2.0 Crank & Head Venting Issues |
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2.0 Crank & Head Venting Issues |
tjtryon |
Oct 17 2016, 03:56 PM
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#1
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Newbie Group: Members Posts: 20 Joined: 15-June 16 From: Indianapolis Member No.: 20,112 Region Association: None |
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 |
Oct 20 2016, 10:21 PM
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#2
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Advanced Member Group: Members Posts: 3,886 Joined: 6-September 11 From: St. Petersburg, FL Member No.: 13,527 Region Association: South East States |
(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 |
Oct 21 2016, 06:03 AM
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#3
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Advanced Member Group: Members Posts: 2,311 Joined: 22-February 13 From: Middletown CT Member No.: 15,565 Region Association: North East States |
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 |
HAM Inc |
Oct 21 2016, 06:44 AM
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#4
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Senior Member Group: Members Posts: 846 Joined: 24-July 06 From: Watkinsville,GA Member No.: 6,499 Region Association: None |
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. This is correct. 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. The problem with this approach on wet sump engines is that during spirited driving the added oil residing in the heads leads to a lower level of oil in the sump area, and reduced oil pressure. We have had many customers that blocked off their vents and solved persistant low oil pressure problems and reported lower oil temps. 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 appears to not be so much of a problem on nonvented heads. When heads vents are in place the pressure pulses move air (and oil) in and out of the head vents. When the vents are closed pressure pulses, but air is not moving through the cavity to the atmosphere, hence pressure changes, but no air flow. The aeration in from the valve train is a fraction of what is experienced from windage in the crankcase. This may be a case of "six of one, half dozen of another". [i]On docile street cars it is. But on wet sump engines that see track time or AX or spirited mountain driving, etc. oil parking in the heads robs oil from the sump. Most people with vented heads are accustomed to adding an extra quart or so before tracking or AX'ing for this very reason. 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. Like I said before, we have had many customers who solved low O.P. in corners by simply blocking their head vents. The track is when it's most likely to be a problem. On a dry sump engine the crankcase [i]should be vented through the sump tank anyway, so that's another matter entirely. The engine can puke all it wants and it goes right back to the sump tank. On a wet sump engine that pukes oil into a can, even if the breather can has a fancy drain (which is just another path to the atmosphere when the puking is going on) the oil that's pumped to the heads through the pushrods and sloshed out of the sump area through the pushrod tubes takes a very long path through hoses, into the breather can, (where it sits till the puking stops) before it finally gets to drain back to the sump. Doesn't make sense when you think about it. [/i] 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?) Never did this, but if it is higher than the sump pressure it will aid in moving oil back to the sump, which is a good thing. The more time the oil spends in the heads, the higher the oil temps. 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 |
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