Not Again! H/G Failure on Forged 2.5 Build
03 March 2017, 01:00 PM
#31
Scooby Regular
Can't comment on the torque condition of mine as the work was done about 15 months ago by a shop.
As for RCM bolts, from my understanding they used to sell one spec of high tensile head stud, but now they sell 2 specs, 'high tensile' and 'extreme', rated 350hp and 450hp respectively. That makes me wonder if they had a problem with old single spec range (i.e. it was sold as rated as higher than it could cope with), so down graded it and brought in the extreme ones also.......
As for RCM bolts, from my understanding they used to sell one spec of high tensile head stud, but now they sell 2 specs, 'high tensile' and 'extreme', rated 350hp and 450hp respectively. That makes me wonder if they had a problem with old single spec range (i.e. it was sold as rated as higher than it could cope with), so down graded it and brought in the extreme ones also.......
03 March 2017, 01:28 PM
#33
For info
I have run my sprint car to over 550/550 on 11mm RCM extreme. When torqued to 90ftlbs no issues
My drag car has used 11mm cosworth bolts for years, just come apart again no gasket issues. Ran up to 2.7 bar!
Not saying 14mm isn't ever needed just that there are a lot of assumptions on these forums and most are wrong. In the states 11mm uprated studs are the norm on big builds. They mostly use the arp625+ or LR19.
I have run my sprint car to over 550/550 on 11mm RCM extreme. When torqued to 90ftlbs no issues
My drag car has used 11mm cosworth bolts for years, just come apart again no gasket issues. Ran up to 2.7 bar!
Not saying 14mm isn't ever needed just that there are a lot of assumptions on these forums and most are wrong. In the states 11mm uprated studs are the norm on big builds. They mostly use the arp625+ or LR19.
03 March 2017, 01:49 PM
#34
For info
I have run my sprint car to over 550/550 on 11mm RCM extreme. When torqued to 90ftlbs no issues
My drag car has used 11mm cosworth bolts for years, just come apart again no gasket issues. Ran up to 2.7 bar!
Not saying 14mm isn't ever needed just that there are a lot of assumptions on these forums and most are wrong. In the states 11mm uprated studs are the norm on big builds. They mostly use the arp625+ or LR19.
I have run my sprint car to over 550/550 on 11mm RCM extreme. When torqued to 90ftlbs no issues
My drag car has used 11mm cosworth bolts for years, just come apart again no gasket issues. Ran up to 2.7 bar!
Not saying 14mm isn't ever needed just that there are a lot of assumptions on these forums and most are wrong. In the states 11mm uprated studs are the norm on big builds. They mostly use the arp625+ or LR19.
For a daily driver I would imagine there is more cyclical loading of the heads/studs/gaskets, for sure it took time and mileage on my car. It was contaminating it's coolant for 6-7 months and 1000s of miles before the H/G gave out last week and it overheated.
03 March 2017, 01:55 PM
#35
Scooby Regular
Maybe a difference of application, sprint and drag cars give all for a short time and then it's all over and do not cover as many miles, assuming you aren't driving them as dailys.
For a daily driver I would imagine there is more cyclical loading of the heads/studs/gaskets, for sure it took time and mileage on my car. It was contaminating it's coolant for 6-7 months and 1000s of miles before the H/G gave out last week and it overheated.
For a daily driver I would imagine there is more cyclical loading of the heads/studs/gaskets, for sure it took time and mileage on my car. It was contaminating it's coolant for 6-7 months and 1000s of miles before the H/G gave out last week and it overheated.
Out of those road miles how many are you doing on full chat? a sprint/drag car will be on full chat a considerably higher percentage of the miles.
Tootling along at 3 grand with no boost you'll get into several hundred thousand miles before you get issues. Its on boost and revs that put the load on the engine. It's why you see legacys and non turbo impreza's over 200k
03 March 2017, 03:17 PM
#39
For info
I have run my sprint car to over 550/550 on 11mm RCM extreme. When torqued to 90ftlbs no issues
My drag car has used 11mm cosworth bolts for years, just come apart again no gasket issues. Ran up to 2.7 bar!
