Mick
10 May 2015, 07:59 PM
#4
Hi Mick thanks for your reply. Prior to rebuilding engine the shell was dipped in acid batch & short motor painted gun metal grey & heads painted silver. Because of this it is really easy to see the pinkish nap free coolant against the back drop of the new paint. On the underside it is coming from between the block/deck & the head. On the top, front you can see the pinkish coolant pooling at the front of the engine just inside the intake manifold beside the same faces. The large diameter coolant hose located directly above that goes between the alloy coolant return pipe & the radiator isn’t leaking either, I have installed a jubilee clip on there rather the 2 wire type clips.
Prior to sending the engine I removed the pressure plate, friction plate, flywheel, exhaust headers & intake manifold. When I received the engine back I renewed the long under intake pipe (as it was pitted closer to the water pump side) that runs parallel with & bolts into the alloy coolant return line to the radiator & I also renewed the oil cooler modine pipe at the bottom, checked hoses & installed new 2 tab clips all round. Had a good examination when the engine was running of the potential leak areas around the offside head & found no leaks. Checked the following:
The aforementioned long pipe which connects to the nipple at the bottom of radiator filler tank via a short jumper hose.
The turbo bearing shell cooling coolant return line that goes into the back of radiator filler tank.
The main coolant silver alloy return line that goes into the radiator via large hose & clip. None were leaking.
Not sure what you mean by O rings, could you elaborate a bit more on that please?
In regards to the gaskets I thought it was standard practise after skimming both faces that you fit the thicker gasket which is either 1.5 or 1.6 mm (if memory serves me correctly). The reason I thought this is normal as the likes of ICP sell OEM MLS gaskets at this size for this very job. Mick are you saying that this is too much meat to remove & not the norm when skimming deck & head?
As for my builder choosing a composite gasket rather than MLS gasket he told me you are better with composite as it copes better with the thermal expansion than the steel gasket. He told me he has re-built loads & uses the composite successfully every time as I did question it when we were discussing the work. Please elaborate on why you think this is a poor choice. I just want to get to the bottom of it as I have spent a lot of money doing up my engine & am a bit worried. All I do know is it isn’t sealing on the offside but the nearside is sealing where he has used the same gasket obviously as they come as a set.
We also discussed compressions heights & he informed me we will end up with exactly the same heights as we are replacing the alloy meat with the same amount of composite meat. He then said you have to do this to keep everything the same as you would have problems with the internal engine pressure on boost if you didn’t.
Thanks again Mick.
Prior to sending the engine I removed the pressure plate, friction plate, flywheel, exhaust headers & intake manifold. When I received the engine back I renewed the long under intake pipe (as it was pitted closer to the water pump side) that runs parallel with & bolts into the alloy coolant return line to the radiator & I also renewed the oil cooler modine pipe at the bottom, checked hoses & installed new 2 tab clips all round. Had a good examination when the engine was running of the potential leak areas around the offside head & found no leaks. Checked the following:
The aforementioned long pipe which connects to the nipple at the bottom of radiator filler tank via a short jumper hose.
The turbo bearing shell cooling coolant return line that goes into the back of radiator filler tank.
The main coolant silver alloy return line that goes into the radiator via large hose & clip. None were leaking.
Not sure what you mean by O rings, could you elaborate a bit more on that please?
In regards to the gaskets I thought it was standard practise after skimming both faces that you fit the thicker gasket which is either 1.5 or 1.6 mm (if memory serves me correctly). The reason I thought this is normal as the likes of ICP sell OEM MLS gaskets at this size for this very job. Mick are you saying that this is too much meat to remove & not the norm when skimming deck & head?
As for my builder choosing a composite gasket rather than MLS gasket he told me you are better with composite as it copes better with the thermal expansion than the steel gasket. He told me he has re-built loads & uses the composite successfully every time as I did question it when we were discussing the work. Please elaborate on why you think this is a poor choice. I just want to get to the bottom of it as I have spent a lot of money doing up my engine & am a bit worried. All I do know is it isn’t sealing on the offside but the nearside is sealing where he has used the same gasket obviously as they come as a set.
We also discussed compressions heights & he informed me we will end up with exactly the same heights as we are replacing the alloy meat with the same amount of composite meat. He then said you have to do this to keep everything the same as you would have problems with the internal engine pressure on boost if you didn’t.
Thanks again Mick.
11 May 2015, 10:29 AM
#5
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This sounds wrong to me, he would of had to take 1.00mm off the heads/block to keep the same compression, thats alot! And why on earth would anyone use composite gaskets?
11 May 2015, 06:18 PM
#6
Thank for your reply wms.
I have just text my builder & asked him to confirm how much meat he took off? I don't know what the normal amount is to complete the skimming process. Do you happen to know as a rule of thumb what the normal combined amount is for skimming the block & head?
From your post on doing the math are you saying that the stock gap is about 0.5 millimetres with an untouched OEM MLS gasket in place?
The guy rebuilds engines for a living so I just went with his advice with regards to the composite gasket. What do you see as the big problem with using one? They must be useful in some situations or they wouldn't sell them. Or is it just purely down to cost for a cheaper alternative or are there some engineering situations where it is better to use composite over MLS?
Any information would be much appreciated. Thanks in advance.
I have just text my builder & asked him to confirm how much meat he took off? I don't know what the normal amount is to complete the skimming process. Do you happen to know as a rule of thumb what the normal combined amount is for skimming the block & head?
From your post on doing the math are you saying that the stock gap is about 0.5 millimetres with an untouched OEM MLS gasket in place?
The guy rebuilds engines for a living so I just went with his advice with regards to the composite gasket. What do you see as the big problem with using one? They must be useful in some situations or they wouldn't sell them. Or is it just purely down to cost for a cheaper alternative or are there some engineering situations where it is better to use composite over MLS?
Any information would be much appreciated. Thanks in advance.
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11 May 2015, 09:11 PM
#8
Ignore the green arrow in the picture showing a CDB cross hatching - the O rings I refer to are on the coolant cross over pipe ( top hose connects to it ) and can be seen below the head of the green arrow and on the opposite side of the block.
Carbon composite head gaskets would be fine on a Version 2 WRX ( to which they are fitted ) running 220 bhp from the factory but to run them on anything which is upgraded and tuned is questionable IMHO.
