new forged engine piston slap
#1
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new forged engine piston slap
hi
ive just recently had a forged engine buid, only done 300miles running in, ive noticed a rattle on start up from cold which goes as the engine warms, ive been told by the engine builder that its piston slap and is to be expected with forged pistons, do i have to live with this and is it normal?, i paid alot of money for this build and dont want to be taken for a ride and just want the engine to be right.
thanks
ive just recently had a forged engine buid, only done 300miles running in, ive noticed a rattle on start up from cold which goes as the engine warms, ive been told by the engine builder that its piston slap and is to be expected with forged pistons, do i have to live with this and is it normal?, i paid alot of money for this build and dont want to be taken for a ride and just want the engine to be right.
thanks
#2
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A small amount of piston slap is okay, if it becomes excessive i'd be having a word... the exact reason behind it being okay i'm not sure of, but i'm sure someone will be able to confirm. I was told the same thing by Harvey, Darren and Bob Rawle after mine was rebuilt with all forged internals... and i've 110% confidence in their work and knowledge.
#3
pistonslap is to be expected with a forged motor. the forged pistons will expand when they get warm and fill the bore. so long as it doesnt use oil forget about it.
#4
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Forged pistons are usually installed with greater clearance than cast pistons. The expansion rates between the two are different and more cold clearance is required for forged to ensure good running fit when up to temperature. You only need a extra thousandth of an inch clearance to make the engine noticably noisier!
In a forged piston set up, I would be a bit concerned if there wasn't at least a bit of slap when cold!
Gentle acceleration until up to temp.
JohnD
In a forged piston set up, I would be a bit concerned if there wasn't at least a bit of slap when cold!
Gentle acceleration until up to temp.
JohnD
Last edited by JohnD; 18 February 2010 at 11:06 AM.
#5
Normal - I thought my forged (RCM) engine was fecked when i first started it, but when the oil gets to circa 75C it goes quiet, but that's a good 5 minutes after the oem water guage gets up to the normal range in these temperatures. As above take it easy until fully warm.
#7
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This is completely normal.
All the above points are true, Forged pistons require a greater piston to bore clearance as they expand more when hot.
OE Pistons and some forged pistons have offset pins which will reduce noise. Most aftermarket pistons dont and together with the clearance required will be significantly more noisy than the OE piston.
As mentioned above oil cosnumption is key. If the engine isnt using alot of oil then you have absolutely nothing to worry about.
All the above points are true, Forged pistons require a greater piston to bore clearance as they expand more when hot.
OE Pistons and some forged pistons have offset pins which will reduce noise. Most aftermarket pistons dont and together with the clearance required will be significantly more noisy than the OE piston.
As mentioned above oil cosnumption is key. If the engine isnt using alot of oil then you have absolutely nothing to worry about.
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#10
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Well done for not jumping the gun and naming the engine builder before you were informed that everything was ok. That is the usual form, then a 20 page thread ensues, where everybody slags all engine builders, then the thread gets locked. A nice change from the norm.
Glad your mind is at rest.
Glad your mind is at rest.
#11
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my engine builder is highly respected on scoobynet, and naming and shaming was never really on my mind, i just wanted a few opinions on the rattle i have experienced just to put my mind at rest as im not an expert with engines, im happy with what im being told is quite normal, so i can now drive my car without any worries and continue the running in.
thanks
thanks
#12
does anybody know the bore clearance if using forged pistons? i just took apart my standard ej20 block and while searching online for pistons i found out there are about 3 sizes. 92mm, 95 and 99 as i remember. how should i go about selecting a piston for me? Help pls
#13
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does anybody know the bore clearance if using forged pistons? i just took apart my standard ej20 block and while searching online for pistons i found out there are about 3 sizes. 92mm, 95 and 99 as i remember. how should i go about selecting a piston for me? Help pls
Your engine will have a 92mm bore so you would choose pistons with that nominal diameter. The recommended clearance will be accounted for by the manufacturer in production. If you have the bores honed then you will need to discuss this with the piston supplier.
JohnD
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Building an engine you measure everything, 1 of them is bore clearence. Forged pistons manufactureres usualy recommend 3 1/2 thou clearence, however I run a larger clearence on my competition engines.
Rule is when warm the noise is gone.
Old group a wrc engines I used to build where noisey as hell even when warm, but they flew. F1 engines I used to build run a very tight clearence but try and hear slap off one of them on fire up!!!!
Rule is when warm the noise is gone.
Old group a wrc engines I used to build where noisey as hell even when warm, but they flew. F1 engines I used to build run a very tight clearence but try and hear slap off one of them on fire up!!!!
#15
mines a 2001 jdm ej205 engine and it had been idling in one place for almost a year and when dismantled i saw a few corrosions had eaten away a small lump from the bore at the bottom where the piston had been. this is only on one bore. so i decided to go forged since i have dismantled the engine. the problem is whether i should hone all the bores to match until the dissolved patch levels up in the damaged bore or else to bore to a specific level like around 0.25mm or 0.50mm. My subaru agent warned me not to bore above 0.50mm piston ring size. The other option is whether to resleeve the damaged bore only and hone that to match the others and buy forged pistons to match that clearance.
If iam to hone the block to match std pistons which holds 0.50mm rings then which piston size should i use if iam going forged? is it 95 or any other size? iam confused at this area regarding these sizes so am halted and cannot proceed further until i know what iam doin and what should be done. HELP! :-O
The other thing is that iam looking at producing around 400 to 450bhp. without using a stroker kit which turbo should i go for? which would you guys suggest from the following?
*T3/T4 T04E Hybrid Floating Bearing Turbocharger .50 A/R .63 A/R (30+ PSI, 500+ HP Capability)
*TDO6 20G
*T70
*GT30
*GT3582R .84AR
*GT45
*VF36
If iam to hone the block to match std pistons which holds 0.50mm rings then which piston size should i use if iam going forged? is it 95 or any other size? iam confused at this area regarding these sizes so am halted and cannot proceed further until i know what iam doin and what should be done. HELP! :-O
The other thing is that iam looking at producing around 400 to 450bhp. without using a stroker kit which turbo should i go for? which would you guys suggest from the following?
*T3/T4 T04E Hybrid Floating Bearing Turbocharger .50 A/R .63 A/R (30+ PSI, 500+ HP Capability)
*TDO6 20G
*T70
*GT30
*GT3582R .84AR
*GT45
*VF36
#16
Using alot of oil
Hi guys, I have a Wrx hatchback and it's running forged pistons and it's used 5L of oil in 3500 miles which I think is Alot, I took it back to the builder and they said its normal for it to use and needs a catch can to lower the consumption. Is that about right or is something wrong?
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Sounds like something is VERY wrong to me 5L in 3500 miles IS excessive and anyone that says otherwise is talking out of their rectum.
Return to sump catch can would reduce it... 'slightly'... but ultimately with those kind of consumption levels... something is not quite right.
Mind you at least you won't have to change the oil... as the engine is doing it for you.
Return to sump catch can would reduce it... 'slightly'... but ultimately with those kind of consumption levels... something is not quite right.
Mind you at least you won't have to change the oil... as the engine is doing it for you.
#21
Sounds like something is VERY wrong to me 5L in 3500 miles IS excessive and anyone that says otherwise is talking out of their rectum.
Return to sump catch can would reduce it... 'slightly'... but ultimately with those kind of consumption levels... something is not quite right.
Mind you at least you won't have to change the oil... as the engine is doing it for you.
Return to sump catch can would reduce it... 'slightly'... but ultimately with those kind of consumption levels... something is not quite right.
Mind you at least you won't have to change the oil... as the engine is doing it for you.
#25
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