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DDS DDS is offline
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Join Date: Dec 2000
Location: ON, Canada
Posts: 886
Compression ratio: What is the practical maximum?

I have set up my heads to run as high as 9.1:1 CR with a .040" (8.6 with .060") deck height, and a FAT442 cam.
I've read that 8.5:1 is a conservative max for a stock T4, yet other engines (even without knock sensors) run much higher than that on pump gas without problems.

What is the practical max. a street T4 can run on pump gas?
Does this become a function of the duration of the cam? (true versus static CR?)

I've read that deck heights are generally set at .040-.060" What is the maximum deck height one ought to run? Other than a lower CR, what problems are caused by excessive deck height?


TIA, Dave.
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'73 914, 2056 GT/SC done!
'69 Lotus Europa S2 - under resto.
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Last edited by DDS; 02-25-2002 at 05:38 AM..
Old 02-25-2002, 05:35 AM
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