I always fit MLS gaskets whether they be OEM,Cosworth,RCM etc and never had a problem with failure.
As WMS said in his post, he must have removed a lot of material from the head/deck faces to warrant a +1.00mm thickness gasket assuming the new piston compression height and bowl are the same as standard.
Surface grind limit on the flame face of the cylinder head is 0.3mm ( 0.012")
The deck face of the block has a regrind limit of 0.1mm (0.004")
You can run into cam timing issues ( retarded ) with excessive amounts removed from the faces.
Mick
Last edited by merlin24; 11 May 2015 at 09:17 PM.
12 May 2015, 10:15 AM
#10
To do the job correctly it should have its head & block with piston measured correctly to determine what gasket thickness to fit,or any other machining operation to finalise piston heights / deck heights, composite gaskets are to be avoided & as stated fit MLS type.
12 May 2015, 06:30 PM
#11
Thanks guys for your information, all very much appreciated. I will be the first to admit that I am not that clued up myself on this but have did a bit of research into it which including speaking to many respected people in the know & also confirmed exactly what my engine builder has done. This is what I have been able to derive from what I’ve been told.
Guys my car is a 1994 cc Impreza turbo classic Uk version 5 with EJ205 engine running a standard 218 bhp standard from the factory. None of the heads were leaking at the time of rebuild. It was just part of the rebuild included in the costs to skim heads & blocks. As mentioned earlier there are other parameters that must be considered here being the engine was also bored out to 20/1000th or 0.5 mm, crosshatched & oversized pistons & rings fitted.
My engine builder removed a total of 0.2 mm of meat from the block & head combined so hope he didn’t take more than half of that off the deck to keep it within the limits you have kindly provided Mick. For some strange reason he thought that the OEM MLS gasket he removed from the car was 1.1 mm thick. Even stranger he then went & fitted a 1.6 mm composite gasket in it’s place when he rebuilt the engine? Don’t know how that works on the math (I will be speaking to him on the phone tonight) but the reason he gave me for using composite was it is more forgiving on sealing if there are slight discrepancies in the skimming process. Am I right in assuming the skimming process should be 100 % true, to say a 1/1000?
Here is what I found out today regarding the gasket sizes.
• All Subaru’s up to MY 98 had a 1. 6 mm cylinder head gasket fitted as stock.
• From MY99 onwards through the whole 2.0 litre range have 0.6 mm MLS head gaskets fitted as stock. So this is my car.
• The 2.5 litre engines have 0.8 mm gaskets fitted as stock. This means that no Subaru ever produced has a stock gasket size of 1.1 mm fitted as my engine builder seemed to think was the thickness of mine.
• Subaru UK cars had composite gaskets fitted on their cars up until MY98 then changed to MLS gaskets thereafter as they are a great improvement on composite. JDM cars changed to MLS gaskets in MY96 as they were having too much problems with leakage causing corrosion on internals.
All reputable people I have spoken to say (including you guys) why would you ever use them on an engine build as they are rubbish, best place for them is in the bin. Bad idea to even contemplate using composite gaskets on ej205 units even more so if increasing power later. The EJ205 came from the factory with MLS for a reason, the engine was designed to use this type of gasket by the people who build them, this UK version of the engine also seen the first HP increase to 218 bhp, hence MLS gasket installed as stock. I will be taking my classic up to 260 to 280 BHP if I can ever get to the bottom of my problems. I was planning to do this after the car was well run in.
Present situation with my car
• The combined amount removed during the skimming process was 0.2 mm. This means a 0.8 mm head gasket is required to be fitted to keep the distance to the cylinder head the same as the stock set up. My engine builder has installed a 1.6 mm gasket which in turn means the head is sitting 0.8 mm higher than the original set up, compression ratio. This works the other way now by giving us less compression (but what about the bored engine?) in the chamber than we had in the stock set up which doesn’t help our leaking gasket situation.
Another problem we need to think about is we have now raised the camshafts 0.8 mm higher than they should be (as Mick kindly has also mentioned) changing the working angle of the camshafts, the length of the belt, basically the timing of the engine has been adjusted slightly and we no longer have optimum performance set up. We need a 0.8 mm gasket to return everything to stock. Also we are presently leaking with a composite gasket in place so we really are in real trouble, the engine hasn’t even seen any boost yet & we have a leak. I have only done 20 miles prior to taking the engine back out. Think I need to ask my engine builder to re-check those heads & blocks closely.
Here is what a very knowledgeable Subaru person told me today. So is my engine builder smarter than I think & carried out a fluid test (as Motors S GT has kindly informed me of also) to work out the cubic capacity/volume of the engine at TDC (Remember my engine has been bored to 20/1000)?
Then from there work out what gasket size gives the correct compression ratio. This person told me Installing a gasket after changing all the parameters without working it out properly via a fluid test is like trying to win the lottery after only putting on 1 line. You have about as much chance of winning the lottery as getting the gasket size correct. I said but that will affect your timing as spoke about earlier. He said you can counter act this & started speaking about something like verneir pullies or something like that, I got a bit lost but got the feeling that it is better to maintain correct compression ratio & suffer a small amount out of time. I think you were also speaking about big money to for these pullies, not sure,like a say got a bit lost as am leaning all the time.
So what to do? I have no more money to lay out as spent a lot already. MY engine builder has received my engine back today & I will start on it tomorrow. I am thinking do I just get him to check blocks & heads, fit the 0.8 mm MLS gaskets taking all timing back to correct position but then thinking about fluid test to determine correct gasket size then timing being slightly out. Starting to go round in circles here & disappearing up my own rear end, chicken & egg scenario, oh what to do?
I am also really worried that we have a leak on the inside also past the fire ring on the gasket down into the combustion bore then we are in real trouble. Obviously I only did 22.8 miles after dropping the rebuilt engine back in & didn’t check to see if we had any sign of steam at the exhaust. Obviously diluting the oil’s lubricating properties with water isn’t good but with water not being compressible it could knacker up all my newly fitted ACL race bearings. Oh my head, Help!!!! Any help advice much appreciated.
