WHAT SOULD THE COMPRESSION GAUGE READ ON A 1995 MUSTANG GT.WITH A COLD MOTOR.

 

It can vary. The biggest thing you are looking for is very close #'s between cylinders. The compression could be anywhere from 125-150 psi. Like I said you're looking for close comparison #'s. 5-15 psi difference between each one. More than that indicates a problem

 

OK..DONE MY COMPRESSION CHECK...

CYLINDER PSI

1 122
2 122
3 120
4 135
5 115
6 122
7 85
8 130

 

I did mine last week and ranged from 150 to 154. Looks like it is time
to pull the heads and see whats going on

 

Yeah, I'd say you have a problem on that #7!!!
Why do you say that?

 

If you want to find out if you have bad rings or bad valves, squirt some oil (30 wt) in that number 7 and check it again. If the comp reads higher, you probably have bad rings, if it says the same maybe some head work comming your way. Do that before you pull your heads, might save you some work. Mine checks out at about 150psi all around.

 

I did the oil thing with #7...It went 100 psi.

 

Well, that means bad rings, how many miles? Ford specs the comp as a min of 101psi. Looks like time to build or find a new motor. Sorry sounds like your motor is shot....anyway, I guess I could be wrong, maybe some other opinions?

 

The reason I said that was because the rings are shot on #7. Most of the
time Iv'e found with compression that low it has been rings.

 

Squirting oil into just one of the cylinders wont tell you jack. You need to do it with all of them. Yeah, of course the compression is going to go up. You need to see what kind of increase you get on the other cylinders when you squirt in oil. If it only goes up 5lbs then yeah, #7 may need rings, but if they ALL went up 10-15 lbs, where did this test get you?

Id invest in a leakdown tester to do further investigation. The 60$ will be well worth it when you consider how much time you would have invested by pulling the heads.

This is a good gauge, made in USA. I use this gauge, and I use retailer.

http://www.thetoolwarehouse.net/shop/STR-CLT2PB.html


Jim