:confused: I am changing My intake manifold from a single plane to an Edelbrock RPM Air Gap dual plane to get more low end on the street. My question is, is it best to use the rubber end seals or to use RTV to seal the ends of the manifold to the block. The current intake has the rubber seals and has been prone to leaks. This is my first Big Block (396,.030 over,QFT 750 Double Pumper Carb, Comp Cams 292 Magnum Cam, Roller Rockers, Full length Headers, Etc.) On all my small blocks in the past I have ditched the rubber seals and used RTV with good results, but I don't know if this is common practice with the big blocks. Any help would be appreciated

RTV everytime.

I used the black rtv on the same intake on a big block and no leaks

Thank's, That's what I was hoping to here, I'll use the ultra black RTV That I bought with the intake.

If you're able...run a heavy bead of RTV on both "china walls" and let it setup over night. Less chance for a leak later on if the RTV is able to skin over before assembly.

If you're able...run a heavy bead of RTV on both "china walls" and let it setup over night. Less chance for a leak later on if the RTV is able to skin over before before assembly.


Do you run that around the water ports as well?

The most important advice is preparation. Make sure that the surfaces are completely clean and flat. After removing all traces of the old gasket material and rtv, I always use a large file over all of the surfaces of the block and intake. I also use a scotch-brite disc on a 90 degree grinder, and resurface the gasket areas. Then wipe all surfaces down with a shop towel sprayed with brake parts cleaner or laquer thinner. I don't agree with letting the RTV set overnight. I run a 1/4" bead on the front & rear of the block and spread it evenly with my finger, making sure that it stays atleast 3/16" thick, and be a little liberal in the 4 corners at the seams where the front & rear of the intake contact the block & heads. Spread a thin film around the water jackets on the heads 1st, lay your gaskets on and spread a light film on top of the gaskets around the water jackets only. I always use lock-tite on my intake bolts also, mainly because the gaskets are so thick, they will shrink as the engine heats up a few times. Always torque your bolts correctly to specs and in order as the shop manual suggests. You will usually have to go back over the torque sequence 3 or 4 times. PS: The reason I don't agree with allowing the RTV to set too long is because it will be dry, you want it to bond to both surfaces. I work on transmissions for a living, and several of them only use RTV for pan gaskets, especially front wheel drive Chryslers, and when we service them, we clean everything up and prep the surfaces, spread the RTV on, tighten the pan, and put fluid in them immediately, never letting the RTV set-up at all, and they never leak.

I use Ultra blue/black RTV. BigBocks66SS' method works for me.

The most important advice is preparation. Make sure that the surfaces are completely clean and flat. After removing all traces of the old gasket material and rtv, I always use a large file over all of the surfaces of the block and intake. I also use a scotch-brite disc on a 90 degree grinder, and resurface the gasket areas. Then wipe all surfaces down with a shop towel sprayed with brake parts cleaner or laquer thinner. I don't agree with letting the RTV set overnight. I run a 1/4" bead on the front & rear of the block and spread it evenly with my finger, making sure that it stays atleast 3/16" thick, and be a little liberal in the 4 corners at the seams where the front & rear of the intake contact the block & heads. Spread a thin film around the water jackets on the heads 1st, lay your gaskets on and spread a light film on top of the gaskets around the water jackets only. I always use lock-tite on my intake bolts also, mainly because the gaskets are so thick, they will shrink as the engine heats up a few times. Always torque your bolts correctly to specs and in order as the shop manual suggests. You will usually have to go back over the torque sequence 3 or 4 times. PS: The reason I don't agree with allowing the RTV to set too long is because it will be dry, you want it to bond to both surfaces. I work on transmissions for a living, and several of them only use RTV for pan gaskets, especially front wheel drive Chryslers, and when we service them, we clean everything up and prep the surfaces, spread the RTV on, tighten the pan, and put fluid in them immediately, never letting the RTV set-up at all, and they never leak.

Thanks for the reply. I did it the first one yesterday and it leaked water very badly. I even had a little on the top of the block after removing the intake. It only ran for about 3 seconds before I saw the leak and it still made a mess. Very detailed, I apprecite it :)

Greg, I am in the process of building almost the exact same setup. Please let us know how she runs. Thanks.

Jason