Cheers Paul.https://www.scoobynet.com/images/smilies/cuckoo.gif
Guys my car is a 1994 cc Impreza turbo classic Uk version 5 with EJ205 engine running a standard 218 bhp standard from the factory. None of the heads were leaking at the time of rebuild. It was just part of the rebuild included in the costs to skim heads & blocks. As mentioned earlier there are other parameters that must be considered here being the engine was also bored out to 20/1000th or 0.5 mm, crosshatched & oversized pistons & rings fitted.
My engine builder removed a total of 0.2 mm of meat from the block & head combined so hope he didn’t take more than half of that off the deck to keep it within the limits you have kindly provided Mick. For some strange reason he thought that the OEM MLS gasket he removed from the car was 1.1 mm thick. Even stranger he then went & fitted a 1.6 mm composite gasket in it’s place when he rebuilt the engine? Don’t know how that works on the math (I will be speaking to him on the phone tonight) but the reason he gave me for using composite was it is more forgiving on sealing if there are slight discrepancies in the skimming process. Am I right in assuming the skimming process should be 100 % true, to say a 1/1000?
Here is what I found out today regarding the gasket sizes.
• All Subaru’s up to MY 98 had a 1. 6 mm cylinder head gasket fitted as stock.
• From MY99 onwards through the whole 2.0 litre range have 0.6 mm MLS head gaskets fitted as stock. So this is my car.
• The 2.5 litre engines have 0.8 mm gaskets fitted as stock. This means that no Subaru ever produced has a stock gasket size of 1.1 mm fitted as my engine builder seemed to think was the thickness of mine.
• Subaru UK cars had composite gaskets fitted on their cars up until MY98 then changed to MLS gaskets thereafter as they are a great improvement on composite. JDM cars changed to MLS gaskets in MY96 as they were having too much problems with leakage causing corrosion on internals.
All reputable people I have spoken to say (including you guys) why would you ever use them on an engine build as they are rubbish, best place for them is in the bin. Bad idea to even contemplate using composite gaskets on ej205 units even more so if increasing power later. The EJ205 came from the factory with MLS for a reason, the engine was designed to use this type of gasket by the people who build them, this UK version of the engine also seen the first HP increase to 218 bhp, hence MLS gasket installed as stock. I will be taking my classic up to 260 to 280 BHP if I can ever get to the bottom of my problems. I was planning to do this after the car was well run in.
Present situation with my car
• The combined amount removed during the skimming process was 0.2 mm. This means a 0.8 mm head gasket is required to be fitted to keep the distance to the cylinder head the same as the stock set up. My engine builder has installed a 1.6 mm gasket which in turn means the head is sitting 0.8 mm higher than the original set up, compression ratio. This works the other way now by giving us less compression (but what about the bored engine?) in the chamber than we had in the stock set up which doesn’t help our leaking gasket situation.
Another problem we need to think about is we have now raised the camshafts 0.8 mm higher than they should be (as Mick kindly has also mentioned) changing the working angle of the camshafts, the length of the belt, basically the timing of the engine has been adjusted slightly and we no longer have optimum performance set up. We need a 0.8 mm gasket to return everything to stock. Also we are presently leaking with a composite gasket in place so we really are in real trouble, the engine hasn’t even seen any boost yet & we have a leak. I have only done 20 miles prior to taking the engine back out. Think I need to ask my engine builder to re-check those heads & blocks closely.
Here is what a very knowledgeable Subaru person told me today. So is my engine builder smarter than I think & carried out a fluid test (as Motors S GT has kindly informed me of also) to work out the cubic capacity/volume of the engine at TDC (Remember my engine has been bored to 20/1000)?
Then from there work out what gasket size gives the correct compression ratio. This person told me Installing a gasket after changing all the parameters without working it out properly via a fluid test is like trying to win the lottery after only putting on 1 line. You have about as much chance of winning the lottery as getting the gasket size correct. I said but that will affect your timing as spoke about earlier. He said you can counter act this & started speaking about something like verneir pullies or something like that, I got a bit lost but got the feeling that it is better to maintain correct compression ratio & suffer a small amount out of time. I think you were also speaking about big money to for these pullies, not sure,like a say got a bit lost as am leaning all the time.
So what to do? I have no more money to lay out as spent a lot already. MY engine builder has received my engine back today & I will start on it tomorrow. I am thinking do I just get him to check blocks & heads, fit the 0.8 mm MLS gaskets taking all timing back to correct position but then thinking about fluid test to determine correct gasket size then timing being slightly out. Starting to go round in circles here & disappearing up my own rear end, chicken & egg scenario, oh what to do?
I am also really worried that we have a leak on the inside also past the fire ring on the gasket down into the combustion bore then we are in real trouble. Obviously I only did 22.8 miles after dropping the rebuilt engine back in & didn’t check to see if we had any sign of steam at the exhaust. Obviously diluting the oil’s lubricating properties with water isn’t good but with water not being compressible it could knacker up all my newly fitted ACL race bearings. Oh my head, Help!!!! Any help advice much appreciated.
Cheers Paul.https://www.scoobynet.com/images/smilies/cuckoo.gif
12 May 2015, 06:50 PM
#12
Thanks for the information Mick & the picture elaborating on the o rings. I see exactly what you mean now. There is a possibility it could have been coming from there, hard to see when intake manifold is in position. The engine will be stripped tomorrow so hopefully engine builder will pin point the problem & after speaking to him tonight I can sort out gasket situation.
Cheers Paul.
Cheers Paul.
Last edited by Paulgeorge01; 12 May 2015 at 06:51 PM. Reason: Wrote Cheers Paul twice.
12 May 2015, 07:06 PM
#13
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Phase 1 up to 1996 had 1.6mm fibre gaskets (dog bone shape pistons)
Phase 1.5 96/97 (V3/4) 1.2mm steel mls gaskets sqaure shaped combustion area in piston
Phase 2 98/99 on (V5) and all 2.0 engines after this 0.6mm mls gaskets
V5 onward have +2cc in the heads combustion area also, hence the thinner gasket.
Phase 1.5 96/97 (V3/4) 1.2mm steel mls gaskets sqaure shaped combustion area in piston
Phase 2 98/99 on (V5) and all 2.0 engines after this 0.6mm mls gaskets
V5 onward have +2cc in the heads combustion area also, hence the thinner gasket.
