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Discussion Starter #1
Heres the scenario:

'67 corvette 327 motor (VENT BLOCK)

vent is good, its a long tube with a K&N on the end.. the valve covers are cast aluminum with no holes in them except the one for the filler cap (no pcv, ive tried to convince they guy to put it on but no go)

it was fine for a long time now when you drive it (its driven fairly hard) quite a bit of oil comes out of the filler.. tried regular filler caps, and a couple different (new and used) vented caps... happens every time.. anyone have a clue? doesnt appear to be THAT much blow-by or anything... thanks

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Mike Reeh
Gold #34
San Diego, CA
 

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Does the valve cover have a baffle on the inside at the opening for the oil cap???
Since you say the car is run "hard" and that aparently their is some blow-by, I think you need a PCV. As you run the motor hard the internal pressures build, the long tube (I am assuming) goes into the intake, not much splash can get up there, but in the valve cover, splash plus pressure equals leak.
 

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I know very little about vented blocks but it seems to me that if your set up worked for a long time and then started to go bad then something must have changed. I would first check the vent tube and make sure it had no obstructions. When you find out what the problem is let us know.
 

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What Mike is describing is the PCV system for '67 although I have never seen one with a filter on the end, they should just hang down under the engine and air passing the end of the tube creates a suction to evacuate the block. There is no EGR system for '67. If oil is coming out of the filler is sure sounds like excessive block pressure due to pressure going by the compression rings. Oil ring may still be doing it's job so no smoke out the tail pipe. Do a compression test and or leakdown test.

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Steve Strasemeier (70SS 396, Fathom Blue/White Stripes)
 

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Mike is this a hi milage motor? There is a baffle in the lifter galley for the vent pipe. If this gets plugged it will allow pressure to build up in the crankcase. Having a filter on the vent pipe may be part of the problem too. It could cause enough restriction to keep the system from operating properly. A pcv can be added to the engine and still keep the same valve covers. In 65 the draft tube went up to the air cleaner and there was an in line pcv valve between the carb and the fill tube on the manifold. I have also seen 67's with an adapter on the draft tube hole with an inline pcv to manifold vacuum and just an breather cap on the fill tube.

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Philip Valentine
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"Perseverance is not a long race; it is many short races one after another."
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