I am overhauling my Uncles 76 model 460. it is in a motorhome. The thing was puking oil out the filler and dipstick BAD. PVC is new and working . Tore it down , the pistons , rings valve guides are all good. Took it to a machine shop, Heads and Block are good. Nobody can see anything wrong.
Only other culprit i can come up with maybe the Muffler/tailpipe is collapsed. I will check that out on my next trip. It is in Mississippi, and i am In TX./ Any help would be welcome

 

Is your filler vented with a filter?

 

Yes i believe it is, but this thing was blowing it out with the filter off the filler off AND the PVC out.. Just to check it.. Blowing out so bad that you could see the oil shooting out the filler..

 

i have never heard of this before
would this happen by overfilling the motor with oil excessivly

 

Sometimes Motor Home & Van engines will shellac the oil return holes in heads closed, like cholesterol in an artery, and shellac
/carbon up vacuum supply take off for PCV at carb base. This can be a catch 22 where one makes other worse so it gets really bad.

All engines add some + pressure to crankcase & if PCV is restricted, removed, or dysfunctional what you decsribe is what happens.

"Henry" says clean oil return holes thoroughly, clean out vacuum gallies in carb base plate, replace hose, PCV Valve & grommet & clean or replace filler cap as it is breather intake to supply air into engine.

FWIW, engine spews oil under acceleration when rockers fill & PCV can't reduce internal pressuring. Failure to repair can cause engine to "woof" rear main & front timing cover crank seals eventually from over pressured internal engine conditions. . .
FBp

 

Thanks for all the replies guys. Got the BEAST rolling again. ONE thing that we didnt notice on tear down, and NOT until I went back. THE intake was burnt out underneath where the exaust passage is(for the heat riser/choke) It was putting so much exaust back into it, the pressure was really bad. Machinist there said that's the first one he had seen in his 30 some odd years of working on them.
Just thought i'd pass that on, maybe help someone down the road.. We live and learn..

 

I also resently had the cross over blow the intake gasket. Gas can get in the oil and destroy the oil, and put some or lots of wear on the motor. depending on how long it was run... I ran for a few hours to get home and put some wear on it. I could hear the lifters creaking and colasping when I shut it off. The oil was so thin it was running out of the lifters and you could hear it and see it when I took off covers. I had the heads off and had the crossovers in the heads filled in at the machine shop. I had the head at intake cut, very light brushing. put a new preformer manifold on and problem solved. the one I had on was crowned 30T in the middle from heat, junk...and the cast one blew out origionally and crowned 20T, junk...other cast intake from spare motor i have, cracked from heat under carb where it hangs down, junk. I hope you checked the manifold for straight at ports. if not it wont last long...also if exaust is restristive or has become restrictive for some reason, age of muffler, colapse ect. problem will not go away...dont wonder to far from home like I did and didnt realize what was up. check cat converter if you have one.. my motor is in econoline. I dont know how long you ran on bad oil if at all but...if so check push rod tips and rockers for wear. If its open mic holes, I would also check chain for slop. try to get an idea about condition, good luck regards Jim