Compression test on 7.8:1 engine

[doffo25]

Ive just performed (and repeated) a pressure test on my US spec car and got these results.

Bank A 95 95 87 95 93 100
Bank B 110 112 115 115 108 110

(squirting oil in cyl A3 increased it to 95psi)

Although fairly consistent between each bank Bank A is consistently lower that Bank B

Ive rebuilt the carbs and set the tappets but not yet tuned it. Could the lack of tuning cause this or what else could cause one bank to be consistently higher?

Also my gauge is a cheapo so psi results may be low but what psi should be expected for a 7.8:1 engine?

Is the ballpark atmospheric pressure x comp. ratio a good expectation ie

7.8 x 14.5psi = 113psi.

I would really like to remove head except Ive read too many horror stories re corroded studs!

thanks

David Offord

[Gfhug]

David, please read some of the topics listed below as there are good discussions of what to expect from compression tests. Your expected figures look low compared to suggested in one of those topics but I have no experience with the V12. You’ll also see that lack of tuning doesn’t seem to be of concern. Sorry I can’t help further but they should give you a good start.

Geoff

[Tommd]

Since you have some doubts as to the accuracy of your gauge, it may be a worthwhile investment to obtain a new one before you go to the time and expense of removing the heads.
As to low compression on one side, I wonder if that side cam could be slightly out of time, causing the issue.
Tom