yet another exhaust manifold query

Hot Rod just did a test of all the manifolds and headers on a 300 HP crate motor and there was a thread posted in the last couple days on FABO. The difference between a stock set of 69 318 manifolds and a set of high dollar 340' was 11 HP (305 vs. 316). I know the 69 318's are a little bit better than the stock 65 273's your car came with and are probably an easy swap with no clearance issues. They used a 2 1/4 pipe off the manifold in the test.

By the way, most of the headers tested had no gain and even a loss on a 300 HP motor. Headers are really going to be a pain on your year car and with no real power advantage it's a waste of headaches.

Do a search for the thread on here, there is a link to the Hot Rod page with all the dyno results and I think you'll agree with what I just wrote.