craiger

Recently I posted questions about oil comming out by breather valve and onto my valve covers. I can feel air comming out the pvc hole when i dissconnect it and i step up the rpms. I did a compression check and i am at a steady 170 psi. What is normal psi for our cars? My car is a 91 Z 28 with a 350. Any help would be GREATLY APPRICIATED

RB83L69

There is no real "normal". There are alot of factors that affect what the gauge will show. Just about anything from 150 to 180 is "noraml". As long as all cylinders are within 5% or so of each other, then the motor is probably healthy. Consistency is more important than the absolute value.

I'd say if you got 8 readings all between 165 and 175, your engine is probably in decent shape. If you had 7 cylinders at 165 and one at 175, that might indicate a bad cam lobe; 7 at 175 and one at 165 might show a leaky valve or set of rings; 6 at 175 and 2 right next to each other at 100 might indicate a bad head gasket, etc.

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"So many Mustangs, so little time..."
ICON Motorsports

ede

like rb said 140 to 180 is about right, the big thing is that the numbers are within 10%

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ICON Motorsports
1st & 3rd
MM Black Diamond 538 F&AM

craiger

I have a lot of work a head of me!!!! becuse one cylinder is reading only 120 psi where as the others are at 170psi. I put 5cc's of oil in the lower psi cylinder and it increased up to 155psi....need an overhaul so i gotta tell the wife Anyhow, i guess i'll be needing some suggestions for the rebuild. Thank you all for the help!

Duke901

So what does it mean when u have 1 cylinder at 120 and the rest are at 175 or if u have two low pressure cylinders next to one another while the other cylinders pressures are high

8Mike9

Never mind, didn't see your last post.

[This message has been edited by 8Mike9 (edited August 22, 2001).]