I checked my compression on my Firebird today & I also fixed the accelerator problem too plus I installed new plugs & a fuel filter & boy it runs even better. Here are the results, are these good?

Cylinder #1 : 140 psi
" " #2 : 140 psi
" " #3 : 130 psi
" " #4 : 140 psi
" " #5 : 130 psi
" " #6 : 140 psi

Bare in mind that my car is an '86 Firebird w/ the 2.8L w/ 130,248 miles. Thanx

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- Mike Harvey -
1986 Firebird S/E

 

Yes there is less than 10% differnce so that is not bad. You might want better but consdidering the age and miles it must have, its in good shape.

 

Just to expand on what Kyle said. When looking at compression, look for evenness. If new it was say 160 (Out of the air) and they are all around 135 its ok. They are wearing evenly. So you dont have to worry about a blown head gasket, cracked head, etc, Basically the integrity of the cylinders is ok.

If on the other hand, you and a difference of say 50psi then that should be cause to worry.

A good rule of thumb, as Kyle said is 10% difference.

Clayton

 

Kyle and El Guapo are completely correct. It's the consistency from cylinder to cylinder that you're looking for in a compression check (As well as overall cylinder health, of course.)

Now, have you done a leak down? Cylinder compression only tells you part of the story.

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Maroon '92 RS 3.1L AT PW PDL CC Tilt

 

What exactly is a leak down & what does that do or tell me? Thanx

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- Mike Harvey -
1986 Firebird S/E