Thornton design; a direct replacement for an exhaust manifold.
Our headers are polished 304 stainless steel, with a 1/2" thick steel flange, to prevent warping.
 
Please read the details below to ensure this is the correct purchase for you:
 
-Primary tubes are 1 5/8"
-Collector is 3" wide
-Exhaust flange is cut to accept a 2 1/4" or 2 1/2" exhaust.
-Adapter is needed to fit other sizes.
 
These headers will only fit big block Oldsmobiles with 455, 425, & 400 engines from 1965 to 1976. This excludes 1965-1970 B&C's because the steering boxes are rear mounted (towards the fire wall). If you can fit factory exhaust manifolds these headers will fit without any modifications. They fit a factory 4 speed manual transmission with clearence to the Z bar. It also mates up to a standard exhaust head pipe measuring 2 1/4" or 2 1/2". They will easily connect to down pipes for a big block Oldsmobile.
 
Please feel free to contact us with any questions!
Sold as a pair, with gaskets.