Commpression
Commpression
New User
Joined: Jan 2008
Posts: 0
Likes: 24
All users have 60 minutes to go back to their post and add or remove stuff.
Just ckick the EDIT button instead of post reply.
It's located at the bottom right of your posts.
Compression values change due to wear.
119 psi is okay as long as the difference between lowest to highest is no more than 15%.
That's where the problem exists.
EDIT:
When that engine was new it was probably about 140-150 psi
Just ckick the EDIT button instead of post reply.
It's located at the bottom right of your posts.
Compression values change due to wear.
119 psi is okay as long as the difference between lowest to highest is no more than 15%.
That's where the problem exists.
EDIT:
When that engine was new it was probably about 140-150 psi
Fleet Mechanic
Joined: Mar 2004
Posts: 1,398
Likes: 17
From: Hesperia, CA
Dennis is right, every time I post I read it at least 3 times Before I post it. But almost every time I read the reply I realize that I made a horrible spelling error or left something out, so I have to edit it.
As far as the compression reading go, if the are all within 10 percent then you are good to go.
As far as the compression reading go, if the are all within 10 percent then you are good to go.
Last edited by fasthauler; Jun 23, 2006 at 01:57 PM.
Cargo Master
Joined: Apr 2001
Posts: 2,364
Likes: 3
From: Eustis FL
Some books will tell you that as long as the lowest reading is within 75% of the highest cylinder reading, you are 'ok'. For example, if lowest is 90 psi, and highest is 120, then 90X100 (%) divided by 120 equals 75%. That is kinda pushing it, but the engine is probably still running ok at that point. If you are getting 119 all across, suspect fairly even wear among internal engine components. I have a 1977 Mercury Cougar with 351M that was at an average compression of 90 psi, all cylinders within 75% of one another. It hardly had any power left, but still ran great with no missing. Oil pressure was gone after very, very many miles, but the engine never failed. I retired the car when I found a 1974 Montego with a very healthy 400 in it, low miles, no rust. Swapped my mag wheels, stereo, exhaust, and other goodies as a direct swap into it!
