2.0 Crank & Head Venting Issues Options

[tjtryon]

Car: 1973 2.0 with dual Webbers

Issue: I have a leak from the drivers side valve cover, and poking around, I know my crank & head venting is not correct, which may be what's causing issues. I wanted to fix this first, before I change the valve cover gasket.

I have what I believe is the CB breather box already on the car. It has a hose connected to the oil filler area, one to the fan shroud, and one that is venting to atmosphere.

I have a hose port at the base of the carb intake manifold on both sides, that does seem to vent air out. I assume these are the head or valve cover vents, but am not sure. Additionally, nothing in the system seems to pull vaccuum, unless the fan shroud vent does so.

I have 3 main questions: What are the hose ports at the base of the carb intakes (front of intake on drivers side, rear of intake on passengers side)? What's the correct routing of the hoses? Where does the system pull a vaccuum?

Many thanks in advance!

[ThePaintedMan]

(IMG:style_emoticons/default/popcorn[1].gif)

http://hamheads.com/type4-test.php

This is how I setup my car. Did 10 hours at Sebring and never had an issue with oil coming out of any vents. Thanks Len! (IMG:style_emoticons/default/aktion035.gif)

[GregAmy]

http://hamheads.com/type4-test.php

Thank you, that's quite useful info. I agree with the methodology, concerns, and conclusions, especially in regard to the pressure differentials and its effect on oil drainback (a concern that I share).

So (if I infer correctly) the suggestion here is to, effectively, allow the top end to "pressurize" in order to minimize the pressure differential between top and bottom end, which allows better oil drainback to the case. As a result, however, that add'l pressure can cause valve cover leaks, which is addressed by better gaskets and/or glueing.

On the flip side, the root symptom that led to this testing is collection of oil in the top end which was getting spit out into the overflow container. The alternative "solution" is to collect, condense, and drain this oil back into the bottom end.

I'm not sure I share the concerns about putting this breather oil back into the case; after all, if this is truly "oil that is pumped into the rocker chambers via the pushrods is aerated by combustion gasses" then that also exists with the oil that's being drained back when the vents are blocked.

This may be a case of "six of one, half dozen of another". My personal preference at this time for the race engine is to lean toward allowing the pressure to bleed off, then collecting, condensing, separating, and re-introducing the oil back into the case. However, I now recognize the value of the "block it" position, though I'm concerned leaving any significant pressure in the top end (has anyone stuck an air pressure gauge in there just for funsies?)

For the street, given reduced chance of significant long-term high-RPM use, I'm thinking the "block it" proposal would simplify things a ton, as long as you focus on getting those rocker boxes sealed nice and tight. Oil leaks suck.

Greg