Hi, I have searched the forum without any luck, but I guess this has been discussed somewhere before. I am about to pull the engine out of my Mistral before sending it off to the paint shop, and checked the compression yesterday. It's the first time using the equipment, and I haven't been able to find what would be normal, or good, compression for my engine. These are the results; C1: 100 psi C2: 90 psi C3: 90 psi C4: 100 psi C5: 100 psi C6: 80 psi Any thoughts on the results? The car has basically been standing since 1994, but starts on the first try and runs super smooth on idle.
Those numbers are low. Around 150 psi would be normal. Did you open the throttle when doing the compression test? Make sure to step on the accelerator when spinning the engine. If the compression value does not increase with the throttle open then put a little engine oil down the cylinders and test again. If the values increase significantly then the rings are worn, if they stay the same then it is the valves. Ivan
Be sure to open the throttle when doing a compression test, engine needs to breath freely. Your results are low IMHO. I'd hope for 140-160 psi. Try shooting a little bit of oil into each cylinder first. If compression comes up it's most likely worn, broken or stuck rings. If little change your valves are not sealing well, more or less. If your engine seems to run well (at least smooth) it'd be a tough call to say it's worth the expense for a rebuild. While your results are not up to spec. if your oil pressure seems OK I'd be inclined to, hmmmm---tough decision. How much has it been run recently? Rings could be bound up, might improve. "Italian Tune Up" (get it up to temp and thrash it a bit) might be in order. Of course do so AYOR!
IVAN, Great minds think alike. Actually your post missed my attention as I typed my response, my awareness maybe not so great!
Hey Alex! My first post here, though have been reading posts now and then. Your compression readings are very low, I hope you just forgot to push the throttle. Should be in the 140-150psi range, about the same as my Merak. A Biturbo can be as low as a 100psi, but that is a turbo engine, very different. Cheers, Jarle
