Cranckcase Pressure Help
Cranckcase Pressure Help I need help here guys. Been having a problem on my FI build. I had a long block built by W2W, (370ci iron, dart heads) During the initial break-in I noticed that my oil had a strong smell of exhaust? Any ideas?
When I started trying to tune the car for boost I noticed that the dipstick had popped out of the tube about 3/8 of an inch. I am running a -10an line from each valve cover to a vented catch can. After more run time and more boost I ran into another problem, It seems as though my crankcase pressure under boost is stopping the oil from returning to the pan. This is an STS system with the scavenge pump for oil return. My oil pump alarm is sounding at around 3 psi of boost. I just don't think the pump can overcome the crankcase pressure. After experiencing this I decided to do a compression check but all cylinders were around 150. During all this I was looking over my build sheets and noticed a math error on the balance sheet. W2W offered to make the balance right and check everything else out(for a small fee). When the motor was returned I was told that nothing was found that could be causing the problems I was describing. Now, after reinstalling the motor I am having the same exact problem as before. Is it possible that something could be wrong with the heads that could cause this? I have approx. 300 miles on the motor and have not noticed any oil consumption. Sorry for the long post, but this is really frustrating. Please, any help/input is appreciated.
When I started trying to tune the car for boost I noticed that the dipstick had popped out of the tube about 3/8 of an inch. I am running a -10an line from each valve cover to a vented catch can. After more run time and more boost I ran into another problem, It seems as though my crankcase pressure under boost is stopping the oil from returning to the pan. This is an STS system with the scavenge pump for oil return. My oil pump alarm is sounding at around 3 psi of boost. I just don't think the pump can overcome the crankcase pressure. After experiencing this I decided to do a compression check but all cylinders were around 150. During all this I was looking over my build sheets and noticed a math error on the balance sheet. W2W offered to make the balance right and check everything else out(for a small fee). When the motor was returned I was told that nothing was found that could be causing the problems I was describing. Now, after reinstalling the motor I am having the same exact problem as before. Is it possible that something could be wrong with the heads that could cause this? I have approx. 300 miles on the motor and have not noticed any oil consumption. Sorry for the long post, but this is really frustrating. Please, any help/input is appreciated.
6 & 8 Second Club
Joined: Aug 2006
Posts: 2,284
Likes: 0
From: Illinois, RT 66 dragway area
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I was helping an alcohol Pro-Mod many years ago, they had the same problem. The hacks that they were 1st tried to duct tape the dip stick. One race it went thru the hood. So instead of finding out what was wrong, they pulled the tube and tapped the hole for a screw in plug.
I myself am a huge fan of vacuum pumps to keep the windage and oil draining properly. Especially with blowers & turbo's. I also prefer leak down test instead of compression. What we do is seal the motor, pull vacuum from the motor with a pump. Solves less windage for the crank to spin thru and helps oil drain faster, or so they say. Some guys prefer the adjustable vacuum regulator. Obviously you need to try something, what you have is not working. I believe for ~$1000 you can get a pump, can and lines. Good luck.
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I was helping an alcohol Pro-Mod many years ago, they had the same problem. The hacks that they were 1st tried to duct tape the dip stick. One race it went thru the hood. So instead of finding out what was wrong, they pulled the tube and tapped the hole for a screw in plug.
I myself am a huge fan of vacuum pumps to keep the windage and oil draining properly. Especially with blowers & turbo's. I also prefer leak down test instead of compression. What we do is seal the motor, pull vacuum from the motor with a pump. Solves less windage for the crank to spin thru and helps oil drain faster, or so they say. Some guys prefer the adjustable vacuum regulator. Obviously you need to try something, what you have is not working. I believe for ~$1000 you can get a pump, can and lines. Good luck.
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As dragster mentioned a static leakdown test is a far better method to see if you have some blowby. I had a similar situation with an N/A engine (blowing the dipstick occasionally at WOT) and it turned out a ring land was broken (causing excessive blowby in that one hole) and what helped me pinpoint the problem was a leak down test I did after having numerous issues keeping the dipstick in the engine.
Somehow cylinder pressure is obviously getting into the crankcase (assuming you have it properly vented). Also, a vacuum pump is a good thing when you have normal type's of crankcase pressures but installing one on an engine with excessive pressure is just a bandaid allowing the real problem to potentially get worse. And there is no guarantee a vacuum pump would even solve your problem but it may help.
I would start checking how well all eight holes seal up with a good dual guage leak down tester. You may find nothing but its the first thing to check before scratching your head looking for other potential causes. And I doubt the pressure would stop the return of oil because the presure would be in every direction.
Hopefully its just something you overlooked routing you lines or some other simple solution....those are nice to find from time to time.
Good luck....keep us posted.
Tony
Somehow cylinder pressure is obviously getting into the crankcase (assuming you have it properly vented). Also, a vacuum pump is a good thing when you have normal type's of crankcase pressures but installing one on an engine with excessive pressure is just a bandaid allowing the real problem to potentially get worse. And there is no guarantee a vacuum pump would even solve your problem but it may help.
I would start checking how well all eight holes seal up with a good dual guage leak down tester. You may find nothing but its the first thing to check before scratching your head looking for other potential causes. And I doubt the pressure would stop the return of oil because the presure would be in every direction.
Hopefully its just something you overlooked routing you lines or some other simple solution....those are nice to find from time to time.
Good luck....keep us posted.
Tony
Last edited by Tony Mamo @ AFR; May 6, 2007 at 11:01 PM.
TECH Apprentice
Joined: Jan 2002
Posts: 320
Likes: 5
From: Nottingham, Notts, England, UK
I can't comment on your pump set up but would guess that you have ring blowby which is normal if you haven'r bedded them in properly. If the rings had sealed you wouldn't have a crankcase pressure issue? Your oil probably smells of petrol as you are experiencing bore wash when hitting boost. Is the sump level rising?
I'd lay off the boost, fill up with mineral oil and give the engine some short hard throttle bursts without boost. Try to get the rings bedded in. Can you run with a pcv circuit or is this a race car?
Boosted.
I'd lay off the boost, fill up with mineral oil and give the engine some short hard throttle bursts without boost. Try to get the rings bedded in. Can you run with a pcv circuit or is this a race car?
Boosted.
the vent you say sounds good provided the catch can is not clogged
i have one 3/8 hose going to before the turbo and one hose going to the intake w/ separator between
lastly i have a pressure large relief on the valvecover
i have one 3/8 hose going to before the turbo and one hose going to the intake w/ separator between
lastly i have a pressure large relief on the valvecover
Thanks for the input guys and I think I might have figured out what is going on. I put a pressure gauge on my valvecover and only saw about 1psi. Is that too much? As I told you guys, my oil pump alarm was sounding, I now think that is happening because of the increased oil pressure that I have now with an aftermarket oil pump. I've read that a restrictor in the oil line might be the fix. Think I,m going to try that and hopefully continue to turn up the boost. Thanks again, and if you think I'm on the wrong track let me know.
