I have a 64 Cutlass with the Olds 403 small block and a Muncie 4spd in it. What headers can I run in this car? Will small block headers for a 68-72 work? Thank you.

 

Thornton has shorty style, out of stock right now. I'd call about your application first.

https://www.thorntonmusclecars.com/p...***-350-engine

 

If you want real headers for performance (as opposed to shorty headers for appearance), ARH is the best bet. There's a reason why they cost so much more. The frame on the 64-67 cars is slightly narrower in the engine bay. Headers for these cars were common years ago, but today the manufacturers really only support the 68-up cars. Every header manufacturer routes tubes differently, and one vendor's 68-77 headers may fit an early car better than another's. Unfortunately there's no good way to know.

 

Holy smokes Joe, 1500 US for the headers.

 

Joe would extrude honing the exhaust manifolds gain any HP?

 

If you start with W/Z manifolds, yes. The W/Z castings have individual runners. Unfortunately they won't work on the OP's 403, and despite what vendors may say, the aftermarket SBO manifolds are NOT W/Z type. They do not have the individual runners.

 

Its a good thing the OP car is not a "supreme". It will not fit

 

The really ludicrous part of that is that Summit has a footnote on they G-body trans crossmembers that they will not fit Supremes!
Talk about common sense being uncommon.

 

How are these headers for ground clearance? Overall fussiness/maintenance?

 

Pretty much the same as for any headers. Yes, they will hang lower than manifolds. Yes, eventually the gaskets will leak and require replacement. Yes, you will probably have to move the combo valve.

 

Thanks!