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Discussion Starter #1
I have a Chevy (PCM) 454 with a Mallory YLU624AV. It has been leaking oil at the rear for some time, enough to be annoying but not demand immediate attention. I finally got to it and it looked like the distributor base gasket. I got a few gaskets and some shims and pulled it. It was actually leaking oil out the vents, figured that out when I set it down. Oil is being pushed up past the bushing (and seal?) into the distributor, then leaking out. I read about the possibility of the distributor shaft bottoming on the oil pump so I reinstalled without the base gasket, installed the hold down finger tight, and measured about .010" from intake to distributor base. I'm a Ford guy so this is new to me... The gasket measured .040", shims were .030", .060" and .100". I reinstalled with only doubled up gaskets. A shim and two gaskets seemed excessive. We'll see what it does when I get a few hours on it.

There is no side to side play in the rotor, this distributor is about 4 years old and has 300-400 hours on it. The engine has a PCV off one valve cover and a breather on the other. No other oil leaks and is very clean under the valve covers and intake. This is a PCM 454 in an '89 Supra Saltare, spends nearly all time on the water at 2300-2500 RPM. Thought this was the most relevant forum.

I called MSD (bought Mallory) tech line and they wanted nothing to do with me. Basically said Mallory is inferior junk and it's plain worn out needs rebuild parts if I can find them or replacement. He couldn't tell me if it was just a bushing or a bushing and a seal, couldn't provide an exploded diagram, had no idea how many hours distributors typically last (even MSD distributors) but commented 30+ years is typical. I asked why he would then jump to saying this Mallory YLU was totally worn out when it's only a few years old and shows no appreciable wear at a glance, to which he responded Mallory uses an inferior design and parts. I had nothing against MSD and have used some of their parts in the past, but with how this guy (Tim) acted on the phone I won't be giving MSD any of my money again. IF you buy a company an offer to support their product line for a period of time I expect something more than what I got.

In any event, if anyone has some thoughts on the issue with oil migrating up the shaft of this distributor I'd appreciate some input. This is my first BBC so I don't know all the nuances.
 

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Crank case vented properly? Happened to me once, kept blowing the dipstick...breathers no Bueno.:bangmyhead:
 

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does the dist have grooves for o rings and if yes are the o rings installed?the o rings are not to be used with standard gm blocks.
 

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Discussion Starter #4
Crankcase is vented. PCV on one valve cover and a breather on the other. No issues with oil from dipstick or anywhere else.

It's still getting oil in the distributor after maybe 30+ hours on it the past couple weeks on vacation, double gasket had the expected effect of no change.

What o-rings? There are none on the distributor body to seal to the block and I don't recall any grooves (as a Ford would have). Would be grooves, if present, be in the shaft to seal to the distributor body?
 
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