Compression Test
Fyter87
08-15-2005, 02:33 PM
I have 68 Nova with a L6 and I ran a Compression Test and all my Cylinders were at 145 PSI. I just wanted know how good that was or is it not that great?
Also I took out my spark plugs and most of them have white around the electroide and some black build up probably carbon.I only have about 4000 miles on the plugs too. Is this a sign that my timing could be off. or what? Plus I get alot oil around the threads on some of them. I cant figure that out either, becuase I dont have an oil leaks.
-Thanks for any help in Advanced.
Also I took out my spark plugs and most of them have white around the electroide and some black build up probably carbon.I only have about 4000 miles on the plugs too. Is this a sign that my timing could be off. or what? Plus I get alot oil around the threads on some of them. I cant figure that out either, becuase I dont have an oil leaks.
-Thanks for any help in Advanced.
AlmostStock
08-18-2005, 09:51 PM
Compression readings will vary depending on engine variables like compression ratio and camshaft timing. What might be low for one combination may be ok for another. One thing that always remains constant is all cylinders should be close to the same, and you got that going for you. For your 6 cylinder I'd say 145 is within the normal range.
I had a '68 6 cylinder Nova that I drove for like 10 years and 13X,XXX some miles. It was one of my favorite daily drivers.
I had a '68 6 cylinder Nova that I drove for like 10 years and 13X,XXX some miles. It was one of my favorite daily drivers.
MagicRat
08-19-2005, 09:59 AM
The most important thing about a compression test is consistency. If all cylinders are within 10% of the highest cylinder, the engine is in good shape.
If all your cyls read 145, thats excellent, and is quite high for an older engine.
As for the other 2 problems, your engine may have slightly worn valve guides or valve stem seals. A bit of oil is leaking down into the cylinders when the car is parked. When you start the car in the morning, do you get a little puff of blue smoke out the tailpipe?
Seals are quite easy to replace, on the engine. Worn valve guides require a head rebuild.
However, since your plugs don't seem to be too bad after 4000 miles, and you do not complain about having to add oil to the engine, I don't think the problem is worth fixing just yet. A little bit of oil seepage will not cause any harm. That engine has many, many more miles left in it as-is.
If all your cyls read 145, thats excellent, and is quite high for an older engine.
As for the other 2 problems, your engine may have slightly worn valve guides or valve stem seals. A bit of oil is leaking down into the cylinders when the car is parked. When you start the car in the morning, do you get a little puff of blue smoke out the tailpipe?
Seals are quite easy to replace, on the engine. Worn valve guides require a head rebuild.
However, since your plugs don't seem to be too bad after 4000 miles, and you do not complain about having to add oil to the engine, I don't think the problem is worth fixing just yet. A little bit of oil seepage will not cause any harm. That engine has many, many more miles left in it as-is.
Fyter87
08-21-2005, 09:53 PM
Yea, I do get sometimes a cloud of smoke in the morning. I did have some oil leaks around the valve cover at first, but I replaced the gasket and that solved the problem. Do you think I should go ahead and replace the seals. I mean the engine runs fine, im pretty sure it was re-built, but the guy I bought it from didnt know either. Right now it has. 110,000 miles on it, but im pretty sure it was re-built, becuase 145 PSI is pretty good. Thats good to hear though. Thanks Guys!! :)
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