Whats your cranking PSI?

[Fopar]

Just did a compression test, most averaged at 140-150, one was down at 125ish , what is it roughly on a stock motor?

 

[Fopar]

bump

 

[go-stang5.0]

That sounds about right...most guys get about that or a bit less on the stock motor. Yea the 125psi cylinder is a bit low compared to the others but its not too bad. you could try that restore stuff....

 

[BlueOvalStangGT]

140-150 is ok, 125 isnt very good. How stock of a motor is it?

 

[Fopar]

unknown how stock, it either has CPU mods or a cam cuz it's a dog below 3k... the heads were supposedly redone just before I bought it, short block has 145k on it.

 

[go-stang5.0]

for a 145k shortblock thats not bad at all. I'd maybe try some of that restore stuff and just run it till something blows up.

 

[HISSIN50]

There are so many variations in methods for procuring the results that it's not real worth worrying about absolute numbers (if your engine wasnt warm for instance, that can make a decent difference).
The spread is what matters.
I'd do a wet test on that low cylinder and see if it jumps right up to the spec of the other cylinders when they also are tested wet.

Good luck.

 

[Fopar]

well I ran the test cuz it got hot recently, stupid fan connector was messed up and sometimes fan wouldn't come on. Was in traffic and noticed the gauge was 3/4 way up so pulled off and sure enough the fan wasn't on. Wiggled it and got it to come on but the thing was too hot, puked alot of water out and would not cool down. Got it off the road and let it sit off for a while then poored some water over the rad to cool it. Then started driving to a friends house about 2 miles down the freeway and it started getting hot again . By the time I got to friends house the gauge was in the red. Shut it off for a good long time this time, filled the radiator and replaced the fan with one off a parts car I have. No more cooling problems but I was worried I might have hurt the motor. It seems a little down on power but nothing I can quantify for sure.

There's no dead cylinders as the compression test shows, but not sure if I may have warped an exhaust valve on that one cylinder (or maybe head surface). Anyone here ever overheat?

 

[Fopar]

test was run after a long freeway drive with lots of WOT . I checked the temp after I did that cylinder and it was around 190 still. I only did one side of the motor at a time to make sure motor was warm. Test was done with throttle wide open

 

[HISSIN50]

If you think you are bleeding pressure, do a leakdown. This should show you real quick if you're bleeding pressure off.

Personally, I'd not really worry. For a motor with that kind of age, a cylinder that's 15 PSIG low isnt a super huge deal (it is to enthusiasts, but not to guys who need a DD).