Possible solution to Crankcase Pressure Problem
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Possible solution to Crankcase Pressure Problem
I recently reported installation of an ATI 8# on my 96 SS.
After install, I repoted a lot of crankcase pressure, including popping my dipstick out and spraying oil all about. I feared the worst, which is a possible blown ring land, piston, etc., etc.
After speaking with a gentleman from Combination motorsports, he inquired about my problem, my SC and symptoms. He replied that the ATI instructions to route the PCV hose to the elbow going into the Throttle body was one of two main factors in creating crankcase pressure. THe other was that there is a line between the manifold and the actual crankcase area, routed underneath the throttle body. THe solution is to route both of these to the input (air filter) portion of the blower and close the port on the manifold. If I was to worry about oil splash getting into the impeller, to install a filter can or in-out bottle inline.
Did I miss something on the install. I had this suspicion that the blower was pushing air in from somewhere other than the piston rings.
Does this sound familiar to anyone?
Joe
After install, I repoted a lot of crankcase pressure, including popping my dipstick out and spraying oil all about. I feared the worst, which is a possible blown ring land, piston, etc., etc.
After speaking with a gentleman from Combination motorsports, he inquired about my problem, my SC and symptoms. He replied that the ATI instructions to route the PCV hose to the elbow going into the Throttle body was one of two main factors in creating crankcase pressure. THe other was that there is a line between the manifold and the actual crankcase area, routed underneath the throttle body. THe solution is to route both of these to the input (air filter) portion of the blower and close the port on the manifold. If I was to worry about oil splash getting into the impeller, to install a filter can or in-out bottle inline.
Did I miss something on the install. I had this suspicion that the blower was pushing air in from somewhere other than the piston rings.
Does this sound familiar to anyone?
Joe
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Joined: Feb 2001
Posts: 1,450
From: Belleville, IL
DO NOT run the PCV to the throttle body. Plug the nipple on the side of the throttle body and run a line from the PCV to the intake tract (or to atmosphere). I used a clear tube so I could see how much oil was coming from the PCV. It's a long way from the breather to the intake tract. 
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Joined: Apr 2002
Posts: 908
I had a problem with blowing oil out the rear main on the GN and it turned out to be the PCV valve not closing completely (letting part of 20+psi get into the block!!!). A new one fixed it, although I need a new rear seal. But I'm not sure if the LT1s PCV valve has this closing feature like the GN's do, or if it even has a PCV valve. I don't know. HTH
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Joined: Nov 2001
Posts: 1,751
From: Surrey, BC, Can
Yeah, you had the install wrong for sure.
The instructions I had were to take the PCV valve down to the elbow by the MAF, after the air filter but it has to be BEFORE the blower for sure. Personally i just skipped the PCV all together. It remains in the mainifold but is not connected to anything. Affectively it is just a plug.
Yes, put a brass 5/8 'th (from memory) plug in the hole under the TB. otherwise wou will be venting the boost right there.
I think you may have misread the ATI instructions.
Glad to see you have it fixed.
The instructions I had were to take the PCV valve down to the elbow by the MAF, after the air filter but it has to be BEFORE the blower for sure. Personally i just skipped the PCV all together. It remains in the mainifold but is not connected to anything. Affectively it is just a plug.
Yes, put a brass 5/8 'th (from memory) plug in the hole under the TB. otherwise wou will be venting the boost right there.
I think you may have misread the ATI instructions.
Glad to see you have it fixed.
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Joined: Oct 2001
Posts: 1,462
From: smog zone adjacent to a great lake
Fast Eddie is on the right track. But first, some things to note:
* Better to keep the oem pcv system operational if possible, to accomodate situations when operating off boost. (ie, most of the time)
* Keep pressure in crankcase to below atmospheric if/when possible or at least as low as possible. (that includes NOT adding to the problem with a poorly designed ventilation system)
To achieve the above two points, requires modification to oem pcv system.
The better way to address the above mod is to incorporate a one way check valve in the system to prevent boost pressure from invading crankcase area.
Include in the system, an oil separator/filter to contain oil mist/film from accumulating in the intake air plumbing while operating under boost.
* Better to keep the oem pcv system operational if possible, to accomodate situations when operating off boost. (ie, most of the time)
* Keep pressure in crankcase to below atmospheric if/when possible or at least as low as possible. (that includes NOT adding to the problem with a poorly designed ventilation system)
To achieve the above two points, requires modification to oem pcv system.
The better way to address the above mod is to incorporate a one way check valve in the system to prevent boost pressure from invading crankcase area.
Include in the system, an oil separator/filter to contain oil mist/film from accumulating in the intake air plumbing while operating under boost.
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