crowbar73

I recently purchased an 89 gt automatic and wanted to to do a compression check on the cylinders to make sure they were no dead cylinders, etc. I can't find anywhere that will tell me what the compression should be in p.s.i. I only tested one so far and it was around 125 psi. is that good or bad?? Would appreciate any help.
P.S. the engine seems to run fine but would like to check anyway
Thanks in advance

vtecwho

when i did it, the ones i checked were at 150psi. i dont know how that would translate into ratios tho. from my test your test seems low

crowbar73

Thanks for the reply. It looks like you have done some work on your motor where mine (to the best of my knowledge) is bone stock. I wonder if that is where the difference comes from. I also talked to a friend that races on a dirt track & he says his motors pumped up to about 220-230. Higher compression ratio i suppose. Thanks again for the info, it's food for thought.

GreyStang

If you're just checking for a dead cylinder then just do a compression test on all the cylinders & write down the numbers. You should see an "average reading" (within 20-40 psi) for each cylinder, if one is super low compared to the others then there's your problem

Colorado_Mustang

My cylinders are only 100psi.

But, they are all there, and it runs pretty good up to 7k rpm (if I can keep the tires from spinning, anyway).

As Grey said, make sure they're all within about 10% of each other. If so, you're good. You can also do a leak down check.