Could it be excessive crank case pressure?
Thread Starter
Instructor
Joined: Jun 2004
Posts: 162
Likes: 1
From: Johnsburg IL
Could it be excessive crank case pressure?
I am having challenges stopping oil leaks in my 383. I have changed the pan casket twice and oil is also leaking from fuel pump plate and balancer seal as well. Parts are installed correctly.
Oil pressure is 35 at idle and 70 at 2000 RPM which is high but I have a HV pump. Compression test was perfect with all between 180 and 188. Two plugs were slightly gummed-up but could be from break-in and adjustments.
Could excessive crank case pressure be the issue and cause the persistent leaks? If so, how do you measure the pressure and what could be the cuase (s)?
Thanks to all for any suggestions / comments
Oil pressure is 35 at idle and 70 at 2000 RPM which is high but I have a HV pump. Compression test was perfect with all between 180 and 188. Two plugs were slightly gummed-up but could be from break-in and adjustments.
Could excessive crank case pressure be the issue and cause the persistent leaks? If so, how do you measure the pressure and what could be the cuase (s)?
Thanks to all for any suggestions / comments
Team Owner
Joined: Feb 2005
Posts: 32,519
Likes: 1
From: central America
St. Jude Donor '08-'09
What are you using for crankcase ventilation? Are you using the standard PCV valve on the driver's side, and a breather hose on the passenger side? I'm wondering if breathers on both sides would solve the problem.
trw
trw
Thread Starter
Instructor
Joined: Jun 2004
Posts: 162
Likes: 1
From: Johnsburg IL
The PVC is installed correctly. Does anyone know how to measure crank case pressure?
My brother said with compression good it could possibly be created by valve stems but the heads were done by a very good shop including new guides.
Any suggestions on what cause of high pressure and how to measure appreciated!!
Thanks
My brother said with compression good it could possibly be created by valve stems but the heads were done by a very good shop including new guides.
Any suggestions on what cause of high pressure and how to measure appreciated!!
Thanks
Le Mans Master
Joined: Mar 2004
Posts: 7,502
Likes: 1,510
From: Little Rock AR
Does it "puff" smoke out of the hole on the breather side if you pull the breather out? If so you may be having more blow-by gasses than the PCV can pull out. Put your hand over the hole and see if a vacuum develops. You want it to pull a vacuum.
If your PCV valve does not rattle when shaken, it could be plugged with crud. You can feel if it pulls a vacuum when you pull it out of the valve cover and put your finger on the hole with the engine running. It should snap your finger tip up if it is working right.
Bottom line is you need to maintain a negative pressure inside the engine crank case to prevent the oil from being blown out the gaskets/seals. The oil pressure does not have anything to do with it.
-Mark.
If your PCV valve does not rattle when shaken, it could be plugged with crud. You can feel if it pulls a vacuum when you pull it out of the valve cover and put your finger on the hole with the engine running. It should snap your finger tip up if it is working right.
Bottom line is you need to maintain a negative pressure inside the engine crank case to prevent the oil from being blown out the gaskets/seals. The oil pressure does not have anything to do with it.
-Mark.
Thread Starter
Instructor
Joined: Jun 2004
Posts: 162
Likes: 1
From: Johnsburg IL
Mark,
Appreciate the info. The PVC valve vac is strong and the breather side builds vac after a couple of seconds but nothing compared to the PVC. This tested with engine cold, does that matter?
I have seen what looks like mist come out of the breather side when the engine is hot. What would cause the blow by? I am not sure how to test if the valve stems could be the issue. Could a couple bad guides be the problem? Engine probably has 200 miles but with oil leaks it is hard to drive without throwing oil all over.
Thanks!
Appreciate the info. The PVC valve vac is strong and the breather side builds vac after a couple of seconds but nothing compared to the PVC. This tested with engine cold, does that matter?
I have seen what looks like mist come out of the breather side when the engine is hot. What would cause the blow by? I am not sure how to test if the valve stems could be the issue. Could a couple bad guides be the problem? Engine probably has 200 miles but with oil leaks it is hard to drive without throwing oil all over.
Thanks!
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Pro
Joined: Aug 2005
Posts: 613
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From: West Central Florida
Several things can cause this. If you have paint on the gasket surfaces it can and usually does leak cause the paint is flexible, not flat and porous. Also, if there is any grease or oil on the gasket seal surface before assembly it wont allow the gasket to stick to the surface and seal. The crank sealing surface may need to be polished and may have scratches or flat spots on it, needs to be smooth and round to seal. The fuel pump could be just a damage gasket due to the pump arm on installation, before mounting the pump, turn the engine till the pump actuating rod is in the up position so the pump can be held up to the block flat by hand, then put the gasket and pump on the engine. The tric to sealing any gasket is to have the surfaces clean dry and tight but not too tight. Putting a thin coat of sealer on the gasket (both sides ) before installing can usually eliminate any irregularity problems on the surfaces. Even on a frsh engine, these gaskets shouldnt leak due to pressure if the pvc system is working right. It may also be coming from only one place and running down on the other making it look like more than one leak is there.
vic
vic
Melting Slicks
Joined: Oct 2004
Posts: 2,662
Likes: 8
From: Knoxville Tennessee
If the breather vents are working on both valve covers something else is wrong. To build the kind of pressure that would cause seals to leak you would need to have a cracked head or heads leaking pressure from the clyinders into the crankcase. With this much pressure oil would be coming up the dipstick too. The carb pulls a vaccuum on the crankcase to expel those gases built in the crankcase, then sends them thru the carb to be burnt instead of going into the atmosphere the way it used to be with a crankcase vent tube. Also, with that kind of pressure it would probably be going into the radiator too. Take the cap off the rad and start it, when the coolant starts flowing if there are a lot of bubbles coming out of the rad you have a cracked head or heads; or warped heads. The block might even not be flat causing this. So many things could cause excessive pressure but I would bet it is something more simple if the engine has not been overheated.
Bernie
Bernie
Thread Starter
Instructor
Joined: Jun 2004
Posts: 162
Likes: 1
From: Johnsburg IL
Thanks to all for the responses.
I know the surfaces for the fuel pums and pan are good and clean. I failed to mention this will be my third oil pan gasket, the pan and timing cover are new and the leak in the front is what created my concern for blow-by.
With compression from 180 to 188 (dry, no oil added) I thought it would be very unlikely the rings were allowing blow-by.
I will keep all posted.
Thanks
I know the surfaces for the fuel pums and pan are good and clean. I failed to mention this will be my third oil pan gasket, the pan and timing cover are new and the leak in the front is what created my concern for blow-by.
With compression from 180 to 188 (dry, no oil added) I thought it would be very unlikely the rings were allowing blow-by.
I will keep all posted.
Thanks