Volume X, Issue 11, Page 91


If a compression test reads different on one side than the other, 190 versus 170… will that affect it much and what can cause that and how can I fix it? I don't know what to do.

Jerry Aguirre
El Paso, Texas

The way you phrased your question indicates that ALL the cylinders on one side are at 190 psi and ALL the cylinders on the other side are at 170psi? If that's the case that is a little weird. It is not uncommon for every cylinder to vary as much as 15-20 psi on a used engine depending on the type of rings used, piston clearance, valve seat concentricity, etc. But if they are ALL the same on one side I don't have a answer for you as to why. I will say though that a difference of 20 psi from side to side wont hurt anything. You are simply down a small amount of power on the side with 170 psi. Hope this helps. 

Jay Roeder

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