12 May 2015, 08:24 PM
#14
Hi WMS,
Thank you for that further clarification. You seem like a knowledgeable chap. What do you think in regards to going with a 0.8 mm gasket in turn moving cam & timing back to original (ignoring fluid check) or
Carrying out fluid check & computation with the larger pistons being installed that could result in a gasket for argument sake of 1.6 mm being fitted (if my engine builder is correct) to keep correct compression ratio in turn ignoring the timing is slightly out by 0.8 mm?
What would you do?
Cheers Paul.
Thank you for that further clarification. You seem like a knowledgeable chap. What do you think in regards to going with a 0.8 mm gasket in turn moving cam & timing back to original (ignoring fluid check) or
Carrying out fluid check & computation with the larger pistons being installed that could result in a gasket for argument sake of 1.6 mm being fitted (if my engine builder is correct) to keep correct compression ratio in turn ignoring the timing is slightly out by 0.8 mm?
What would you do?
Cheers Paul.
12 May 2015, 08:52 PM
#15
Hopefully your engine builder will remove both cylinder heads and throw the composite head gaskets in the nearest bin, volume the combustion chambers on the heads and add that result along with the measured piston deck height etc to his C.R calculation in order to select the correct thickness gasket.
Would imagine your C.R at the moment with the 1.6mm composite gaskets would be around 7.5:1 which is quite low.
RCM do their own range of stopper MLS head gaskets in various thickness including a 0.78mm gasket which might be of use.
Mick
Would imagine your C.R at the moment with the 1.6mm composite gaskets would be around 7.5:1 which is quite low.
RCM do their own range of stopper MLS head gaskets in various thickness including a 0.78mm gasket which might be of use.
Mick
12 May 2015, 09:07 PM
#16
Thanks Mick.
If it did turn out to be 0.78 mm then that also kills the 2 birds with 1 stone putting the cams back to original position, not exactly but within 0.02 mm so all would be well with timing too.
Just out of curiosity & for the purpose of learning if it happened to calculate for argument sake to be higher like 1.6 mm what would you do go for? The correct height on the cams to keep timing spot on (0.8 mm) or go with the calculation for arguments sake being 1. 6 mm & sacrifice timing being adjusted out slightly by 0.8 mm?
I am guessing RCM is an abbreviation for a supplier, what is the name of the supplier?
Cheers Paul.
If it did turn out to be 0.78 mm then that also kills the 2 birds with 1 stone putting the cams back to original position, not exactly but within 0.02 mm so all would be well with timing too.
Just out of curiosity & for the purpose of learning if it happened to calculate for argument sake to be higher like 1.6 mm what would you do go for? The correct height on the cams to keep timing spot on (0.8 mm) or go with the calculation for arguments sake being 1. 6 mm & sacrifice timing being adjusted out slightly by 0.8 mm?
I am guessing RCM is an abbreviation for a supplier, what is the name of the supplier?
Cheers Paul.
12 May 2015, 09:13 PM
#17
Sounds to me like you need to get your engine to someone that knows what they are talking about, I don't know much about WMS but he seems to know his onions, the other is Mick from API and Motors GT is Paul Finch both of whom are very well respected, but to be fair by the sounds of it you'd be doing a lot better if you used anyone of the three.
13 May 2015, 04:12 PM
#19
Thanks Mick.
You are right ditchmyster but didn't know about these guys as haven't been on the forum much. Didn't have time to do most of my own work due to working away but this has changed so getting right into it now & doing all the easier DIY stuff myself so am using the forum a bit more. I have driven my V5 classic for 15 years & it still puts a big smile on my face. Am also enjoying increasing my knowledge especially with the sterling advice from all the guys, just look at the knowledge base on this thread alone. Thank you very much to all of you for the advice received to date.
Spoke to engine builder yesterday after he had removed the offside head & it went something like this.
Reason for the leak: One out of the six internal threads in the block was damaged. It was a bottom one in the vicinity of where I could see the bottom leak. On removal 5 out of the 6 head bolts required the normal amount of torque to break over & the culprit (#6) was quite loose. He assures me that all 6 took the torque on the torque wrench when the engine was reassembled. He thinks on start up with extra internal pressure of the engine running is what caused the thread to fail. He was taking the block to the machine shop today to get it sorted out. He told me he ran a tap down the other 5 & they were all perfect.
Can you helicoil these?
I also had coolant leaking at the top of the deck head face as well as the bottom. Could this not mean the top block thread could be suspect too?
Told him about all the advice I had received pertaining to gasket thickness & type, volumetric capacity/fluid checks/calculations to determine CR. This was his train of thought.
He knew that the OEM gasket in my car was supposed to be 0.6 mm but what he said was on strip down he said it was more like 1.1 mm MLS. I said it can't be as the engine has never been apart from the factory as I have owned the car since it was 6 months old. I asked how can you tell that it was closer to 1.1 than 0.6 after it has been removed from the face under no torque & the multilayers are loose? He answered experience. He also said that through his experience that not all Subaru engines that come from the factory have the specified gasket width in place, there are differences when they are originally machined. If it is out of speck after checking at the factory as part of quality control they just fit a larger gasket. Sounds a bit dubious to me as I'm guess this type of work would be done by computerised CNC machines or something like that.
What you think of the 1.1 mm explanation for a starting point/datum for his calculations?
Then the explanation of the reason why he finished at a 1.6 mm gasket was as follows: 0.2 mm of meat removed (less than 0.1 from deck). Taking it to 1.3 mm then to compensate for the boring of the engine to 0.5 mm (20/1000") & installing new oversized pistons & rings to match & to stop over pressuring the engine on boost. He increased the head length by a further 0.3 mm. I asked how did you arrive at that did you carry out the fluid calculation & measurements as previously discussed? He told he knew through experience building 100's of Subaru engines with these oversized pistons that this was what was required to reduce the pressure so as not to give/cause problems to my engine with too high an internal pressure on boost.
What you think of that? After the benefit of the hearing from an expert knowledge base in this thread I don't like the sound of it, He is making assumptions rather than doing the measuring & calculating.
I asked about what affect would the increase in cam height have in regards to timing? 0.5 mm if his 1.1 MLS gasket theory is correct or 0.8 mm increase if it was indeed a 0.6 mm MLS gasket that was fitted originally.
