Gentlemen,
I'm having problems with oil leaks. My car is a LT1 1994 Z28 383 with about 5500 miles on the motor.
The front crankshaft seal has been replaced once but is leaking again and the rear main seal is apparently also leaking and allowing oil onto my Centre Force clutch (now slipping !).
The car is my very occasional daily driver and perhaps has 8 or so track days under it. Never over revved ..no missed shifts.
4 Bolt block
Calles crank
10.6 to 1 CR
1.52 RR
Competition heads, ported and 2.02 int. 1.60 exh valves
Cam. See below.
Forged everything etc.
New oil pump, water pump etc, etc.
Computer programmed by Doug Rippie
Built by a qualified, but no longer around, Trans Am guy.

So do these motors have excessive crankcase pressure ? Before I replace the seals are there any mods to help this problem ? I read the message boards but I never see any referance to any pressure probs.
Perhaps I am just unlucky and the seals have failed ...LOL.

The cam specs as given to me by the engine builder are as follows:
Int dur 289 deg lift at .50 ---380"
Exh dur 304 deg lift at .50 ---383'
112 centre
This gives me .577 and .582 lift ???
I've never seen specs like this on the cam manufacturers spec sheets. Any intelligent comments welcome.

I am obviously not an engineer so keep it simple.
Thanks.

 

The LT1 has a "positive crankcase ventilation", and it is "fail safe", eliminating the possibility of building crankcase pressure.

Filtered, MAF metered air is supplied from a port in the throttle body, in front of the blades. The air travels down a hose from the throttle body to the passenger side valve cover. From there the air is pulled through the crankcase, up under the intake manifold/lifter valley, and pulled out by vacuum through the PCV valve, on the drivers side of the intake manifold. From there a vacuum line connects to the intake plenum, either using a u-bend hose into the side of the intake (93/94) or a line to the front of the intake, under the TB (95-97).

If your PCV valve becomes plugged (unusual) and pressure did start to build up, it would relieve by flowing backwards through the rubber hose between the valve cover and the TB. This will often put some oil droplets into the TB. If you have excessive blowby on the rings, you will see this condition, because the PCV valve can't handle it.

If you have a S/C, you need to alter the PCV system to evacuate the crankcase. If you add a "breather" in place of the line to the valve cover, you introduce a small vacuum leak, but nothing the long term fuel corrections can't handle. If you were to remove and block the line from the TB, without adding a breather, you could block in the crankcase and pull a vacuum in the crankcase on a healthy motor, and build excessive pressure with a worn engine.

Your cam specs sound like "advertised duration".... not at 0.050", but at 0.002 or 0.003". If those were 0.050 numbers you would idle like John Force's cars.

 

What about installing an oil catch can, would that help?

 

Thanks Injuneer,
I am not happy at having to replace the seals at only 5500 miles and was looking for a reason for the leaks and any preventative measures. It seems that other than correct instalation I'll just have to hope it does'nt repeat.
The cam specs ? Any ideas as to what lift etc this spec might relate to ..or what cam it might be ? It was supposed to be a custom grind but as I noted the builder is not available. (There's a lesson there)
Thanks.

 

I have apparently 2 user names (2 computers) I am also Rock_N_Rolla. Sorry for the confusion.