I have a 93 with the LT1, 114,000 miles, no mods. I have fixed the intake manifold leak at the rear of the intake twice in one year. The last time I did the repair I installed a valve cover vent in the valve cover instead of the oil fill cap.
The vent causes the car to idle a little ruf but it has kept the gasket maker form blowing out again. Last week I decided to test it and took the vent out and reinstalled the oil fill cap. After about a week of driving the car, I checked the seals and saw oil residue at the rear and front of the intake manifold. It seems as if there is excess pressure building up and blowing out my gasket seals. I have replaced the PVC valve and the EGR valves and dont know what else to do.
Thanks for any help.

Check the PCV INLET tube for blockage. This tube or hose, runs from the opposite valve cover from the PCV valve, to the intake system between the Air filter, and the TB. In the case of the LT1, I think it actually attaches to a nipple on the TB (and is ported to an orfice ahead of the throttle plates).

Under WOT or heavy throttle, you have no vacuum to draw crank case pressure/gasses through the PCV. If pressure rises high enough, excess should simply vent "backward" through the PCV system inlet and dump into the intake ahead of the TB plates, then be ingested and burned.

Still, there must be some significant blow by to have this much excess gas/pressure. Have you done a comression test or a leak down test? Or a Poor man's leak down?

-Tom

Thanks Tom, I will check the PCV inlet tube for blockage. I have not done a compression or leakdown test or poor mans leak down... How do you do this? and what will it tell me?

First make sure that your entire PCV system is operating properly; that all hoses filters and valves are functioning. Simple system, but just check that first.

A compression check and a Leak down test will tell you about your cylinder sealing. The leak down, more accurately than the compression.

The Poor mans' leak down is simply a leak down test, w/out the gauges to tell you the percentage of leakage. First I do a compression test, to see if there are any "weak performers". Then I take my compression tester and remove the valve from the hose. Screw it into a spark plug hole, set they engine to TDC firing on that cylinder, and then apply ~20 lbs of shop air to that cylinder. Listen for leakage at the:
Tail pipe
Throttle body
Radiator cap
Oil fill cap

With your issue, I'd be paying special attention to the oil fill cap as that is from blow by -the same thing that COULD be causing your symptom. Look for more leakage, in the cylinder that compression'ed the lowest.

Hey, Alpine have you ever noticed if your dipstick or pcv valve popped up alittle? Thats a sign of high crankcase pressure.

Would a oil catch can help in this situation?