He said it will be fine. What you make of that then?
Cheers
Paul.
You are right ditchmyster but didn't know about these guys as haven't been on the forum much. Didn't have time to do most of my own work due to working away but this has changed so getting right into it now & doing all the easier DIY stuff myself so am using the forum a bit more. I have driven my V5 classic for 15 years & it still puts a big smile on my face. Am also enjoying increasing my knowledge especially with the sterling advice from all the guys, just look at the knowledge base on this thread alone. Thank you very much to all of you for the advice received to date.
Spoke to engine builder yesterday after he had removed the offside head & it went something like this.
Reason for the leak: One out of the six internal threads in the block was damaged. It was a bottom one in the vicinity of where I could see the bottom leak. On removal 5 out of the 6 head bolts required the normal amount of torque to break over & the culprit (#6) was quite loose. He assures me that all 6 took the torque on the torque wrench when the engine was reassembled. He thinks on start up with extra internal pressure of the engine running is what caused the thread to fail. He was taking the block to the machine shop today to get it sorted out. He told me he ran a tap down the other 5 & they were all perfect.
Can you helicoil these?
I also had coolant leaking at the top of the deck head face as well as the bottom. Could this not mean the top block thread could be suspect too?
Told him about all the advice I had received pertaining to gasket thickness & type, volumetric capacity/fluid checks/calculations to determine CR. This was his train of thought.
He knew that the OEM gasket in my car was supposed to be 0.6 mm but what he said was on strip down he said it was more like 1.1 mm MLS. I said it can't be as the engine has never been apart from the factory as I have owned the car since it was 6 months old. I asked how can you tell that it was closer to 1.1 than 0.6 after it has been removed from the face under no torque & the multilayers are loose? He answered experience. He also said that through his experience that not all Subaru engines that come from the factory have the specified gasket width in place, there are differences when they are originally machined. If it is out of speck after checking at the factory as part of quality control they just fit a larger gasket. Sounds a bit dubious to me as I'm guess this type of work would be done by computerised CNC machines or something like that.
What you think of the 1.1 mm explanation for a starting point/datum for his calculations?
Then the explanation of the reason why he finished at a 1.6 mm gasket was as follows: 0.2 mm of meat removed (less than 0.1 from deck). Taking it to 1.3 mm then to compensate for the boring of the engine to 0.5 mm (20/1000") & installing new oversized pistons & rings to match & to stop over pressuring the engine on boost. He increased the head length by a further 0.3 mm. I asked how did you arrive at that did you carry out the fluid calculation & measurements as previously discussed? He told he knew through experience building 100's of Subaru engines with these oversized pistons that this was what was required to reduce the pressure so as not to give/cause problems to my engine with too high an internal pressure on boost.
What you think of that? After the benefit of the hearing from an expert knowledge base in this thread I don't like the sound of it, He is making assumptions rather than doing the measuring & calculating.
I asked about what affect would the increase in cam height have in regards to timing? 0.5 mm if his 1.1 MLS gasket theory is correct or 0.8 mm increase if it was indeed a 0.6 mm MLS gasket that was fitted originally.
He said it will be fine. What you make of that then?
Cheers
Paul.
14 May 2015, 08:49 PM
#20
You are right ditchmyster but didn't know about these guys as haven't been on the forum much. Didn't have time to do most of my own work due to working away but this has changed so getting right into it now & doing all the easier DIY stuff myself so am using the forum a bit more. I have driven my V5 classic for 15 years & it still puts a big smile on my face. Am also enjoying increasing my knowledge especially with the sterling advice from all the guys, just look at the knowledge base on this thread alone. Thank you very much to all of you for the advice received to date.
Spoke to engine builder yesterday after he had removed the offside head & it went something like this.
Reason for the leak: One out of the six internal threads in the block was damaged. It was a bottom one in the vicinity of where I could see the bottom leak. On removal 5 out of the 6 head bolts required the normal amount of torque to break over & the culprit (#6) was quite loose. He assures me that all 6 took the torque on the torque wrench when the engine was reassembled. He thinks on start up with extra internal pressure of the engine running is what caused the thread to fail. He was taking the block to the machine shop today to get it sorted out. He told me he ran a tap down the other 5 & they were all perfect.
Can you helicoil these?
I also had coolant leaking at the top of the deck head face as well as the bottom. Could this not mean the top block thread could be suspect too?
Told him about all the advice I had received pertaining to gasket thickness & type, volumetric capacity/fluid checks/calculations to determine CR. This was his train of thought.
He knew that the OEM gasket in my car was supposed to be 0.6 mm but what he said was on strip down he said it was more like 1.1 mm MLS. I said it can't be as the engine has never been apart from the factory as I have owned the car since it was 6 months old. I asked how can you tell that it was closer to 1.1 than 0.6 after it has been removed from the face under no torque & the multilayers are loose? He answered experience. He also said that through his experience that not all Subaru engines that come from the factory have the specified gasket width in place, there are differences when they are originally machined. If it is out of speck after checking at the factory as part of quality control they just fit a larger gasket. Sounds a bit dubious to me as I'm guess this type of work would be done by computerised CNC machines or something like that.
What you think of the 1.1 mm explanation for a starting point/datum for his calculations?
Then the explanation of the reason why he finished at a 1.6 mm gasket was as follows: 0.2 mm of meat removed (less than 0.1 from deck). Taking it to 1.3 mm then to compensate for the boring of the engine to 0.5 mm (20/1000") & installing new oversized pistons & rings to match & to stop over pressuring the engine on boost. He increased the head length by a further 0.3 mm. I asked how did you arrive at that did you carry out the fluid calculation & measurements as previously discussed? He told he knew through experience building 100's of Subaru engines with these oversized pistons that this was what was required to reduce the pressure so as not to give/cause problems to my engine with too high an internal pressure on boost.
What you think of that? After the benefit of the hearing from an expert knowledge base in this thread I don't like the sound of it, He is making assumptions rather than doing the measuring & calculating.
I asked about what affect would the increase in cam height have in regards to timing? 0.5 mm if his 1.1 MLS gasket theory is correct or 0.8 mm increase if it was indeed a 0.6 mm MLS gasket that was fitted originally.
He said it will be fine. What you make of that then?
