Compression Test Results - Good/Bad ??
Thread Starter
Burning Brakes
Joined: Mar 2001
Posts: 1,228
Likes: 17
From: Mansfield Texas
Compression Test Results - Good/Bad ??
Having some problems with my 418 Iron Block Stroker that is in my 99 VERT. Have signs of coolant leakage under the valve covers and can not seem to troubleshoot an apparant vacuum leak that is causing my short and long term fuel trims to be excessively high.
Decided to perform a compression test across the board to see if my cylinder pressure is where it needs to be. I have no idea where the compression figures should be but here is what I achieved when tested:
2 - 130
4 - 125
6 - 142.5
8 - 142.5
1 - 137.5
3 - 137.5
5 - 142
7 - 137.5
Now I would like to perform a leak down test to check for ring seal. Come someone let me know how to do this.
Any ideas on where you think the water is getting in and why my fuel trims are out of whack is greatly appreciated.
Decided to perform a compression test across the board to see if my cylinder pressure is where it needs to be. I have no idea where the compression figures should be but here is what I achieved when tested:
2 - 130
4 - 125
6 - 142.5
8 - 142.5
1 - 137.5
3 - 137.5
5 - 142
7 - 137.5
Now I would like to perform a leak down test to check for ring seal. Come someone let me know how to do this.
Any ideas on where you think the water is getting in and why my fuel trims are out of whack is greatly appreciated.
Heel & Toe
Joined: Dec 2005
Posts: 15
Likes: 0
From: Plano Texas
good rule of thumb is
(worst compression x 100) / best compression =
100%-xxx= how much compression you are down. 25% is usually the benchmark you see as beeing 'no bueno'
so, in your case
(125x100)=12500/142.5=87.7
100-87.7 means you are only down 12.3 percent, which is not bad, but that is assuming that the 142.5 you pulled off 6 and 8 is 100%. again, i'd want to see 170-180 psi off a healthy ls1.
good luck
(worst compression x 100) / best compression =
100%-xxx= how much compression you are down. 25% is usually the benchmark you see as beeing 'no bueno'
so, in your case
(125x100)=12500/142.5=87.7
100-87.7 means you are only down 12.3 percent, which is not bad, but that is assuming that the 142.5 you pulled off 6 and 8 is 100%. again, i'd want to see 170-180 psi off a healthy ls1.
good luck
