Can someone tell me what the compression for a 1984 Z 28, 5.0 High Output, 5 Speed Manual Transmission was from the factory? I recently had my compression tested & the GM dealer stated my readings were between 140 & 145. He didn't give me a break down as to what the readings were per cylinder & at the moment he did not know what they were from the factory. He just stated that was pretty good as the newer cars are about 170! WTF!!! I would have thought he'd have known this before he called me. Is 140-145 good or should I be prepared to do some engine work before I paint the car?
Thanks!

 

no would say that pretty good, as long as there within 5% of each other liek u stated u should be fine, not sure what the factory compression is supose to be but on my 91 i got 150-155 all the way around

 

Thanks!

 

The static compression is only like 8.5:1 on this engine. My 84 was also in this range, 140psi. As mentioned the important thing is the difference between the cylinders. If you have some concern, like lost of power, high crank case pressure, or oil burning, when you should also get a leak down test done. This will give you an indication of the condition of the piston rings and valve seats.

 

I have no loss of power, no high pressure from the crank case nor am I burning oil, in fact the Chevy Service Manager was somewhat impressed with the car when he drove it. He thought it had plenty of power. What kind of difference between the cylinders should I be concerned with? The service mgr. did not elaborate on which readings came from which cylinder, he just said I was in between 140 & 145 across the board. The car has 120,000 miles on it. I did not know you could get a "leak down" test done. I m definetly going to check in to this, I wonder what's involved & if it's very costly? Anyway, thanks for your input!!

 

If you are between 140 and 145 across the board, then you are in good shape - no worries.

- Justin

 

If your not having any problems, STOP WORRYING, and go out and enjoy the drive!

 

Very good point dude! I'm just having the car painted & wanted to make sure all is well with the drive train before I paint the thing. Knowing my luck, after I get "her" all newly painted, I'd drop a cylinder or something..but from the feedback I've received from you folks, I'm worry free! Thanks again!!

 

By the way, nice choice. This is how my 84 started life. 305, 5 speed, 3:73 rear, 4 wheel dics., and all the HiPo stuff available that year.
Post some picts. when it's done.