Cheers
Paul.[/QUOTE]
That is the biggest crock of sh*t I have heard in a long time but did make me chuckle
Not once have I seen an engine from the factory with 'other sized' gaskets due to manufacturing tolerances in the 10 years I have been building Subaru engines.
At the end of the day, your engine builder needs to measure everything and calculate the correct gasket thickness from his measurements - something we can not do via the 'net without measuring it hands on.
As for the block thread/bolt which has failed 'post torque-angle tightening and post heat cycle', did your engine builder use new head bolts in the build ?
Subaru use a torque-angle method for the head bolt tightening sequence which pre-loads them into the plastic region and when the engine is heat cycled for the first time, the bolts stretch even further due to the different thermal expansion rates of the aluminium head/block and steel bolt giving a good clamping force and negating the need to re-torque the heads again as we used to do years ago.
The torque-angle method leaves the old bolts permanently stretched. Old bolts can bottom out in the blind thread hole and not achieve the correct torque-angle or even break due to the previous stretch.
Hope you manage to get your issues resolved.
Mick
Spoke to engine builder yesterday after he had removed the offside head & it went something like this.
Reason for the leak: One out of the six internal threads in the block was damaged. It was a bottom one in the vicinity of where I could see the bottom leak. On removal 5 out of the 6 head bolts required the normal amount of torque to break over & the culprit (#6) was quite loose. He assures me that all 6 took the torque on the torque wrench when the engine was reassembled. He thinks on start up with extra internal pressure of the engine running is what caused the thread to fail. He was taking the block to the machine shop today to get it sorted out. He told me he ran a tap down the other 5 & they were all perfect.
Can you helicoil these?
I also had coolant leaking at the top of the deck head face as well as the bottom. Could this not mean the top block thread could be suspect too?
Told him about all the advice I had received pertaining to gasket thickness & type, volumetric capacity/fluid checks/calculations to determine CR. This was his train of thought.
He knew that the OEM gasket in my car was supposed to be 0.6 mm but what he said was on strip down he said it was more like 1.1 mm MLS. I said it can't be as the engine has never been apart from the factory as I have owned the car since it was 6 months old. I asked how can you tell that it was closer to 1.1 than 0.6 after it has been removed from the face under no torque & the multilayers are loose? He answered experience. He also said that through his experience that not all Subaru engines that come from the factory have the specified gasket width in place, there are differences when they are originally machined. If it is out of speck after checking at the factory as part of quality control they just fit a larger gasket. Sounds a bit dubious to me as I'm guess this type of work would be done by computerised CNC machines or something like that.
What you think of the 1.1 mm explanation for a starting point/datum for his calculations?
Then the explanation of the reason why he finished at a 1.6 mm gasket was as follows: 0.2 mm of meat removed (less than 0.1 from deck). Taking it to 1.3 mm then to compensate for the boring of the engine to 0.5 mm (20/1000") & installing new oversized pistons & rings to match & to stop over pressuring the engine on boost. He increased the head length by a further 0.3 mm. I asked how did you arrive at that did you carry out the fluid calculation & measurements as previously discussed? He told he knew through experience building 100's of Subaru engines with these oversized pistons that this was what was required to reduce the pressure so as not to give/cause problems to my engine with too high an internal pressure on boost.
What you think of that? After the benefit of the hearing from an expert knowledge base in this thread I don't like the sound of it, He is making assumptions rather than doing the measuring & calculating.
I asked about what affect would the increase in cam height have in regards to timing? 0.5 mm if his 1.1 MLS gasket theory is correct or 0.8 mm increase if it was indeed a 0.6 mm MLS gasket that was fitted originally.
He said it will be fine. What you make of that then?
Cheers
Paul.[/QUOTE]
That is the biggest crock of sh*t I have heard in a long time but did make me chuckle
Not once have I seen an engine from the factory with 'other sized' gaskets due to manufacturing tolerances in the 10 years I have been building Subaru engines.At the end of the day, your engine builder needs to measure everything and calculate the correct gasket thickness from his measurements - something we can not do via the 'net without measuring it hands on.
As for the block thread/bolt which has failed 'post torque-angle tightening and post heat cycle', did your engine builder use new head bolts in the build ?
Subaru use a torque-angle method for the head bolt tightening sequence which pre-loads them into the plastic region and when the engine is heat cycled for the first time, the bolts stretch even further due to the different thermal expansion rates of the aluminium head/block and steel bolt giving a good clamping force and negating the need to re-torque the heads again as we used to do years ago.
The torque-angle method leaves the old bolts permanently stretched. Old bolts can bottom out in the blind thread hole and not achieve the correct torque-angle or even break due to the previous stretch.
Hope you manage to get your issues resolved.
Mick
15 May 2015, 12:03 AM
#21
Again Mick you have taken the time out of your day to help me & to give me the truth about this situation & for that I am truly grateful.
I am more than sure in the short time I have been corresponding with you in this thread that you know your stuff & you are a true professional/expert Subaru engine builder. I am a very keen DIY mechanic/Subaru enthusiast but have a lot to learn. Even with my very limited knowledge on the subject from doing a bit of research & listening to what yourself & the other engine builders have kindly added to assist, I am even smelling something & lets just say it isn't roses :-(.
I have also noticed that my buider is desperate to get off the phone now when I call due to me hitting him with all the tech data you guys have kindly provided. I am really stressed out with it all as have spent a lot of money on the build which I don't want to see go to waste. I now know where I will be coming to get my engines done in the future. I am planning a few more projects in the future & I now know where I won't be going.
I don't know if he used new head bolts in the build but I understand fully from an engineering prospective & from your explanation as why it is a must. That explains why it failed after start up. It was the offside - top - front thread that failed in the block. Hence the leak there & in the vicinity of the oil cooler modine as it was running from the top down the back of the timing belt cover to this area.
I will ask the question. He is going to take off the other head & replace both gaskets with MLS. He said he will do his calculation method but is still speaking about the thicker gaskets, using what he says was the original 1.2 mm gasket rather than the 0.6 mm we both know is correct from the factory, nightmare?
