compression ratio and skimming heads. How much? - Alfa Romeo Forum
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(Post Link) post #1 of 3 Old 06-06-11 Thread Starter
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compression ratio and skimming heads. How much?

I have a 1988 164 V6 3.0 12v Sport. I wish to skim the heads to increase the compression ratio.
How much can I safely get away with skimming please? I've seen suggested 0.44mm. Is that right?
I've never, ever heard my engine pink under any circumstances even with crappy petrol, towing at high speed, high revs. So I think I can get away with increasing the ratio within reasonable limits. The SZ had the same engine with higher comp ratio, afterall.
I realise the best way to do this is to replace the pistons instead but I have a very limited budget and Hi-comp pistons are way out of my price range. Unless anyone happens to have a s/hand set they would want to sell me cheap?
Thanks
Tom
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Hi Tom with the motors you gain approximately 1cr per 1mm the piston rise in comparison to the head.
You can have your Gudgeon pin offset 0.8mm higher and remove 0.5mm from the head if they are still standard. If I remember correctly 1mm is the most advisable you can take from the heads.
As a safety precaution I will suggest that you have the pistons pocketed by 1mm to ensure that you will not have collision’s between them and the valves.
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(Post Link) post #3 of 3 Old 12-06-11 Thread Starter
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thats useful to know. Thankyou very much. Exactly what I was hoping for! I'll make sure to remove no more than 0.5mm I think. Many Thanks
Tom
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