Leaking Oil Filler Cap
 

Why in the world would an oil filler cap leak? I've replaced it twice and it still leaks. I cleaned the engine and added the fluorescent die and this is what I found. The oil is not coming from the cover bolt that is lit up, just pooled there first. For a moment I thought I had a tiny hole/crack in the valve cover just below the filler hole but there is no prior damage that I can see. funny thing is I didn't find any die on the cap. completely unrelated but I did find I have gas in the oil from a rich running carb.

Any thoughts?

Re: Leaking Oil Filler Cap
 

The hole in the valve cover that it spins in to is probably bent or warped from the cap being removed over and over again over 40 years. Also there should be a rubber gasket on the cap.

Gary

Re: Leaking Oil Filler Cap
 

Could also be due to blow-by. How worn is your engine? Is your PCV valve clean, and flowing well?

Re: Leaking Oil Filler Cap
 

The gasket on the cap is in place. As far as I can tell the engine runs great. no smoke, quiet, pulls strong... It was rebuilt about 10K ago. The PCV rattles which is how I've always been to check. I'll take a picture of the opening in a bit. Thanks!

Re: Leaking Oil Filler Cap
 

I have seen fuel diluted oil vapor escape the rubber gasket and collect on the rocker covers before.

Suggest you change your oil and filter, but fix that flooding carb first...

Make sure the oil filler cap fits tight against the cover....
and make sure the PCV rubber is soft enough to seal against the pCV valve...

:chevy::chevy::chevy:

Re: Leaking Oil Filler Cap
 

On the valve cover, rearward of the filler cap, there appears to be some sort of valve with a large rubber hose connecting possible to the air cleaner.
The other valve cover should have a PCV valve connecting to a vacuum source from either on the carb or directly from the intake manifold.

What is that thing on the valve cover?

Re: Leaking Oil Filler Cap
 

That is a flame arrester. It is part of your PCV system. More info on this thread
http://67-72chevytrucks.com/vboard/s...d.php?t=706115

Re: Leaking Oil Filler Cap
 

Thanks for the info, this has been very helpful. Based on the combined symptoms I'm betting on the fuel diluted oil vapor. The thing that ticks me off is I replaced the original quadrajet with a supposedly "plug and play" Edelbrock performer carb. I think my next chore is going 1 or 2 stages lean to see if that helps. then the oil change.

Thanks again!

Re: Leaking Oil Filler Cap
 

I guess you missed a couple things in that ‘plug and play’ hype.
Can’tblame You, everybody does.
No such thing on an eddy carb.
You need two things to make them work.
A fuel regulator set at 5psi. Eddy carbs are finicky. Don’t like more pressure than that.
And a heat spacer under the carb. Gotta keep the fuel in the bowl relatively cool.

Re: Leaking Oil Filler Cap
 

"Plug and Play" probably works 10% of the time. With a mild E-Brock cam, Performer intake and 600 CFM E-brock carb on a 305, I had to enrich the mixture to get it running right. Just buy the whole needle and jet kit. You'll probably only use one set of springs, rod and jets, but if you feel brave, you can practice tuning it. The metering rods and springs can be removed without taking the carb all the way apart, which is a nice feature.