by riverboater » Thu Nov 02, 2017 1:48 pm
Having played with exhaust parts swapping many times I have been surprised by what I found. On stock engines there is not enough difference to make it worth the money. On stock engines that are bladed to allow 5g rpm you do see some differences from log to centre rise, about 150rpm depending on what log to what centre rise you chose. Now you would think that stepped up cam and cu. in. would tell a much different story, not so much. When playing with a 426 cu. in. SBC, dynode at 502hp at 5200 rpm, blades to allow that 5200 rpm. Now I did not try logs, I did start with Kodiak 3-1/2 inch and jumped up to the NEW BETTER breathing 4 inch Kodiaks, Had to use a photo tach to tell I gained about 38 rpm. Then I had a chance to try water cooled through transom headers, looked SHARPE and really looked fast just sitting still. Didn't make a full 100 rpm over the 3-1/2 Kodiaks. Some time later I stuck a set of automotive dry headers mounted upside down over the transom. Now with no water and the ability to change collector size and length I was able to suck almost 400 rpm over the 3-1/2 Kodiaks. that was almost 20 years ago now and my ears are still wringing. In my opinion there are better manifolds available but not enough for me to spend full retail. Used performance exhaust can be a tricky purchase as hot things crack. you see a bit of thru transom header and centre rise on outlaws web site in the classifieds. The offshore powerboat face book page is full of high end exhaust for sale, but again now you are adding salt water to the used equation.