olds exhaust build question

I'm running a 307 Olds in my 30 pickup. I want to build a header to go outside the frame. Hells gates hot rod makes a flange for a big block. He said he can make me one off of a gasket for my 307.

I bought a gasket and it lists the 307 and the 455 for fit. Everywhere I read about the 7A heads it says they are smaller punier ports.

Anyone know if I can use the big block flange.

 

Rogueman, it depends on which 7A head you have. If its the stock one for a 307 from about 85-newer, the ports are indeed tiny and no it wont work. The 1981-84/85 307 had larger ports and the 400/425/455 exh flange would work fine.

There was a 7A head used on the 1971-2-ish 350 (olds folks call them 7a small-a)and the 455 header flange would be fine there as well.

You didnt mention what year the 307 was that you've got, and in this case, it makes a helluva difference.