Just had intake gasket replaced and main seal is showing no signs of a leak. Valve cover gaskets also look fine. Any ideas?

 

Oil pressure sensor is back there. Maybe its that.

 

X2 could be the problem, but get a light and a mirror and look around back their to see .

 

Depends how it was repaired. Not everyone does the intake correctly which is why it leaks in the first place - cause GM did it wrong from the factory. It's a notorious leak. If it's not that, it's possible that some is oozing out the seam between the heads and intake where they meet in the back.

 

I had rear and front engine leaks. 2 leaks @ rear intake manifold. So, I installed a 1/32" groove in the intake and roughed up the rear china wall. Used Permatex Grey and let it set-up for 1 to 2 hours. Installed manifold carefully and slight finger tight torque. After 4 hours did a final torque. No leaks there now.

I have also had rear main seal leaks. The app is a 97ss 383 FI. It got better when I used a Lucas oil stabilizer (very little oil leak). I have since went to an external crank driven VAC pump. No leaks @ all now, and, about 20 more hp. I think rear seals tend to leak when the engine is off, but, I'm guessing. I know, it is dusturbing.

I've also had front oil pan seal leaks also.

Rear main seal housings can be a problem w/ not being installed concentric w/ the crankshaft. I have found the GM rear seal parts to be better than the Felpro due to dual ribs.

Hope this helps you. B.

 

For years I've done something similiar to 5x, I dimple both China Walls and the corresponding areas on the intake with a nail set.

I have a photo showing them on the 388 I was building for my 96 Vette. Let me know if you'd like to see it.

I also have a STICKY posted on LS1LT1 on how I do my engines if you'd like to read my method. There are others that may works as well, but the one I posted works for me.

Hope this helps.

Jake

 

If I ever pull the intake again, I am going to do this.

 

That sounds good!!! I just may use that idea..NIiice