gtotto

Hey guys,

I just got my 65 GTO street car back after a long resto/mod project. I am running an GMPP LSX 376 crate motor with a Maggie TVS 2300. The Maggie has a stock sized pulley and I assume is putting out somewhere between 6-8 lbs of boost. The EFI has a base tune in it and I have made my appointment to get a custom tune put in a few weeks. The setup should put out somewhere close to 600 Hp when all is said and done.

After driving the car for about 100 miles I noticed a few oil drops on the ground. I put the car on a lift and saw it to be leaking at the rear of the motor somewhere. Oil was noticeable at both sides of the oil pan and seemed to be leaking somewhere high up on the motor. It also looked as if the leaking oil had blown back to the cross member and rear end. While looking under the hood I noticed my drivers side valve cover vent tube to be capped off and the passengers side vent tube to be uncapped and left open. I did not see any significant oil spray at the open valve cover vent tube. I ran the motor and looked underneath and did not see any noticeable oil leaking down. "Just for fun" I capped off the passenger side valve cover and ran the motor. I then saw a significant amount of oil leaking down at the rear of the motor on both sides. I cannot pinpoint exactly where the leak is coming from because there are many custom wire looms etc running behind the motor at the firewall. I then uncapped both valve covers and ran the engine again. The major oil leak stopped but I cannot yet say if the oil leak stopped all together due to the residual oil.

So here are some questions......
Is is possible my rear main is leaking? My clutch and flywheel appear to be dry (as far as I can tell) and I would think a rear main would cause a bigger mess as the flywheel would spin the oil around.

Is is possible, wherever the leak is, it is being cause by lack of crankcase ventilation? I would think there would NOT be a huge amount of pressure at idle and I would not think temporarily capping off both valve covers at idle would cause a major oil leak.

If it is a pressure issue, would a vented catch can with 3/8-1/2 inch lines to the valve covers be sufficient? I have seen several venting set ups and the more I see, the more confused I am. I have seen guys running vent lines to the intake (maggie) for vacuum but I also have seen guys say that's a bad idea and not necessary.

Sorry for the long post

Thanks in advance. Any input is appreciated

Ken

RabidStreetRacer

iTrader: (1)

I run mine by running a hose from a LS6 valley cover to a oil/air seperator then to my intake manifold "My LS1 is carb'd. Then I have the two rear ports on the valve covers connect at a T, and run to the air filter to draw in clean air for the engine.

Here is a setup without the LS6 valley cover

gtotto

Got it, thank you. The diagram is very helpful. I have Holley valve covers and have only 1 vent tube per VC. Could I skip the fresh air from the TB to the VC or would it be best to get an adapter for the filler cap?

6669camaro

iTrader: (1)

If your motor is an older ls it could be the cam sensor oring leaking. I've seen a few rear main seal leaks that were actually just cam sensor orings leaking. If you put a catch can on it you can either vent it to atmosphere or to the air inlet, just make sure the suction hose on the catch can goes before the blower, any were after the blower will pressurize the engine and cause major seal leaks.

gtotto

The motor is a new (about 3 yrs) crate motor, recently fired.
I guess Ill have to make sure I have sufficient venting before anything else. If my oil leaks then stop, all good. If not, I'll have to pull the trans to get a better look.

RabidStreetRacer

iTrader: (1)

I have recently been doing a ton of research on the PCV systems on the LS engines and adding oil/air separators. The stock LS1 setup is horrible on these engines as most people know, allowing oil soaked mist to go into the intake and reduce the octane rating of the fuel.
Basically your engine creates pressure due to blow by through the piston rings, that pressure enters the crank case and builds up. It has to be released or it can blow out your seals. But venting to atmosphere causes bad smells and allows the engine to build up a milky sludge, this happened to me! The port on the passenger valve cover towards the front of the engine should connect to the intake manifold, that creates vacuum to pull out the pressure build up. You use the front port on the valve cover because when you accelerate the oil with fill up to the rear of the valve cover and will cause excessive oil into your intake at WOT if vacuum is pulled at that rear port into the intake. You should also run a oil/air separator between that connection and the intake to stop any oil mist from going into your throttle body. So that takes care of the vacuum, but you need to allow the engine to pull air from somewhere because the vacuum at idle will be more than the pressure created by the blow by. So the rear ports on the valve covers should be connected and ran to the air intake between the throttle body and air filter. Or if you don't have a second port then a filter can be used to replace the oil filler cap.

gtotto

Thank you...... Why does venting to atmosphere cause the engine build up milky sludge? Wouldn't a catch can tied to the VCs catch any oil/moisture mixture?

rotary1307cc

iTrader: (5)

Lolz at atmosphere causing build up

RabidStreetRacer

iTrader: (1)

Venting to atmosphere means that you are not vacuuming out the moisture caused inside the crank case, you laugh rotary, unhook your PVC system for about a month and look at your oil filler cap.

http://www.aa1car.com/library/pcv.htm
Read PCV problems

rotary1307cc

iTrader: (5)

Lol your right pcv isn't for emissions


Those trucks running for decades with draft tubes for million miles+ are pure tar when you open them durp

RabidStreetRacer

iTrader: (1)

Sorry man but we are talking about LS series engines which generate a lot of blow by.

rotary1307cc

iTrader: (5)

Lolz...

klrgoat

My 408 in vented to atmosphere through -12 to a catch can at the rear of both valve covers since the turbo build. I push 13psi, never had any milky sludge and have never had more than a few ounces in my catch can.

gtotto

Any oil smell from the open catch can?

klrgoat

I've never noticed any smell at all. No oil mist under the hood either, the catch is baffled also.

gtotto

Very good. Thanks!

mkvamso

iTrader: (2)

Nothing here but a few breathers on the valve covers
Haven't had any reason to switch back to a pcv