Not saying 14mm isn't ever needed just that there are a lot of assumptions on these forums and most are wrong. In the states 11mm uprated studs are the norm on big builds. They mostly use the arp625+ or LR19.
I have run my sprint car to over 550/550 on 11mm RCM extreme. When torqued to 90ftlbs no issues
My drag car has used 11mm cosworth bolts for years, just come apart again no gasket issues. Ran up to 2.7 bar!
Not saying 14mm isn't ever needed just that there are a lot of assumptions on these forums and most are wrong. In the states 11mm uprated studs are the norm on big builds. They mostly use the arp625+ or LR19.
The cosworth and arp are known to cope, hence I bought the rcm1635 being assured they would be ok, maybe if they were torqued to 90 as per your advise instead of 70 quoted in instructions then I may have been ok as mine was a slight fracture near turbo head side, so not that bad.
03 March 2017, 03:39 PM
#42
Its no good guessing until its stripped out, it may well not be the head gaskets, a split liner could be an issue here also.
Were the heads & block faces skimmed on the rebuild ? what sort of finish of the skimming achieved ? were the head studs, if new, were run in on initial torqueing up ?
You also mentioned adding the wrong type of coolant, the Cosworth / RCM gaskets are very funny on the coolant you can run with them, it causes the outer finish of the gasket to pickle up, & detach from the steel layer.
As for gasket thickness, it will require the engine to cc'd to establish the compression ratio, as a rule, with std compression Mahle pistons fitted, block & heads skimmed etc, a 1.1mm gasket is the usual fitment to maintain std OE comp ratio.
Were the heads & block faces skimmed on the rebuild ? what sort of finish of the skimming achieved ? were the head studs, if new, were run in on initial torqueing up ?
You also mentioned adding the wrong type of coolant, the Cosworth / RCM gaskets are very funny on the coolant you can run with them, it causes the outer finish of the gasket to pickle up, & detach from the steel layer.
As for gasket thickness, it will require the engine to cc'd to establish the compression ratio, as a rule, with std compression Mahle pistons fitted, block & heads skimmed etc, a 1.1mm gasket is the usual fitment to maintain std OE comp ratio.
03 March 2017, 03:42 PM
#43
Maybe it depends if they are yield fit or not?
I'm discussing 14/12 conversion with them as I want some piece of mind and scope to up power in the future. By the time you factor in resurfacing, machining the conversion and that the 14/12s are cheaper than 11mm extremes it's only a couple hundred quid more.
Thinking I might fit some uprated rods as well since the engine is in pieces!
I'm discussing 14/12 conversion with them as I want some piece of mind and scope to up power in the future. By the time you factor in resurfacing, machining the conversion and that the 14/12s are cheaper than 11mm extremes it's only a couple hundred quid more.
Thinking I might fit some uprated rods as well since the engine is in pieces!
03 March 2017, 04:31 PM
#45
No problem.
A lot of views I read are hearsay on many subjects here. I've posted on this thread as I can offer genuine feedback based on the facts I know.
I have also run standard studs and gaskets on my old spare 2.5 sprint engine to 500/500 (1.6 bar) without gasket failure! That engine had no signs of gasket issues when I removed the heads.
So are studs the issue with failed gaskets? IMO no 90ftlbs (for 11mm studs) and proper mapping is the key.
I am moving to 14mm on the next sprint engine only because the block I have purchased is already converted, otherwise I'd be staying 11mm.
A lot of views I read are hearsay on many subjects here. I've posted on this thread as I can offer genuine feedback based on the facts I know.
I have also run standard studs and gaskets on my old spare 2.5 sprint engine to 500/500 (1.6 bar) without gasket failure! That engine had no signs of gasket issues when I removed the heads.
So are studs the issue with failed gaskets? IMO no 90ftlbs (for 11mm studs) and proper mapping is the key.