I have paid for the engine build in full before the engine was sent back to me the first time. On the back of the information you have kindly provided it is imperative now that we get a full set of new head bolts to do both sides which I will pay for myself if he says it's not required but hopefully he will know & be using new bolts. If required I will also cut & paste your explanation & send via email so he has an expert explanation of why this is obviously a must. A stainless steel helicoil has been installed to substitute the failed thread in the block.
Mick I fully understand what you have said in regards to why you obviously need to get your hands on an engine to obtain all the measurements & information to complete the calculations to obtain the exact gasket thickness.
Just as a rule of thumb & for the process of trying to learn a bit more. My car had a 0.6 mm head gasket originally, he took 0.2 mm off during the skimming process taking us to 0.8 mm. The engine was bored to 0.5 mm & new rods, oversized rings & pistons were installed to match.
From an engineering prospective cross sectional area x pressure = force. If the crank stroke length has not changed, exact same length rods & pistons as the stock ones they replaced, I am guess that why you need to measure to deck face or carry out a fluid test to work out the volumetric capacity at TDC as part of the calculation. But if they are the same length then from an engineering prospective then there will be an extra internal engine force in each bore equivalent to the increase in cross sectional area (0.5 mm) x pressure. The only way to alleviate that extra pressure/force would be to increase the area (length of the combustion chamber) of where the pressure/force is being exerted on which would be done by installing a thicker gasket. That's how I am understanding it from a layman's prospective or I'm I completely barking up the wrong tree here which is more than possible :-).
I don't know the formula to work this out but I do understand engineering & pressure, volume, area calculations as I used to drill oil wells for a living. But if I am right in this situation using the aforementioned mechanical parameters then the head gasket thickness would need to increase above 0.8 mm to maintain CR continuity?
Sorry for all the questions, just wan't to increase my knowledge & understand. Living up in the north east of Scotland it is not often I get the chance to speak to a person of your knowledge/calibre.
Cheers Paul.
I am more than sure in the short time I have been corresponding with you in this thread that you know your stuff & you are a true professional/expert Subaru engine builder. I am a very keen DIY mechanic/Subaru enthusiast but have a lot to learn. Even with my very limited knowledge on the subject from doing a bit of research & listening to what yourself & the other engine builders have kindly added to assist, I am even smelling something & lets just say it isn't roses :-(.
I have also noticed that my buider is desperate to get off the phone now when I call due to me hitting him with all the tech data you guys have kindly provided. I am really stressed out with it all as have spent a lot of money on the build which I don't want to see go to waste. I now know where I will be coming to get my engines done in the future. I am planning a few more projects in the future & I now know where I won't be going.
I don't know if he used new head bolts in the build but I understand fully from an engineering prospective & from your explanation as why it is a must. That explains why it failed after start up. It was the offside - top - front thread that failed in the block. Hence the leak there & in the vicinity of the oil cooler modine as it was running from the top down the back of the timing belt cover to this area.
I will ask the question. He is going to take off the other head & replace both gaskets with MLS. He said he will do his calculation method but is still speaking about the thicker gaskets, using what he says was the original 1.2 mm gasket rather than the 0.6 mm we both know is correct from the factory, nightmare?
I have paid for the engine build in full before the engine was sent back to me the first time. On the back of the information you have kindly provided it is imperative now that we get a full set of new head bolts to do both sides which I will pay for myself if he says it's not required but hopefully he will know & be using new bolts. If required I will also cut & paste your explanation & send via email so he has an expert explanation of why this is obviously a must. A stainless steel helicoil has been installed to substitute the failed thread in the block.
Mick I fully understand what you have said in regards to why you obviously need to get your hands on an engine to obtain all the measurements & information to complete the calculations to obtain the exact gasket thickness.
Just as a rule of thumb & for the process of trying to learn a bit more. My car had a 0.6 mm head gasket originally, he took 0.2 mm off during the skimming process taking us to 0.8 mm. The engine was bored to 0.5 mm & new rods, oversized rings & pistons were installed to match.
From an engineering prospective cross sectional area x pressure = force. If the crank stroke length has not changed, exact same length rods & pistons as the stock ones they replaced, I am guess that why you need to measure to deck face or carry out a fluid test to work out the volumetric capacity at TDC as part of the calculation. But if they are the same length then from an engineering prospective then there will be an extra internal engine force in each bore equivalent to the increase in cross sectional area (0.5 mm) x pressure. The only way to alleviate that extra pressure/force would be to increase the area (length of the combustion chamber) of where the pressure/force is being exerted on which would be done by installing a thicker gasket. That's how I am understanding it from a layman's prospective or I'm I completely barking up the wrong tree here which is more than possible :-).
I don't know the formula to work this out but I do understand engineering & pressure, volume, area calculations as I used to drill oil wells for a living. But if I am right in this situation using the aforementioned mechanical parameters then the head gasket thickness would need to increase above 0.8 mm to maintain CR continuity?
Sorry for all the questions, just wan't to increase my knowledge & understand. Living up in the north east of Scotland it is not often I get the chance to speak to a person of your knowledge/calibre.
Cheers Paul.
15 May 2015, 12:47 AM
#22
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This won't be what you want to hear... But anyway... For me I would cut my losses right here and now.. Yes you've sunk monies into this builder... But your not getting anywhere with it and it's only going to run and run with the current builder... You've already said he is cutting short your phone calls..??
You say your a keen diyer...? Would you be confident enough of removing your engine and replacing it?? If so then I would seriously think about removing it and sending it to one of the well known engine builders on here.. Get them to do the work then you put the engine back.. Either that or your going to go on a long road trip with a return journey by train... Have a look at AS performance... Not sure if they do the work you require.. I'm pretty sure they do..! And they are in Newcastle I think...! I hope I got that right.! The point being.. I think it's time to go elsewhere.
Good luck.
You say your a keen diyer...? Would you be confident enough of removing your engine and replacing it?? If so then I would seriously think about removing it and sending it to one of the well known engine builders on here.. Get them to do the work then you put the engine back.. Either that or your going to go on a long road trip with a return journey by train... Have a look at AS performance... Not sure if they do the work you require.. I'm pretty sure they do..! And they are in Newcastle I think...! I hope I got that right.! The point being.. I think it's time to go elsewhere.
Good luck.
20 May 2015, 12:21 AM
#23
To answer your question Mick my engine builder didn't use new cylinder head bolts. I purchased a set & sent them directly to his garage.
