I have done the dreaded intake seal 4 times on my '94 LT1. I have used Permatex Ultra-Copper, Ultra-Black and Ultra-Grey. The copper I have used twice. I recently blew the head gaskets and had them rebuilt. I also rebuilt or replaced all of the accessories, opti and water pump. I did the intake with Ultra-Black this last time. Sure enough, it leaks again. I am so tired of this leak. The intake mating surface has been checked with a straightedge and feeler gauge. No evidence of warping.

Does anyone know of a high quality intake manifold gasket set that comes with a secondary set of gaskets for the front and rear edge of the intake? Has anyone ever had this much of a problem sealing the rear intake, and if so, successfully used some type of gasket on the front and rear edges? Any input would be great, I want to drive my car.

 

Try a can of The Right Stuff. It's made by permatex and you can get it at autozone for sure. I used Copper RTV and it worked perfectly the first time. You have to make sure and go up the heads a little bit and let it sit for about 5 minutes before putting the intake on so that it doesn't all squeeze out. I also used two studs to line up the intake so that I didn't have to move it around once I sat it down. Also make sure you're using the proper torque sequence.

 

Did you retorque the intake bolts after at least a weeks worth of heat cycles? What size bead are you laying on the block?

 

I have laid a bead about 5/16". I have also tried the Right Stuff. Someone else recommended dimpling the front and rear rails with a punch so the sealant has more of a purchase. What would you recommend between Ultra-Black, Copper, and the Right Stuff?

No know gasket set for the rails?

 

Please do not dimple the block. It is completely unnecessary and will not help your cause one bit. The block surface is porous enough for sealant to adhere to. If it wasn't then why the living hell do I spend at least a half hour scraping sealant off the block and intake?
I've always had good luck with Ultra Copper. I don't know what else to tell you other than to make sure everything is extremely clean by using brake/carb cleaner on all sealant surfaces, thick bead and make sure the intake goes down onto the bead clean w/out having to shift the intake to line up the bolt holes. After a weeks worth of driving, retorque the intake bolts in sequence.

 

Sounds like you're shifting the intake when you're setting it down.

There's no reason ultra black or ultra copper wouldn't seal. I've done countless intakes and none has ever sprung a leak using either.

 

I've had 3 leaks in the rear (97 LT1 intake). Ended up machining a small grove in the rear of the alum manifold (dremmel with small bit). I let the rtv set-up 30+ minutes before assembly. Also, I wait another 30+ minutes before final torque. Have not had any more leaks. I also used brake cleaner on the surfaces to remove all lubricants. So far, I've had luck. I've never had a front leak.