edski

Just saw these on eBay any thoughts
https://rover.ebay.com/rover/0/0/0?m...2F183352175278

Olds64

It mentions they're being sold by Thorntons. They have a good reputation.

olds 307 and 403

Good reviews, well made, stainless and fit factory or replacement dual exhaust pipes on pre cat cars.

edski

Can I expect better performance over stock manifolds

oldcutlass

Not much, if you want increased performance stick with long tubes.

olds 307 and 403

There will be some improvement, the argument is how much. Our manifolds flow poorly, our Olds V8 take up a lot of space under the hood, so space for better flowing cast iron manifolds was no easy task, so they just capped the regular manifolds, even on the W31. I still say the tests done on a 300 hp Dodge crate motor was a fair comparison. They started with truck/van manifold's, very close to your stock 330 or any typical SBO manifold. I owned a 77 Dodge Van, I blew up the 318 that I swapped in. I bought a car 318 to put in, I had to change one, if not both manifold's and put the shitty log truck/van manifold's on to fit under the dog house. Either way Mopar Muscle did the test, starting with my awful manifolds, then the better car/360 manifolds gained 11 hp, the coveted and expensive 340 hp manifold's 13 hp, shorty headers 20 hp and long tube, stepped headers 28 hp from the base number. All similar torque gains to the hp each one made. Also remember the system down from the manifold or headers will also affect what gains can be made.