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Can carbon buildup on psitons/heads increase compression?
I'm starting to research an engine rebuild. I hear that tiny variances in head/piston clearance will change compression, from say 9.3 to 1 on my SC engine to 9.8 to 1 (Euro spec). I've heard we're talking about a distance on the order of magnitude of a gasket. Maybe .5mm or so is all it takes. True?
If so, I'm guessing there's at least a few hundred microns of carbon between my heads and pistons. It would seem that if compression can be changed by such small distances between head/piston, carbon buildup would have an effect on compression over time. Anyone heard of compression increasing over time as a result of this buildup? Just curious.
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1979 911 SC Silver 2002 996 race car 2005 Ford Excursion |
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06-09-2008, 02:12 PM
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Join Date: May 2004
Location: Lake Cle Elum - Eastern WA.
Posts: 8,417
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Absolutely - That's why some older engines "diesel" and continue to run after they are shut off. The heat and compression causes pre-ignition. Was a bigger problem in the older days with poor fuel, weak spark and engines that burned more oil.
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Bob S. 73.5 911T 1969 911T Coo' pay (one owner) 1960 Mercedes 190SL 1962 XKE Roadster (sold) - 13 motorcycles |
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06-09-2008, 02:16 PM
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Senior Member
Join Date: Mar 2000
Location: Lacey, WA. USA
Posts: 25,309
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Like Bob says, the short answer is "yes."
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Man of Carbon Fiber (stronger than steel) Mocha 1978 911SC. "Coco" |
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06-09-2008, 02:30 PM
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2015 
