Intake manifold - best way to avoid vacuum leaks

[moparmaniacc]

I currently have a 440 with stock heads and an Offenhauser dual plane intake on my '70 Chally.    Last year I had a local shop send my engine out for a rebuild and then they reinstalled the Offy intake and accessories when it came back. I wanted to go with an Edelbrock while it was apart, but they talked me into reusing the Offy due to "supply chain issues". 

It seems to have an intake manifold leak.  To be honest I think it had an intake leak before I had them do the rebuild.  During the rebuild they switched to a mild roller cam and roller rockers.  Not a radical cam.  But now I only have 7.5" vacuum at idle and the engine speeds up when I smother the carb. I'm pretty sure the leak is through the valley pan near the front of the engine. 

I know I should take it back and make them do it right, but the shop is backed up and I am tempted to do it myself, but of course then that would give them an out.

Anyway, I bought an Edelbrock 7193 Performer and a FelPro1215 valley pan/gasket kit.  I tried finding a good article on here how to do the job right to avoid another intake manifold leak.  I know there's lot of opinions on this.  Skip the paper gaskets, don't skip the gaskets.  Use blue permatex vs install it dry, etc

I will keep looking, but can someone help me out.  Sorry I haven't been on here in awhile, I used to be on Moparts a lot.  Thanks.

[jimynick]

I don't see what the valley pan has to do with the intake if it's a two piece deal. Set the intake on the heads and get the MkI eyeball going to check gaps and uniformity. If the size and angles of the intake/head are reasonably parallel then I'd buy a tube of the expensive Right Stuff and give 'er a go. If they decked the block it can cause a poor angle at the head/intake surface. My 360 had the deck cleaned up and we ended up truing the intake to restore the fit. Just my    good luck

[Chryco Psycho]

I always use the paper gaskets with some ultrablack silicone between the heads & pan where oil can get pulled up but just seal the intake to the pan on top , torque it down from the middle outward .

[Scooter]

Back in the day I had major issues getting the valley pan to seal on my 383 with the stock cast intake. Musta had that thing on/off a half dozen times. Did not have any visual fitment issues or installation issues.. it just would not seal.  Went right on and torqued according to spec.. At the time (30 years ago) the Felpro tin gasket came with the "diamond seal" coating or some similar name that claimed you needed no sealant. Rubbish. IIRC I ended up using RTV on both china rails and around each individual runner to finally get it to seal properly. Never had an issue from that point forward. IMHO as long as you do not make a sloppy mess.. why would you NOT use RTV? There is no downside.

GL!