I was wondering what my final compression ratio is. According to the Jegs catalog with a 64cc head I will get 11.82 and with a 76cc I will get 10.22. Im using a 72cc head, what is my final comression ratio?

Justin

What size engine?

What is deck height?

What is dome volume?

Measured cylinder head volume?

Jegs made a lot of assumptions when giving you those numbers. What the assumptions are I don't know. Also, you can't assume that your engine will be built to exactly their specs, so your actual compression ratio will vary anyways.

But say for example you wanted an educated guess. From 64-76cc is a 12cc jump, yielding 1.6 points decrease in compression. Also, 72cc is 8/12 of the way between 64cc and 76 cc. So you can set up a ratio

8/12 * 1.6 = 1.066 (amount of compression decrease from 64cc to 72cc)

Giving you 11.82-1.0666666 = 10.75

But this is only a "rough" estimate so don't count on it being 100% accurate.

[ 07-23-2003, 03:15 PM: Message edited by: sik68 ]

Thats all I wanted was that rough educated guess. Nothing to technical. Thanks.

Justin

Its kinda hard to give even a rough guess without the info Eric posted. Kinda need to know what were working with here ;)

Originally posted by travis:
Its kinda hard to give even a rough guess without the info Eric posted. Kinda need to know what were working with here ;) Yeah, like what engine . . . you can't (or shouldn't) even guess without knowing the engine size . . .