z ya Posted March 18, 2003 Share Posted March 18, 2003 After fighting my leaking maifold over and over Quicker240 brought up a good point about High crankcase pressure possibly being the culprit . Whats is the best method for relieving this excessive pressure? Should I go down to the local Kragen and get a PCV valve? If I do should I use a breather on the other side? Or should I go with Moroso set up that sucks it out of the exhaust?? When I had the k/n style breathers awhile back I remember oil coming out of them and leaking on the valve covers. I figure that is a sure sign of High crank case pressure. Or can I just use some breathers with the nipples on the end and run them to my air cleaner. Thanks Quote Link to comment Share on other sites More sharing options...
Guest BigWhyteDude Posted March 18, 2003 Share Posted March 18, 2003 check your pcv systm and make sur that it is working correctly. A good way to do this is put s piese of paper over your oil filler hole with the motor running its should have enough vacuumm after a shot time to hold the paper against the valve cover. if it does not do this check the pcv valve. whens the last time you changed it?? Quote Link to comment Share on other sites More sharing options...
z ya Posted March 18, 2003 Author Share Posted March 18, 2003 Thats the thing I have never ran a PCV valve before. All I have used are dual breathers. My question is should I use the PCV or dual breathers to get rid of max crank case pressure??? And if I use the PCV should I use a breather on the other side??? Quote Link to comment Share on other sites More sharing options...
grumpyvette Posted March 18, 2003 Share Posted March 18, 2003 what would be "BEST" is to re-ring the engine to reduce the loss of CYLINDER PRESSURE GETTING PAST THE RINGS!!!! if DUAL breathers can,t keep up with the crankcase pressure somethings very WRONG!! Quote Link to comment Share on other sites More sharing options...
Guest greimann Posted March 18, 2003 Share Posted March 18, 2003 A PCV Valve is more or less a check valve that allows gasses to flow out of the valve cover and crank case, but not the reverse. It is actually a restriction to the flow if you were to try and blow through one. The main purpose is to capture combustion blow by to keep it from venting into the atmosphere. The amount of flow in this system is not enough to draw a negative pressure. If you have breathers on one or both valve covers, that should be sufficient to vent any positive pressure you may be building, even if your ring seal is as sloppy as a $4 prostitute. Also, plumbing in a PCV to a setup that doesn't have one now will require major re-tuning of the idle circuit because you will have introduced an air bleed into a previously closed system. All that said, I dont' think that crankcase pressure is the problem. There is something else going on, like perhaps porosity in the manifold or block castings, severe mismatch of the manifold and head geometry due to machining of the heads and block, missing distributor gasket, or something else that is very difficult to diagnose without actually putting some eyeballs on the problem. Quote Link to comment Share on other sites More sharing options...
jt1 Posted March 18, 2003 Share Posted March 18, 2003 Can you put a gauge on it somehow and see how much pressure it's building? That would determine whether it's a pressure problem or casting mismatch. Question would then be how much is too much? I don't know, but would guess over 2-3 psi is excessive. John Quote Link to comment Share on other sites More sharing options...
Guest greimann Posted March 18, 2003 Share Posted March 18, 2003 Here is a possible source of a hidden oil leak! There is a counter bored oil plug under the left cylinder head, near the area where the oil gauge sender screws into. If this plug was omitted during the rebuild, it would leak oil for sure. It is hidden unless you remove the left head. It is an easy thing to miss during a rebuild. Here is a diagram of what I am talking about. Note that the diagram is a view from the front of the block, but shows the hidden oil gallery and block plug (in yellow) at the rear of the block. Quote Link to comment Share on other sites More sharing options...
Mike C Posted March 18, 2003 Share Posted March 18, 2003 What do you have on it now? I'm with Grumpy on this one... There are no disadvantages to running a PCV on the street IME, and the dual breathers should be sufficient as well, but can be messy as you noted. I would go PCV, which is "positive crankcase ventilation" and it does actually put a negative pressure on the crankcase, or behave actively if you will. Not as significant as a vacuum pump, however. The exhaust evac is only effective at reasonably high exhaust flow rates, not good for the street. I think you have a ring sealing issue, however. Time for a leakdown test, or at minimum a compression check. How fast does your oil get dirty looking? 1000k miles? 2000k? How often do you have to add oil? Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted March 22, 2003 Share Posted March 22, 2003 Just a possibility.......I had severe crankcase pressure (enough to push the dipstick out the tube on a 1/4 mile pass!). After stopping short of full engine teardown we discovered that the head gasket had popped between the cylinder and valley area, not enough to really show much on the compression gauge and not into a water gallery so no oil-water party going on. This was due in my case to too much head milling and too much NOS! A set of Merlin heads later and all is well, but it was VERY hard to track the leak down..... Quote Link to comment Share on other sites More sharing options...
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