I am moving to 14mm on the next sprint engine only because the block I have purchased is already converted, otherwise I'd be staying 11mm.
03 March 2017, 04:48 PM
#46
Agree, I have also seen stock studs make 500+.
Thing is I had the 1635s which coincidentally are 350hp rated but was assured the seller has ran 500+ with them no problem, maybe the extremes may have been more suitable.
But I had been running circa 450hp on them and upto 2 bar so I'm at a head scratching sinario.
I'm also going 14mm just to forget about it and future proof myself.
Thing is I had the 1635s which coincidentally are 350hp rated but was assured the seller has ran 500+ with them no problem, maybe the extremes may have been more suitable.
But I had been running circa 450hp on them and upto 2 bar so I'm at a head scratching sinario.
I'm also going 14mm just to forget about it and future proof myself.
03 March 2017, 08:23 PM
#47
Well, the heads are off. RCM 1635 11mm studs were fitted, the ones rated at 350bhp on their website.
I think that's pretty clear!
The gasket material has bubbled, image attached, is this solely because of exhaust gases or possibly chemical attack by a small amount of different coolant I might have added, as was mentioned earlier?
I think that's pretty clear!
The gasket material has bubbled, image attached, is this solely because of exhaust gases or possibly chemical attack by a small amount of different coolant I might have added, as was mentioned earlier?
03 March 2017, 11:08 PM
#53
Hence why I believe the 1635 are no good for anything above stage 1 power.
That must of taken ages to get to that point, how long was it before first sign?
I pulled mine as i got sick of having to check coolant level before i drove it although was still running well
That must of taken ages to get to that point, how long was it before first sign?
I pulled mine as i got sick of having to check coolant level before i drove it although was still running well
04 March 2017, 12:09 AM
#54
Can I ask..are standard head bolts 11mm?
And why is the process for tightening different on the RCM instructions to how they are as per engine builders(the instructions I followed)?
The difference being,after slackening off all bolts by 180* then a further 180*(after this the RCM Instructions differ) :
Tighten top middle and bottom middle by 34Nm,tighten the rest(in sequence) 15Nm
Then in sequence tighten all by 90* then repeat 90*
So are aftermarket head bolts fitted and torqued up different to oem bolts?
If so then why?
And why is the process for tightening different on the RCM instructions to how they are as per engine builders(the instructions I followed)?
The difference being,after slackening off all bolts by 180* then a further 180*(after this the RCM Instructions differ) :
Tighten top middle and bottom middle by 34Nm,tighten the rest(in sequence) 15Nm
Then in sequence tighten all by 90* then repeat 90*
So are aftermarket head bolts fitted and torqued up different to oem bolts?
If so then why?
04 March 2017, 08:13 AM
#55
It's also down to the gaskets used, but the method is about even clamping force... Problem is there are so many variables in engine building... most relate to the person doing the job... their attention to detail is the real key here... you need to be properly OCD to be an engine builder... not just a guy with a box of spanners and lots of info. 
04 March 2017, 09:03 AM
#57
But you do say "do it right" which hints at perfectionist mentality.... which is part of being OCD... being OCD is not just making sure all your socks are ironed and lined up properly in a draw.
Everyone has their own ideas about what's right and what's wrong, so there's always going to be room for error/ mis interpretation, just the way it is.
04 March 2017, 09:12 AM
#58
Maybe so, 8 out of 10 times... here on this thread we see the other 2
But you do say "do it right" which hints at perfectionist mentality.... which is part of being OCD... being OCD is not just making sure all your socks are ironed and lined up properly in a draw.
Everyone has their own ideas about what's right and what's wrong, so there's always going to be room for error/ mis interpretation, just the way it is.
But you do say "do it right" which hints at perfectionist mentality.... which is part of being OCD... being OCD is not just making sure all your socks are ironed and lined up properly in a draw.
Everyone has their own ideas about what's right and what's wrong, so there's always going to be room for error/ mis interpretation, just the way it is.
