Cylinder Compression

I'd say anywhere in the 45-60# range is fine depending on engine age.. The main concern is that all cylinders test fairly close to each other[ like within 5#].. Also, not all gauges will read the same..
 
Last night I tested a new engine with 3.5 hours running time.
The result was 60 psi +/- 1 psi. (61...59...60...60) Standard head.

I tested a well used engine last weekend for a gent whose family has owned the car since 1978. The results: 60..32..60..59. Standard head.

My touring engine tests at: 79...80...79...79 (6:1) Head

The cylinders should test within 10% (max) difference between them. So at about 60# average, (10% of 60# = 6# so 60-6=54) the lowest should be about 54#.

Obviously the low test of 32 mentioned above was not near what it should be. Surprisingly though, the engine ran pretty smooth and had sufficient power to move the car along well.
The owner elected to do nothing until the car stopped running well.
I agreed with him.

Dave in MN
www.durableperformance.net
 
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Yes-I have heard the within 5# rule as well. Can anyone explain the impact of having the pressure off by 10# on one cyliner
 
"Can anyone explain the impact of having the pressure off by 10# on one cyliner"

The engine may not run smooth with that difference....plus a minor amount of power loss.
Dave in MN
 
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Dave in MN said:
"Can anyone explain the impact of having the pressure off by 10# on one cyliner"

The engine may not run smooth with that difference....plus a minor amount of power loss.
Dave in MN
Click to expand...


uneven pressure on the crank, Creating an out of balance engine and wear on the bearings.
 
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