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Oil in PCV valve

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I decided to recheck the pressure in the rocker cover using the equivalent of the rubber glove procedure. Even with the PCV vacuum connected I've got a very strong positive pressure in the rocker cover- when I checked weeks ago that was not the case- the pressure seemed almost neutral.

When I compare the pressure from the rocker cover vent with the crankcase vent either with both open to atmosphere, or with one blocked and the other open I get a stronger outflow from the rocker cover vent than from the crankcase.

No doubt this is exacerbating the rear oil seal leak, but why a higher pressure at the top than at the bottom? The engine is new, with 500 miles, good compression, no smoking and clean plugs. I have not been using break-in oil. If this is blow-by until the rings bed why isn't the crankcase vent seeing as strong a pressure as the rocker cover, unless the trap is partially blocked.

Not sure where to start. No way the PCV suction could keep up with the outflow that I feel. I would appreciate any thoughts.
 
lbcfan said:
but why a higher pressure at the top than at the bottom? The engine is new, with 500 miles, good compression, no smoking and clean plugs. I have not been using break-in oil. If this is blow-by until the rings bed why isn't the crankcase vent seeing as strong a pressure as the rocker cover, unless the trap is partially blocked.
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I'd like to know this too. Interesting. Presuming your rings have bedded in (and I would have thought so by now) and the main oil pressure isn't high... odd. Has it been steadily high or did this suddenly appear?
 
I've only checked twice. The first time I checked was due to a bad leak from the Moss rear seal on a rebuilt engine. I taped a baggie on the rocker vent when I had the crankcase vented to the carbuerator intake filter housing, and the pressure seemed neutral to slightly negative. Don't know why I went back to check again, but now strongly positive.

My aluminum rocker cover has 2 vents- a large vent fitted by the rebuilder and the typical 1/2" vent that could connect to the air filter housing on a 948. I temporarily capped the large vent, so comparing the 1/2" crankcase vent to the 1/2" rocker vent by touch was easy.

The engine runs great- the 1275 in the bugeye is amazing, but I continue to loose a lot of oil from the rear oil seal. Also, the driver's side of the block is wet with oil, but only below the head- I have't figured out the source, but it's not the rocker cover. Probably the timing chain cover gasket.

I'll try to explore a little more next weekend. I guess I can check the blow-by by adding a little oil to the cylinders to see if it raises the compression.
 
lbcfan said:
Also, the driver's side of the block is wet with oil, but only below the head- I have't figured out the source, but it's not the rocker cover. Probably the timing chain cover gasket.
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Is the head and/or gasket OK?
 
Seems ok. I re-torqued the bolts a couple of weeks ago. All were to spec. Can you leak oil between the head and the block?
 
Yes! I've seen it a few times.

I had someone's '72 Midget here last year that would weep at the left front corner. I finally got it to stop by using some ARP fasteners and going to about 55 lbs torque. I don't think I'd try that with conventional studs though. That was the head I have previously mentioned that would distort when hot and lose the seal between #2 and #3. Once it was milled hot, it may have cured it as well, but I have not seen it since that was done, so I'm not certain.

Sometimes, it's just the head gasket weeping.
 
lbcfan said:
Seems ok. I re-torqued the bolts a couple of weeks ago. All were to spec. Can you leak oil between the head and the block?
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I've seen it too (as Gerard has).
 
lbcfan said:
ok. I'll add it to the list... I guess I bought a kit rather than a finished engine.
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Partly true for me as well.
 
lbcfan said:
ok. I'll add it to the list... I guess I bought a kit rather than a finished engine.

Thanks.
Click to expand...

The "best" Payen gasket is supposed to be the black composite one, but that was the one I used that I mentioned would weep. I have used the different compositions, but always buy Payen. Only had one bad one that had a manufacturing defect and had to be replaced.

Some people like to use the copper spray, but don't use it on the black one.
 
Nasty old trick that I probably shouldn't mention here is to strip a small copper wire out of an electric cord and make up a ring of that to go around the offending leak. I stopped a weeping leak from a casting flaw on a B series engine that way. Got the suggestion from an old mechanic.

Kurt.
 
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