This thread shows from my untrained eyes that heads haven't been put on correctly,I might be wrong
It's 6 bolts per head,even my 7 year old nephew could get that right
04 March 2017, 10:49 AM
#59
Scooby Regular
Can I ask..are standard head bolts 11mm?
And why is the process for tightening different on the RCM instructions to how they are as per engine builders(the instructions I followed)?
The difference being,after slackening off all bolts by 180* then a further 180*(after this the RCM Instructions differ) :
Tighten top middle and bottom middle by 34Nm,tighten the rest(in sequence) 15Nm
Then in sequence tighten all by 90* then repeat 90*
So are aftermarket head bolts fitted and torqued up different to oem bolts?
If so then why?
And why is the process for tightening different on the RCM instructions to how they are as per engine builders(the instructions I followed)?
The difference being,after slackening off all bolts by 180* then a further 180*(after this the RCM Instructions differ) :
Tighten top middle and bottom middle by 34Nm,tighten the rest(in sequence) 15Nm
Then in sequence tighten all by 90* then repeat 90*
So are aftermarket head bolts fitted and torqued up different to oem bolts?
If so then why?
ARP 11mm studs are similar.
There is a difference when using stud/nut combo as compared with bolts.
With Bolts you have to transmit the tightening torque through the whole length of the bolt to the cylnder head thread. With Studs the torque is only applied at the nut on top of the cylinder head.
Because of this Bolts tend to twist/wind up/pre-load and you tend to get more stiction at the bolt head/washer/cyl head interface. The reason for backing off and retightening and using the special lubricants.
If the thread in the head is dirty or damaged this will prevent the bolt achieving the correct torque.
Tightening procedure for 2.5L OEM bolts
1. Install the cylinder head to the cylinder block.
CAUTION:
Be careful not to scratch the mating surface of cylinder head and cylinder block.
NOTE:
Use a new cylinder head gasket.
(1) Clean the bolt threads and the bolt holes in the cylinder block
CAUTION:
To avoid erroneous tightening of the bolts, clean out the bolt holes sufficiently by blowing with compressed air to eliminate engine coolant etc.
(2) Apply a sufficient coat of engine oil to the washer and bolt thread.
(3) Tighten all bolts to 40 N·m (4.1 kgf-m, 29.5 ft-lb) in alphabetical order.
(4) Retighten all bolts to 95 N·m (9.7 kgf-m, 70.1 ft-lb) in alphabetical order.
CAUTION:
If the bolt makes stick-slip sound during tightening, repeat the procedure from step (1). In this case, the cylinder head gasket can be reused.
(5) Loosen all the bolts by 180° in the reverse order of installing, and loosen them further by 180°.
(6) Tighten all bolts to 10 N·m (1.0 kgf-m, 7.4 ft-lb) in alphabetical order.
(7) Retighten all bolts to 30 N·m (3.1 kgf-m, 22.1 ft-lb) in alphabetical order.
(8) Retighten all bolts to 70 N·m (7.1 kgf-m, 51.6 ft-lb) in alphabetical order.
(9) Retighten all bolts by 80 — 90° in alphabetical order.
(10) Retighten all bolts by 40 — 45° in alphabetical order.
CAUTION:
The tightening angle of the bolt should not exceed 45°.
(11) Retighten bolts (A) and (B) by 40 — 45°.
CAUTION:
Make sure the total “tightening angle” of steps (10) and (11) does not exceed 90°.
Tightening info for ARP 11mm studs
The "NOTE" mid page being highly significant
04 March 2017, 11:27 AM
#60
Good info Don Clark
I always thought when using the stud&nut option that the studs were fitted when getting block work done,I know different now cheers.
I just reused my old head bolts coated in engine oil which seemed to work well for me.
Am I right in thinking that an engine builder would always choose the stud&nut option over the bolt option?
I always thought when using the stud&nut option that the studs were fitted when getting block work done,I know different now cheers.
I just reused my old head bolts coated in engine oil which seemed to work well for me.
Am I right in thinking that an engine builder would always choose the stud&nut option over the bolt option?