compression ratios

Greener101 · Post by **Greener101** » Fri Aug 17, 2012 2:10 pm

What compression ratios are produced in a CA77 305 beginning with standard and continuing to max overbore?Greener

conbs · Post by **conbs** » Thu Aug 23, 2012 11:49 am

I think standard bore is 8.2:1. A little higher for the 250.

Greener101 · Post by **Greener101** » Fri Aug 24, 2012 1:10 am

Thanks for that reply.I seem to remember that stock was 8.2/3:1.Now if someone would add to our list the other ratios.Greener

Ford Guy · Post by **Ford Guy** » Fri Aug 24, 2012 5:32 am

Over bore usually doesn't have an impact on compression ratio. What changes it is the size/shape of the dome of the piston. I do not know if Honda ever made higher compression pistons but I know back in the day several aftermarket piston makers did. I am not sure what is available anymore. Hope this helps.

Jon

G-Man · Post by **G-Man** » Thu Aug 30, 2012 12:15 pm

If the starting C/R is 8.2 for these engines (I'm not sure) then the regular oversizes would give these CR increases. Bigger bore means bigger swept volume but the compression space in the head stays largely the same.

Bore C/R

60.00 8.20
60.25 8.26
60.50 8.32
60.75 8.38
61.00 8.44

G

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compression ratios

compression ratios

305Compression Ratios