340 intake gasket....use gasket front & back or silicone?

Installing an Edelbrock Air Gap RPM on my 340 and wondering which is "guaranteed" the best front and rear seal.......the gaskets in the kit or a big bead of silicone. Needless to say I don't want anything popping out!

I personally would use the gaskets and put a little silicone in the corners. The intake isn't that heavy so putting it down straight shouldn't be an issue.

I've use silicone on mine. I tried the cork gaskets but the intake wouldn't fit... probably because of the decked block.

philcollins wrote:I've use silicone on mine. I tried the cork gaskets but the intake wouldn't fit... probably because of the decked block.

I've just been a beliver in " why reinvent the wheel" in using things that the factory used , thinking that they wouldn't use them if they didn't work. On mine the end gaskets fit over tiny dowels so they won't pop out and the ends of the head gaskets fit into the end gaskets as well. I'd think that that combined with a dab of silicone at each corner would be good...as the factory did it. My deck etc hasn't been touched either - just replacing the stock manifold. Thanks!

I've seen examples, where an amateur would use to much silicone and the oil pickup tube became practically blocked, causing low oil pressure.

smoken340 wrote:I've seen examples, where an amateur would use to much silicone and the oil pickup tube became practically blocked, causing low oil pressure.

Yeah I know what you mean. I've seen guys that said the cork gaskets made the intake sit high and not seal, but again, why would the factory use them over and over again if they were wrong??? I appreciate both sides opinions but just wondering. Thanks again! Larry

I have been told to use the gaskets and just to make sure nothing leaks put a small bead of "Right Stuff" or "RTV" or silicon on both sides of the gaskets and do not forget the corners...a small dab is sometimes not enough.
In order of goodness: silicone is good, RTV is better and Right Stuff is best: But they all essentially do the same job.
A 340 has higher compression which demands higher water flow which means " make sure the gaskets do their job. Cork gaskets are no longer the best, I myself use Felpro.

Just remember when those car were new. One yeat later, their engine were leaking from everywhere so i dont think the factory were doing the right thing.

RTV sealent when applied right does a better job, just look a newer engine, almost no gaskets, just O ring and RTV...


My 360 has been built 10 years ago, with RTV on the intake and still no leaks.

I used right stuff on mine. I always noticed that the cork gaskets would seep oil after about a year, so when I redid the intake I only used right stuff and 3 years later no leaks. I even put it on the neck of my intake bolts to stop some seepage there as well. So far so good.

Nothing wrong with silicone when applied properly. Some folks seem to think more is better, but to much can do damage to the engine. If you buy the Felpro gaskets they come with rubber and not cork.

smoken340 wrote:Nothing wrong with silicone when applied properly. Some folks seem to think more is better, but to much can do damage to the engine. If you buy the Felpro gaskets they come with rubber and not cork.

I bought Fel Pro but it has cork end gaskets. Going to go with silicone I think - seems to be the most popular way. I can see where the cork combined with those pins might be a problem getting the manifold to sit down right. Thanks all! Larry

Use silicone if you want but make sure when you put the intake back on that it goes on level, if it does not go on level and even, this increases greatly your chances of having a leak that you do not want. Putting the intake on level is not always a one man job, specially the heavy steel intakes. a buddy can be a big help.

I have never used the gaskets, just silicone. never had an issue.

Not sure if you've done it yet Larry, but don't forget to pull those dowel pins out. The factory intakes were drilled for them but the aluminum ones aren't. The intake will end up not seating down far enough.