Engine: Leaky intake manifold

[Guest]

Not being a chevy engine guy, this is all new to me...working on my '63 Avanti the previous owner dropped the 305 into, the 305 was tired and for the past several days I have been working to swap out the 305 with a 350 I bought from a guy, locally.

My problem is the intake manifold is oozing coolant where it bolts to the head, on the front driver's side. I used a permatex RTV along with the gaskets, too. I'm afraid if I crank down on the bolts too much I'll either crack the manifold or break a bolt off in the head.

Is my only solution to pull it off, clean it up and try again with new gaskets?
Was thinking about getting fresh grade 8 bolts and goop them up with the RTV when I seat them, before pulling off the manifold and trying again. UGH!

[jclary]

Just a few quick things, since it has been more years than I want to admit since I worked on a SBC. Did you chase the threads with a clean quality tap before installing the bolts? Were the correct bolts used? If there are blind holes the bolts are going into, it is critical that the bolts are not bottoming out in the hole. If so, you can torque them down but still not be holding the manifold tight. Using the correct torque sequence is important. Make sure the mating surfaces are clean, flat, and not pitted. Sorry if I am covering things you have already done, but these are a few things that came to mind.

[Carl Purdy]

Did you check the face of the intake with a straight edge to see if it is flat?

[sweetolbob]

Tom

Sbc's use a pair of manifold gaskets and generally a set of rubber gaskets on the front and back. They are held in place by tabs on the sides and require silicone sealant where the rubber gasket meets the intake gasket. A dab of sealant should be in place when you set the rubber gasket and a further dab on the joint where they join. You can use straight silicone in place of the rubber gaskets but not my choice.

Also be sure the threads are clean and the holes don't have junk in them as John says above. And of course check for straightness. Also be sure the bolt aren't to long. I think about 1 1/4" is about all they will take if not less.

Never torque them beyond the recommended torque which is probably 20 ft lbs. I used grade 5 generally.

This is not a normal place to find a leak so you'll need to take it off to be sure. Just drain the coolant below the manifold and take it off. Any small amount of coolant can be wiped up and won't hurt anything. Get a new set of gaskets, you'll be surprised how inexpensive Fel-Pro is and don't use anything else.

Take it from an old SBC guy, gooping 'em up ain't going to be a permanent repair.

Bob

[Guest]

Thanks so much, Guys!

I guess I knew what the answer was going to be... ugh.