Last night a friend & I talking about his motor rebuild, he said he needs new headers his are starting to leak. I said go with Stainless Marine, he said they are only good to 600 hp (I laughed) he says the CMI make more power then SM. Lets hear what you guys think about this debate.

Have never heard either of those statements. SM makes a great product. Just not as flashy

stainless Marine makes the highest horsepower rated marine exhaust. And the upside of having the best exhaust is it will not ruin your motor.

I was sold on the SM's when I read about their design strategy- cast a good manifold, then weld on a lightweight water jacket. They can better control and inspect the base manifold this way and that's the important piece. IIRC, the manifold is 3x thicker than the jacket, idea being that any corrosion issues will have you leaking water into the bilge (where it's visible) and not into your exhaust path.

There are a few engineers that actually have a brain.

Thanks?

There's a good comparison chart with a lot of exhausts represented and their dyno performance on an HP500. I posted it in a recent thread.

Edited, had wrong 500 in there.

I get that the manifold type exhaust systems will outperform a tubular header in terms of not leaking.
What I don't understand is how a "log" style short primary length system can outperform a long primary tubular header. Is the scavanging effect that the tuned primary headers offer not an important factor on a relatively large displacement BBC in the rpm range we use them?

I think the KE's perform like a header, but the others fall short. It's the typical performance/headache/cost balance, IMHO.

So, a tubular header does offer a performance advantage over the stainless marine manifolds but, at the cost of reliability?

I think so. Dyno data shows the headers to make more power and this board will have you believe that no header goes without issue.

Dyno chart thread- http://www.offshoreonly.com/forums/g...no-charts.html

Other relevant info- http://www.offshoreonly.com/forums/g...l-failing.html