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Posted by Chriscase on Monday, July 27, 2009 at 08:38:52 :
In Reply to: Smoke from the FH6 valve cover vent pipe question posted by Bob Stopka in Panama City on Monday, July 27, 2009 at 02:25:06 :
I assume that by "valve cover vent pipe" you mean the road draft tube, about 1 1/4" diameter, points down?
The road draft tube is cut slanted on the bottom. That means the air rushing past sucks the vapors from the engine. Replacement air comes in through the oil filler. I hope everybody has a vented filler cap? No vent means sludge build up- if the fume don't get sucked out, they make sludge.
Starting in WWII, they went to a sealed system. The road draft tube was replaced by as smaller diameter tube, plumbed to the intake manifold, with a PCV valve. The fumes get sucked into the intake and burnt. Clean air gets pulled in through the oil filler cap, and/or a tube to the air filter.
In the 60s, it became the first required pollution control device. That is pure smog you see coming out of the road draft tube.
A bit of visible fumes is normal, all engines make blow-by, you just can't see it on a more modern engine. Cheaper and easier to retrofit a proper vent system than re-build an engine. Then, if the system makes excessive blowby, you will see it when the oil filler cap is removed.
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