Getting a cam bigger than the 454/502mag cam is a waste with those heads anyway. The 7.4 has peanut port heads and they won't flow enough to support more than a stock mag cam.

I'm not reusing my stock heads. I already have the exhaust along with aluminum bow tie heads with large oval ports.

Ooops, Just reread and saw that.

I have never heard of anybody modifying the stock 496 exhaust. It s better than the old cast iron stuff, but you will still be choking your engine with it. You will be better off using a set of performance exhaust and will make more power.

Griff, thanks for the replies. To put it frankly, I can't afford a high performace aftermarket exhaust right now. I'm still piecing together the motor. I came accross the 496 manifolds at a third of the cost of hi perf. I'm now worried about reversion as you mentioned so I'm trying to find the most practical way to use what I have to prevent it. That's why I'm inquiring about modifying the stock 496 mani's.

Good luck with the build. I really don't know of any way to modify the 496 riser to dump water farther back. By the time you pay for any fabrication and welding, you will most likely find that its not cost effective.

For now, I would use a mild cam and then when your budget allows, upgrade the exhaust and cam later.