So what are the options on exhaust manifolds on a 67 cutlass supreme 455 4-speed swap? Currently has a 1970 Olds 350 with stock exhaust manifold in it now. Are the W/Z manifolds what I need to use ? Will they bolt up to current dual exhaust pipes or will I need to extend the pipes ? From what I have heard headers seem to be more hassle than they are worth. Unless someone knows of a direct drop in set ? All help is appreciated. Thank you.

 

Headers vs manifolds is your call. Personally if I were going for power, I'd use headers, but I have no problems dealing with the hassles of fitment and gaskets. That's just me, your mileage may vary.

OEM manifolds for a BBO in a 67 A-body were casting numbers 389268 and 389269 W/X manifolds, which are open log and not the best choice for power. 402295/402294 W/Z will fit and since they are internally divided runners will provide a slight benefit in HP. Exhaust pipes may or may not bolt up. Note that 402295 W is a LH manifold and is obviously not the same as 389268 W which is a RH manifold. This is why I use casting numbers and not the letters that everyone else uses.

 

Great info. That’s just what I was looking for. Thank you.

 

Since its not a restoration with correct casting numbers and letters then use the 70-72 442 manifolds. Mr. Pavado says this is W/Z. The 69 Manifolds; one has a flapper valve in the outlet and you'd want to avoid that as they stick. Correct manifolds for 67 were X/Y. They were empty inside. The W/Z had internal flow dividers which added some high rpm power. Reproductions are available and on eBay the prices for used seem to be declining to something reasonable. If you get used have them surfaced as they warp. Olds did not use gaskets but gaskets are avaialble.