Crankcase Ventilation Help
Thread Starter
Pro
Joined: Mar 2009
Posts: 703
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Crankcase Ventilation Help
Well I blew another intake gasket and now dribbling oil out the front seal.. I just replaced the intake gasket because I was leaking oil out the rear. Both times the engine builder and I used permatex in the front and rear instead of the supplied cork gasket and when I did it, I made sure it was totaly oil free before applying it.. In both cases it didnt start to leak until I did a few rev's.. The front and rear block rail are about 3.5" above the lifter valley so its not like its sumberged in oil so it has to be a crankcase pressure problem (I would assume?). The first time I had a PVC on one side with a good, free flowing breather on the other. This time I Installed 2 breathers and made sure they were not restircted to avoid having the same issue but apparently it didnt work..
Any suggestions?
Any suggestions?
Le Mans Master
Joined: Mar 2001
Posts: 6,640
Likes: 287
From: Ann Arbor Michigan
When you say Permatex, do you mean RTV? You might want to run a leak down test to make sure you don't have excessive blowby for some reason (it happens)
Gary
Gary
Last edited by Duke94; Jun 22, 2009 at 12:14 PM.
Le Mans Master
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From: mount holly NC
2025 c3 ('74-'82) of the Year Finalist - Unmodified
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A leak down test might help you to pinpoint the problem, apply compressed air to each cylinder if you hear air through the carb you have a bad intake valve. If you hear air out the exhaust you have a bad exhaust valve.
In your case you may have a cracked piston ring (or 1 installed upside down) and you will hear air through the valve covers. PG.
In your case you may have a cracked piston ring (or 1 installed upside down) and you will hear air through the valve covers. PG.
Race Director
Joined: May 2006
Posts: 16,528
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From: Dayton, Ohio
Can you tell if the permatex was blown OUT or sucked IN ? Once the permatex is not where its supposed to be it just leaks but if you look close sometimes you can tell which direction it went.
Thread Starter
Pro
Joined: Mar 2009
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Yes, it was the black RTV.. The small block 355 was dynoed (451hp) and didnt leak when it arrived.. The builder said he never really did any quick rev's and basically just did some pulls on the dyno after breaking it in. Both times it didnt leak for me until I did a quick rev off idle (to about 4000rpm).. I'm thinking a quick rev will build up pressure faster as opposed to a slow pull such as on the dyno..
Thread Starter
Pro
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I could see oil being splatterd that high off the lifter valley but to actually blow out another gasket and then start blowing oil out seems a little odd to me.. After it blew the gasket it will now leak even at idle but as soon as I shut the motor down, it wont even spit out another drop. Before applying the RTV, I wiped it all down, wiped it again with thinner and didnt even touch it with my fingers because I didnt want any oil from my hands to cause any issues. I also let it dry for 4 days before firing it back up..
Last edited by Fishndude; Jun 22, 2009 at 12:47 PM.
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Le Mans Master
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From: Butler Pa
Thread Starter
Pro
Joined: Mar 2009
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I think I figured out the cause.
The Edelbrock Elite valve covers have built in baffles under the breather port but the air vents are near the very top (just under the surface of the breather hole).. If you use a long grommet it will extend past the air port in the baffle, which means the air has to vent down and around the bottom of the grommet before coming back up and through the breather. If you use a baffled breather grommet it would be even worse. I think that caused enough restriction to creat some pressure because I just ran the car with no grommets or breathers at all (the baffles in the cover kept the oil from venting out) and it only dripped 2 drops of oil. I still have to change out the intake gasket again
The Edelbrock Elite valve covers have built in baffles under the breather port but the air vents are near the very top (just under the surface of the breather hole).. If you use a long grommet it will extend past the air port in the baffle, which means the air has to vent down and around the bottom of the grommet before coming back up and through the breather. If you use a baffled breather grommet it would be even worse. I think that caused enough restriction to creat some pressure because I just ran the car with no grommets or breathers at all (the baffles in the cover kept the oil from venting out) and it only dripped 2 drops of oil. I still have to change out the intake gasket again
