I found the stock exhaust manifold on my 292 to be extremely restrictive. Even if I'd split it, the restriction at the head would have remained.
So I went with Hedman Hedders and don't regret it at all. They fit pretty well (I needed to do some grinding and shaping to get them to play well with the Offy manifold) and from the sound, they've improved the flow about 400 percent. They also sound great with the cherry bombs on 'em.
The thing that convinced me was when I had a dream one night about cutting the muffler off the truck with my Sawzall. I woke up the next morning and thought, "that's not a bad idea!" So I grabbed the Sawzall and hacked the rear 3 feet off the exhaust, thinking that the muffler had to be in that section. Wrong! No muffler! It was already a straight pipe and I didn't even know it!
That convinced me that the manifold was WAY too restrictive. When I put the headers on and fired it up with no mufflers at all....well, it was a totally different story. It sounded like a real motor...and WWIII going off right under my feet.
So if ya want performance, I don't think you'll get it from the stock manifold, even if you split it. If you want a quiet exhaust...well, that's a different story.
