331 Stroker Excessive Crankcase pressure problem

turbosl2

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Apr 5, 2005
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I recently just built a 331 stroker engine with a D1SC blower for my 94GT. I seem to be having a problem with excessive crankcase pressure coming from my engine. I can hear the oil pan either implode a small amount or get pushed out because when i turn the car off and about 5secs afterward you hear it, plus it will puke a small amount of oil out of the pass side breather filter. Also the car leaks oil from the front and rear crank seals due to the excessive pressure. I not sure if this is from the cam being so radical, some have told me so. I have a flowtech induction custom grind, roughly 610 lift. The car pulls 6-7inch of vacume at idle. It does not have any vacume leaks and does not smoke at all. So far there are about 300 miles and 20 dyno tuning pulls on the car and it runs great except for the oil leaking out of the seals and the pan making noise. Some info is i have tall aftermarket valve covers no baffles with a breather filter open to atmosphere on pass side, no breather on drivers side, new factory PCV valve hooked to upper intake (Trick flow track heat). I am almost positive this is from excessive crankcase pressure because of the pressure pushing or sucking on the oil pan. I think in my opinion that it tends to build more pressure at idle, because sometimes when i whipe of the bottom of car, go for a drive, there will be no oil, but when i idle, it will build pressure and drip from both seals, then i shut it off, i hear the pan and it might puke a small amount of oil out the breather onto my headers. I know that baffles will stop the puking of oil but what can i do about the pressure. This is all done without boosting it, and just normal idleing. Could the engine not be broken in yet, if so i built ALOT of engine and never seen them leak when there not broken in, Plus it has 300miles and i am sure after 20dyno tuning pulls it would be broken in by now.
Thanks for the help
 
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cbarr300

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Jun 6, 2006
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first thing I would do is a leakdown/compression test.

As for the crankcase pressure: what I did was run a supercoupe pcv valve (EV127A part number)

Here is some more information that may be able to help you.

Also, I've heard that you shouldn't run a pcv system and a breather at the same time. IIRC, the pcv system is a closed system and will not function properly if it isn't closed.

good luck
 

turbosl2

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Apr 5, 2005
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compression is good. Car does not smoke and runs perfect, no smoke on the dyno either. I was thinking that it is either from not being broken in, or because the cam is so radical that the pcv system cant evac the crankcase. I was thinking about taking out the whole pcv system and just running breathers on both valve covers. Right now i only have 1 breather on the valve cover, hoping that adding the other one will curve the problem.
I never seen a pressurized crankcase at idle before, but i never had a engine with this radical of a cam. 6inch of vacume is prob not enough to clear it out, i was hoping someone else had this problem on there new engine build. But i know for a fact that the engine is good and fresh, expecially cause on the dyno there is no smoke at WOT or idle.
 

chuck943

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Oct 26, 2002
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I was having the same problem on my sons car and I was going to try an evacuation system but he sold it before I got it done. What I was going to do was have and EGR bung installed in one of the headers close to one of the cylinders and install a one way check valve like the ones that are in the crossover tube in the back of the heads then hook it to breather cap that had a tube hole. This should use the exhaust pulses to remove the crankcase vapors.
 

YEAHLOH95

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i have the same problem with my car and have a similar set up ,but i am running a stock low milage short block , what oil pan do you have , i have a t-style canton , my plan is to add a breather to the drivers side valve cover.
 

turbosl2

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Apr 5, 2005
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The oil pan i have is a Canton 7qt. I am not sure of the style but i know it has dual drain holes on it. I was hoping that adding the breather to the drivers side valve cover would help my problem, but i am not sure. If i were to use the headers EGR port and use the 1 way check valve from the old EGR setup, and plumb that into a breather, do you think that would work. I could also plumb it into the inlet to the supercharger i guess. I know the seals are leaking from excessive crankcase pressure because it does it mostly at idle when ther is low vacume. I am also wondering on some valve covers that have breather baffles. My current ones dont and i am not happy with them anyway. They seem like there too tall because i could never fit my TB and elbo back on without making a spacer plate to extend it out from the valve cover. I measured the height from the lip where the bolts go through (on top) to the top of the cover and it only looked like 3.5 inches. Maybe 3.75 from the surface of the lip to the top. It was very hard to tell. So far it is very cramped and my TB rests right on the valve cover, hardly any room for a drivers side breather, plus the alternators voltage regulator rests right on the cover in front, even after i shaved it down. Does anyone have any recomendations on that, and what else i should try to relieve the crankcase pressure. What about dual PCV valves on each valve cover, and remove all the breathers.

Thanks
 

chuck943

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If i were to use the headers EGR port and use the 1 way check valve from the old EGR setup, and plumb that into a breather, do you think that would work.


That should work,the exhaust pluses from the cylinder close to the port should help pull the crankcase pressure out. I would think this would work better than the PCV system you are talking about.
 

chuck943

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Thats a good thing for brakes not sure if it will help on crankcase pressure,are you thinking of plugging PCV to it? I would wonder if the pump would be able to keep up with both of those items?
 

turbosl2

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Apr 5, 2005
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I am not sure if it would keep up. I know that if i pull vacume at the booster i would think that it would pull vacume at the intake, thus pulling vacume at the PCV valve. I am not sure if it would work or not.
 

turbosl2

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Apr 5, 2005
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that is true. Is it common for the oil to get pushed out of the rear main and front seals with a big cam. I was totaly not expecting to have oil leaks on a fresh motor. Any info on aftermarket valve covers for our years. Not sure why but the ones i have sit flush on the alterantors voltage regulator, even after grinding the cover down a little.

Tom