intake manifold gaskets not holding a seal

okay, i'm gonna try my best to explain this. please bear with me.

first off, let me state that ive recently had a problem with my intake manifold (LT1 intake, btw). i recently pulled the intake manifold off to check out a lifter and found that the intake gaskets on both of my heads were wet with oil on the lower portion of the intake. i had found that the head ports where oil stained on every single port. after i found this, i concluded that i mustve done something wrong on the original install and just went ahead and put on a new set of gaskets. now before putting these gaskets on, i cleaned all the threads of the heads with a thread chaser. after mounting the intake to the block, i place all the bolts in place and then tightened them in sequential order and tightened to specs via instructions from my helms manual. after one heat cycle of 20 or 30 minutes, i went back and rechecked all the torque settings. all bolts were still torqued to the proper torque amount. all was good....

....or so i thought. all that happened about two to three weeks ago. i believed i was having the same problem again after a poor performance at the track last night. i pulled a plug and found it covered in oil (i found this exact same thing the first time and pulled all the plugs and cleaned them). i pulled the intake and the exact same thing has happened. hmm? so i thought about it for a few and called up a friend of mine to ponder the situation with. we've come up with the following idea which we thought the problem could be.

when i had the block rebuilt, i had to have the block zero decked due to some slight warping. so the area around the pistons (where the heads sit) has all been slighty shaved a bit to even the top of the block. so now i assume that the heads sit down slightly lower than that of what they used to. however, the center of the block where the intake sits is untouched (i know for sure that it was untouched). so the intake still wants to sit exactly where it used to. that would make the intake not seal properly on the inside lips where it rests against the heads. hence, why i'm having repeated problems with the intake seal not sealing completely.

now if this is the problem, how in the hell would i fix this? would i have to shave the lower center portion of the intake to let it sit slightly lower. or would i have to pull the block out to have the center piece shaved down a bit (please say no :D )? i doubt that i could use rtv on the gaskets to help maintain a seal. or could i? is there a thicker gasket i can use? any help with this would be appreciated. thanks in advance.

btw-i'm almost positive i could put this problem in the advanced section. however, if you feel otherwise, please let me know. thanks.

Be absolutely sure that the manifold has clearance on each end-rail when it's sitting on the gaskets. You should be able to slide at least a .050 feeler guage under the end of the manifold when the bolts are tightened. Once that question is resolved you may need a thicker intake gasket to compensate for the material removed from the deck. FelPro #1245 requires some minor trimming around the ports and some new bolt holes since it is designed to fit on a traditional small block head. Use the old gasket as a template to determine where to put the new holes and where the ports need to be trimmed. Don't worry about the water passages in the gasket. It seals just fine. The #1245 gaslet is .120 thick and has excellent compression qualities. I avoid using RTV around ports since it reacts poorly to contact with gasoline. Instead, I use a more traditional sealer such as Gasket Cinch to hold the gasket in place while the RTV on the end rails sets up.

I have used this approach on a number of LT1 engines after the blueprinting process compromised the intake sealing surface. No problems with it.

Good luck.

c

I use SCE gaskets...use weatherstrip adhesive around the ports. Never have a problem with gaskets moving.