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Low compression

R

Rob Z

Member
Well my rebult 302 is smoking. I also find the compression is low, about 105 - 110. I squirted some oil in one of the cylinders and compression went to 127 so it looks like a ring issue. The engine was rebuilt before I got it and set for at least 2 years. I did spray the cylinders with WD40 before I put the heads on, but did not remove the pistons. My guess is the rings are stuck and/or the oil seals are bad. When I run the engine my oil pressure pegs the factory gauge. I should have pulled it down while I had it out, but there goes that hind sight being 20/20 again.

So what are my options? Is there anyting I can try before I pull the engine and tear it down?

Asside from high oil pressure and smoking the thing purrs. Of course it is being well lubricated.

Thanks
 
I would get some Marvel Mystery oil and poor some in each spark plug hole. Cycle the engine to spread it out. Let it soak. Cycle the egine a few more times and run it for a while. May be stuck rings.....may be not broke in yet.....
 
I agree, don't tear anything apart yet. Marvel Mystery Oil is definitely a good start.

Are you checking compression with the engine warm? If the pistons are cast or forged, they expand quite a bit when they heat up.

As far as oil pressure goes, don't rely on the factory gauge/sender. Hook a mechanical gauge up to it and see what pressure it's actually running at.
 
The engine was rebuilt before I got it and set for at least 2 years.
Click to expand...


"Set for at least two years" without ever having been ran after the rebuild? As in.... it has not been broken in yet? Run it for 500 miles before thinking about tearing it down.
 
Things are getting better. Put Marvel Mystery in all cylinders. Let it set for several days, once a day turning engine over a few times to distribute the MM. Started the engine and ran at 1500 for 10 minutes where it smoked like crazy. Let it set for a day, then restarted with very little smoke. So now just need to get some miles under it.

Thanks :ecit
 
Sounds good. That Marvel Mystery Oil can be good. Hope the engine holds out for you now.
 
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