The corrective work on my engine has now been completed & it was picked up this afternoon by national pallets. I hope to get it back Friday or Tuesday of next week because of holiday Monday. I will install the engine & have it up & running on the day I receive it, so fingers crossed as this will be the 3rd time I have had this engine out & in recently. Could be 3rd time lucky.
I now have MLS gaskets rather than composite & brand new cylinder head bolts.
The engine builder said he carried out his calculations & has installed 1.3 mm MLS gaskets. Original was 0.6 mm, skimmed was 0.2 mm so this is a 0.5 mm extension to compensate for the engine being bored to 20/1000 (0.5 mm) & the new oversized pistons & rings to match being installed.
Couldn't really take it any further with questioning his gasket thickness choice as don't know the exact detail on how to do the calculation.
Kindly provided by Mick. Volume the combustion chambers on the heads and add that result along with the measured piston deck height etc to his C.R calculation in order to select the correct thickness gasket.
Can anyone add to this for example with a step by step guide including the units you use for volume & measurements. Do you take the measurement in litres when engine is at TDC? Do you take the height & add it in millimetres? How do you do the calculation itself? As with all calculations I am guessing you have to multiply or divide by a constant at some point in the calculation to covert the answer back to a gasket thickness in millimetres? I would like to know how to do this as it would be handy to know for the future.
A BIG thanks to all the people who gave advice. Much appreciated.
Cheers Paul.
The corrective work on my engine has now been completed & it was picked up this afternoon by national pallets. I hope to get it back Friday or Tuesday of next week because of holiday Monday. I will install the engine & have it up & running on the day I receive it, so fingers crossed as this will be the 3rd time I have had this engine out & in recently. Could be 3rd time lucky.
I now have MLS gaskets rather than composite & brand new cylinder head bolts.
The engine builder said he carried out his calculations & has installed 1.3 mm MLS gaskets. Original was 0.6 mm, skimmed was 0.2 mm so this is a 0.5 mm extension to compensate for the engine being bored to 20/1000 (0.5 mm) & the new oversized pistons & rings to match being installed.
Couldn't really take it any further with questioning his gasket thickness choice as don't know the exact detail on how to do the calculation.
Kindly provided by Mick. Volume the combustion chambers on the heads and add that result along with the measured piston deck height etc to his C.R calculation in order to select the correct thickness gasket.
Can anyone add to this for example with a step by step guide including the units you use for volume & measurements. Do you take the measurement in litres when engine is at TDC? Do you take the height & add it in millimetres? How do you do the calculation itself? As with all calculations I am guessing you have to multiply or divide by a constant at some point in the calculation to covert the answer back to a gasket thickness in millimetres? I would like to know how to do this as it would be handy to know for the future.
A BIG thanks to all the people who gave advice. Much appreciated.
Cheers Paul.
20 May 2015, 09:55 AM
#24
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To start with, the overbore in piston size will make virtually no differnece to CR, its not a large enough gain in engine capacity to matter, a gain of 0.5mm bore size will increase CR by 0.08, so no need to adjust the gasket thickness at all for that. Increasing the gasket thickness by 0.5mm drops the CR by approx 0.4 ie std gasket 0.6 = 8.5:1 new gasket 1.1 = 8.1:1 cr.
there are plebty of CR tools on the web, they are only any use if you have the tools and knowledge to be able to do it right of course. It sounds like you are in a better place now than when you started, good luck and I hope it's ok now. Sorry I havn't been more involved with this thread but I'm far too busy building engines :-)
Andy Williams
there are plebty of CR tools on the web, they are only any use if you have the tools and knowledge to be able to do it right of course. It sounds like you are in a better place now than when you started, good luck and I hope it's ok now. Sorry I havn't been more involved with this thread but I'm far too busy building engines :-)
Andy Williams
20 May 2015, 01:47 PM
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Don't forget that there is 2 CR's, static and dynamic, static is just the mechanical difference between swept and compressed volumes, dynamic is when the engine is running and cam profile and timing then comes into it, ie you can gain/loose CR with the overlap of the cams opening and closing. Thats not really relevant for this thread though.
21 May 2015, 11:54 PM
#27
Thanks WMS for the info. I can see why you are so busy building engines.
Thanks FMJ for the link. Good to see how it's done.
WMS you obviously know your stuff. With my CR being reduced approximately as per your second last post. Increasing the gasket thickness by 0.5mm drops the CR by approx 0.4 ie std gasket 0.6 = 8.5:1 new gasket 1.1 = 8.1:1 cr.
Am I correct in assuming that this will most definitely reduce engine efficiency? My BHP will be reduced & my fuel consumption will go up slightly? I have no choice but to live with this for the time being.
Obviously this isn't where I would like to be. Will this situation cause my engine to wear prematurely? I'm am hoping that 0.5 mm higher cam height (timing) & reduced CR isn't going to be that detrimental to the longevity of my engine having just shelled out a heap of ££ for it to be reconditioned.
Thanks to the information provided on the forum I'm definitely in a better situation than I was before. More importantly I have also made contact with some proper engine builders. I will be giving my builder a call once I have received the engine & got it running. I will ask for an explanation oh his CR calc's/gasket choice of 1.3 mm. TBC.
Cheers Paul.
Thanks FMJ for the link. Good to see how it's done.
WMS you obviously know your stuff. With my CR being reduced approximately as per your second last post. Increasing the gasket thickness by 0.5mm drops the CR by approx 0.4 ie std gasket 0.6 = 8.5:1 new gasket 1.1 = 8.1:1 cr.
Am I correct in assuming that this will most definitely reduce engine efficiency? My BHP will be reduced & my fuel consumption will go up slightly? I have no choice but to live with this for the time being.
Obviously this isn't where I would like to be. Will this situation cause my engine to wear prematurely? I'm am hoping that 0.5 mm higher cam height (timing) & reduced CR isn't going to be that detrimental to the longevity of my engine having just shelled out a heap of ££ for it to be reconditioned.
Thanks to the information provided on the forum I'm definitely in a better situation than I was before. More importantly I have also made contact with some proper engine builders. I will be giving my builder a call once I have received the engine & got it running. I will ask for an explanation oh his CR calc's/gasket choice of 1.3 mm. TBC.
Cheers Paul.
