Cosworth piston rings...
#1
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Cosworth piston rings...
I'm currently rebuilding my bottom end on my 2wd saph, I bought the bottoms end already bored .5 over bored and honed, I have measured the Pistons in the bore and its is .38mm which I beleive is a good tolerance? But when I put the Piston rings in, push them down the bore slightly with the piston and then measure the gap it is between 0.80mm - 0.97mm, the workshop manual says it should be 0.4 - 0.6mm, the rings are the correct 0.5 oversize so what is goin on??
Regards, Kieren
Regards, Kieren
#2
Instead of parts of numbers, make proper measurements.
And if you're trying to say you have a piston to bore clearance of 0.38mm which is 15thou in old numbers....then you really have a serious problem as that is huge.
And if you're trying to say you have a piston to bore clearance of 0.38mm which is 15thou in old numbers....then you really have a serious problem as that is huge.
#3
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Just reread my post, then went and re measured, the bore measure 91.41mm and the pistons measure 91.25mm, so that gives me a gap of 0.16mm or 0.0062 thou, is this acceptable in a 350bhp road car with hard use on 4x4 Mahle pistons?
Regards, Kieren
Regards, Kieren
#6
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Taking the block and Pistons down the machine shop tomorrow to have them properly measured. Fingers crossed!!
#7
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Ok so had it all measured up properly, worked out closer to 8 thou of clearance, so god knows what the block was machined for before?? Anyway, I have had the Pistons measured and they are 91.257 (they have had about 2k of use) and having spoken to Mahle they recommend a 91.32mm bore size which is what I will get my spare block bored out to, that would give me 0.0026 inches, is this good for a 350bhp road car?
Regards, Kieren
Regards, Kieren
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#8
If you spoke to Mahle and explained your build to them, surely they will know if that clearance is fine or not ?
8 thou certainly wouldnt have been though !
2.6 thou could sound a little tight, but you dont state piston material etc
8 thou certainly wouldnt have been though !
2.6 thou could sound a little tight, but you dont state piston material etc
#9
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They are standard Mahle 4x4 Pistons, but the book clearance for these and Mahles spec shows it should be 1.5 thou, so 2.6 sounds loose still, yet I have read e few threads on here with people quoting that it's too tight.
#11
PassionFord Post Whore!!
Mark
#12
I've found that life I needed.. It's HERE!!
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Regards, Kieren
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