Benefit Of A 2 1/4" Exhaust On Hipo 289

I can't speak from experience, but you should gain a little power from enlarging your exhaust. If memory serves, someone somewhere offered exhaust manifolds that were advertised to increase power similar to headers. If you could find them, they might work for you. Or a second option you could do is send your manifolds in somewhere to have them extruded to open the whole manifold instead of just the ends. These are options if you have/want to spend the money. Grinding and enlarging the opening should help a little, just not quite as much. Hope this helps a little.

No problem! I was looking to see if I could find the manifolds that I was talking about, but really wasn't having any luck. I wonder if what I was remembering were probably what you already have. K code manifolds already flow better than average Windsor manifolds, so maybe what I was remembering were reproduction K code manifolds? Anyway, this *could* be a cheaper option if you wanted to keep manifolds instead of going with headers and didn't have K manifolds already? Or if you didn't want to risk damaging some OEM manifolds, you could get some reproduction, or maybe even used 351W manifolds and grind/extrude on them?

(Copied from DIYFord.com...)


The 289 High Performance exhaust manifold looks like an iron shorty header. It also resembles the 351W exhaust manifold. This is a C3OE casting number manifold that may have been cast by an outside supplier. There are no foundry markings on this manifold.