exhaust manifold question

[Ultrasummer]

So my truck is a 1968 with a 307 in it. I have the ram horn style of exhaust manifolds and I need to address an exhaust leak from one of the exhaust manifolds. I can see where the bolts attach on each side of each port.....but mine also has these funky square bolts on each port. What are these and what is their purpose? These don't seem to go all the way thru and into the block.

[68Gold/white]

They may be pipe plugs. Some engines that year came with what was called a smog pump. It pumped clean air into the exhaust to help burn fuel that had not burned in the combustion process. Many folks did away with that setup, early. It caused problems, needed maintenance, and could be a pain....

[Ultrasummer]

Interesting. So if I bought new ones, I could buy ones without those plugs and all would work just dandy?

[Willys_MB]

Originally Posted by Ultrasummer

Interesting. So if I bought new ones, I could buy ones without those plugs and all would work just dandy?

Definitely. I just did this on my 68 327. I bought the already ceramic coated manifolds that many parts vendors sell.

[Steeveedee]

Originally Posted by Ultrasummer

Interesting. So if I bought new ones, I could buy ones without those plugs and all would work just dandy?

Provided that one of the plugs is the leak. If they have square heads, they are probably 1/4" taper pipe plugs, but the threads in the manifold are for 5/16" B-nuts like one finds on an inverted flare line. If one of those is leaking, just remove it, clean the hole and put in a 5/16" B-nut plug. If the threads in the manifold are toast, use a little JB Weld on the threads. Note that the 5/16" refers to the tubing, not the thread. I forget what the thread actually is atm, but if you go to the parts store, they can sell you that B-nut plug. Common as dirt.