Hey everyone, looking for advise.. Ran compression check yesterday on my new 76 Highboy with a 390.. She smokes pretty bad off and on from the passenger side.. Averages about 110psi all except for the #2 cylinder also that was the only plug that had oil on it.. So I checked #2 a few more times and it would fluctuate?? So I brought it to TDC hooked up my air and sure enough getting some air coming out the oil filler.. Rings!!! ugh.. My question is 2 parts...

Could it only be smoking sometimes due to the rings maybe being set correct and then back in place? Would this also be the variations i seen in the compression test?

Thinking of just putting in a Long Block from Napa or somewhere else, Thoughts on those crate motors..

Thanks,
Chris

 

It could be the rings or also leaking compression around a valve and oil down the valve guide. One test is to squirt a good shot of oil in the spark plug hole (?1/2 to 1 tsp). The oil will temporarily seal the rings. If the compression test comes up with the oil, that suggests rings.

I have never bought an AP store long block... from what I see though, their reputation is pretty mixed. I believe Jasper engines does a better job but likely more costly.

 

Thanks for the response I appreciate it..

 

Did you do a leak down test on any other cylinder? How much air was coming out the dip stick hole? All pistons will leak some air by them so knowing that what air was going past #2 is only useful if it was noticeably more air than the other cylinders.

If #2 is bad... How many miles are on your motor? It could easily be that a ring or piston broke or cracked (you could just have a hole in a pistons) and maybe it just needs a hone and a new piston and rings for #2. I'd say it's time to investigate some more and figure out what you need.

On the subject of a auto parts store long block, I'd look around at some local machine shops and see how the costs compare between a long block and rebuilding your own. A good machine shop will put much more care into your new motor and allow you to select better than factory parts.

 

Thanks 69, yes we ran air down other cylinders and the air was much more from #2 and #2 was the only one with oil caked on the plug..

I was thinking long block for a couple of reasons... I live in a small town so machine shops are limited and this is my daily driver. Long block would be quick and have a warranty. Also I know they're prob not as good as a custom build but one would think they would be good overall motors..... I am driving it now until I get the cash together, just the smoke is irritating at times....