Back when I had a cast-iron intake that was filthy dirty and didn't want to seal at the thermostat housing I came across Fel-Pro's reusable thermostat housing gasket:

http://www.federal-mogul.com/cda/content/front/0,2194,2442_7204_7413,00.html

Instead of messing around with sealants, and paper gaskets this thing is installed dry. Just clean off your mating surfaces on your housing and your intake with some brake cleaner and a scrubbing pad like scotch-brite, until it's squeaky clean and dry to the touch. Install this thing, and snug the bolts down by hand (don't torque). This gasket protects a bit from overtightening, but it doesn't have to be all that tight to begin with.

It should seal like a charm. Best part is you can take it off later, clean it off, and re-use it.

I have two of them (one i had to modify when a bolt hole had been retapped in an old intake), but the one I use now I've reinstalled 3 times with no problems.

Does that have a built in o-ring?

Yes, but it's not rubber. It's the same material the 1pc SBC oil pan gasket is made of, so it won't harden, and blow out. It's embedded inside the plastic/fiberglass body the gasket is made of, and looks more like a raised edge than a round O-ring, so when it flattens out after being tightened it will seal flatter than a standard O-ring.

Cobalt,

I have to agree those things are slick.

I had a '74 with an old intake that I just couldn't get to seal. Switched to that, and it sealed like a charm every time.

Brian

You can get them at the GM place too.
They are not Felpro's but they are the same thing.
I might add they work GREAT.

Thanks to Rickf for pointing the following out:

The following message was sent to you via the The 1947 - Present Chevrolet & GMC Truck Message Board Network Contact Us form by rickf.

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I was reading the faq and found the one about sealing a thermostat, whihc is a problem I am currently trying to solve.
(Thread: http://www.67-72chevytrucks.com/vboa...ad.php?t=72077)

The link in the thread no longer works, and the "magic gasket" is not directly named. It took a little while but I finally found on the federal-mogul page the name of the product line. I wanted to add it to the thread but apparantly I am not authorized to update the FAQ, according to the little box of permissions.

The info is this:

The gasket product line is called PermaDryPlus, by Fel-Pro.

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