well had to reseal the back of my intake manifold about a year ago and now it looks like its leaking again.

i know this is a common problem so im looking for any known solutions. would the rubber or even cork gaskets made for older SBCs work on the LT1 block? ive also heard copper RTV is better since it is made for high temps.

any advice? and no one say make sure the surface is clean and that theres enough silicone.

 

I use either Permatex Ultra black or Copper. Both work well. My only advice is retorque the bolts after about 3 to 5 days of daily heat cycles.
I'm in full belief the reason for this problem is due to the intake bolts loosening up or insuffcient sealant. I do not believe for a second the EGR vent pipe has anything to do with it.

 

Apparently we've been to the same school on this but I'm left wondering why you believe this way. The egr aspirator tube becomes extraordinarily hot compared to the relatively cool intake manifold and understanding the characteristics of aluminum near such a heat source the potential for distortion seems reasonable.

However, the way the manifold is sealed is such a funky thing and it is little wonder they all end up leaking. I just used the black 500 degree rtv that came with my gasket kit and liked the way it flowed and applied.

For NoRiceInside; Perhaps the best thing you can do when you lower the intake on the valley is to use some type of guide in two of the corner bolt holes. I may have used two pencils so the manifold went on without any movement after it made contact.

 

I had same problem. I used a dremmel and small "saw-cut" bit (about 1/16" wide) to hand machine a small grove in the intake manifold @ rear (side to side on the flat. Also, roughed up the block and manifold with emory. Vac up all the particles! Then, I let the RTV set-up for 45 min, or till it is semi-hard. Set the manf. down (the hard part) and, only hand torque. Wait another 30 min. Then final torque. This seamed to solve my leak problem.

 

I use the Permatex Ultra Gray (all the Permatex's are good) and never have leak problems. Also, clean the surfaces with solvent and allow the Permatex to cure-out for about two days before starting the engine and you won't have any problems with leaks.

 

I used Permatex Ultra black, cleaned the surfaces on both the manifold and the block, heads with brake cleaner. I also used thread lock on the bolts and let it sit overnight. Several months later, everything is still dry and tight.
I hate oil leaks, I also dab a bit of ultra black under the valve cover bolt washers. Keeps em clean and oil free.

 

i read somewhere about the block being iron and the manifold being aluminum is what causes the leak. they have different expansion rates, but if you think about it, all gen 1 SBCs are iron blocks with aluminum manifolds...

well as for my problem i think its the retorque that might have caused it. i never do that after the initial torque. also too, i resealed my oil pan last month, and i used a cherry picker to do so. i removed two intake bolts to hook it up, so taking those out could have distorted the manifold...

 

I was at the shop the other day and the mechanic told me that it was because of the egr tube that runs behind it heats up extremly hot and messes up the gasket in the rear. I dont know if he knew what the **** he was talking about. but thats what i was told. I got rid of all that **** on my old car. and the intake still leaked...

 

yeah it cant be the egr. old SBCs have exhaust gas constantly running through it too...they dont leak because of it.

 

i did this three years ago and it's still bone dry felpro gaskets and black rtv. only trick i used was a center punch making about 30 dimples on the block and manifold to hold the rtv. has not leaked a drop since and i never retorked any of the bolts

 

By trial and error. About 7 years ago when I was so intrigued by this I decided to do some testing. It was not well known at the time when this topic was at its peak that people realized the intake manifold bolts could get loose enough to take off with your fingers if not retightened in sequence. After applying new sealant and retorquing the problem did not return. I had a webpage dedicated to this fix to counter Ken Colling's "intake leak fix" to combat some of the cancerous rumors like it being necessary to "sand on the block and intake..." to help the sealant cure. I received e-mails from a few GM mechanics and service managers who all told me most of their findings were an extremely conservative amount of sealant used from the factory. I decided that was one of the problems and the other was not retorquing the bolts after the fix has been done. Lo and behold after I announced my findings on this very forum Ken's webpage added the "retorquing" method.

 

Wow. Haven't heard that name in a while! Brings up memories...Comp T/A and Firehawk covered in Zaino daily, dancing frogs.... Do he and Mary still have the F-Bodies (I forget the exact # of # they were)?

Damn that was a long time ago. I feel old.