Still fooling around with vacuum troubles on my '56. I'm going to be R and R-ing the intake manifold gaskets and will be installing my precious NOS gaskets, part no. 3742195. If this solves our problem I gotta' do it right the first time. What do you suggest for properly sealing these gaskets?? Thanks for yout tried and true method!!!
-
-
Re: Sealant for Intake Manifold Gaskets
Don, I read your original post about your problem, but there were so many solutions I decided to keep quiet. Now your asking again and I will respond. ---- Just for info, this is a newly rebuilt motor, is it a NEW cam and if so how did you break it in? ASSUMING it was done correctly and no lobes were ruined and ASSUMING the cam and crank timing marks are correct there is little else that will effect the engine in the way you describe, but let me give you some things to look into. Dual point dist. - make absolutely sure the points are set correctly -- ya, ya they're right - make sure!! Timing set at about 12 degrees. Dual quads -- both plugs in the rear of the carbs, both carbs are getting fuel and the idle speed screws are set to make "both" carbs work at idle [I experienced this with a Vette that hadn't been run in years]. As far as the intake gaskets are concerned, older [pre 1970] engines had leaks and we didn't even know as the carbs could be adjusted to make up for the leaks and if you have a leak bad enough to give you this problem, alittle carb cleaner sprayed at the intake/head gasket area would bring the RPMs up. So don't just change them because you THINK this might be the problem. Go through everything again, be methodical, I once rebuilt a 350 and couldn't get it to run right only to find that I had used the wrong scale on the dwell meter. Let me know how you make out. -
Re: Sealant for Intake Manifold Gaskets
I haven't caught up with the previous history of this thread, but I use the following procedure on intake gaskets: Carefully work all mating surfaces on the heads and manifold to make sure there are no burrs or pieces of old gasket material to interfere with sealing, dry-fit the gaskets first to make sure the holes line up and the gasket isn't masking any of the ports or water passages, put a bead of RTV around the water passages on the heads, use a little gasket sealer (I use Edelbrock Gasgacinch)on the head side of the gasket to hold it in correct location when you install it on the head, put a bead of RTV around the water passages on the intake manifold mating surface side of the gasket, use a bead of RTV instead of the cork or rubber seals at the front and rear of the valley (unless you're going for total points by using the seals, in which case you need to locate them precisely and not shift them when you install the manifold), and carefully install the manifold, aligning the holes as you load it. You don't want to shift it to line up the holes after it's in place - this almost guarantees a leak somewhere. Then install the bolts, using a thread sealer (I use ARP thread sealer) and tighten with a torque wrench (25-30 ft-lbs) starting at the center and working out from there in a circular pattern (shown in the Shop Manual). Unless the heads have been milled and the manifold hasn't been milled to match the holes and ports back up, you shouldn't have any leaks. Hope this helps.
JohnComment
Comment