Compression test results poll (pre-2000 Gen II) . . .

[PhoenixGTS]

Please post your results from compression tests on pre-2000 Gen II engines and indicate if the test was wet or dry - and specifically what variances were seen between cylinders. Heck any Viper engine for that matter. I'm trying to develop a database of real-world numbers.

 

[MIKE-HKS]

you mean hot or cold?
do it cold remove all the plugs and open the TB hold them open and crank each cyl over 5 ,6 ,7times you can watch the gauge and see how many strokes it takes each cyl to reach max psi , wright it down and do all "10" like that

 

[PhoenixGTS]

you mean hot or cold?
do it cold remove all the plugs and open the TB hold them open and crank each cyl over 5 ,6 ,7times you can watch the gauge and see how many strokes it takes each cyl to reach max psi , wright it down and do all "10" like that

Well yeah, but what numbers/pressure is everyone ending up with and how consistent are the numbers/pressur between cylinders?

 

[lleone]

2001 GTS Ross Racing Pistons, 9.0:1 compression ratio, cold: 150psi +/-3psi

 

[PhoenixGTS]

2001 GTS Ross Racing Pistons, 9.0:1 compression ratio, cold: 150psi +/-3psi

Thanks for the feedback. I guessed well. I was thinking over 150 psi on stock pistons would be fine. The stock ratio is 9.6:1 correct? So a tight engine with stock pistons could maybe shoot for 160 psi or so? Very interesting to hear that the variance between cylinders was so tight.

 

[tommygun]

Acceptable variance from high to low is 15%, so it had better be tight. I have seen as high as 165 on a cold engine, and yes you said it right to start with, wet/dry. Compression does not generally change much due to engine temp. It can change drastically by injecting 1-2 tablespoons of oil into each cylinder, This is how one would determine whether a cylinder is weak due to a piston, rings or other cause, but will usually not effect a solid cylinder that has no trouble.

 

[PhoenixGTS]

Update. My car pumped 150 psi in 9 cylinders and low 140s in the 10th yesterday. Was concerned due to one exhaust port having a slightly lighter color than the rest and some "intelligence sources" comments that a previous owner had had a problem. If there ever was a problem, some one fixed it and I am having a great time hammering the throttle.

 

[Newport Viper]

My Gen1 was around 175, Why the difference?

 

[Jack B]

97 - 165 psi cold, no deviation