Water-cooled exhaust manifold for mod motors?

The situation; I bought a Suicidal modded RCMK but while throwing the exhaust system on it the opening of the manifold didn't match the exhaust port as it had been redone. OK, I'm no genius at this stuff but know enough that this can kill performance some. Am I going to have to take a shot at hogging one out with a Dremel to match the port or are there ones already made to let this beast breathe a little better?

You'll never find a flange that matches the port exactly unless it was designed around that certain modded exhaust port.


Just remember, the flow back into the exhaust port needs to be as clean as smooth as the flow OUT.

The ones that I've got I wonder if they could take a modding without hitting where the water is flowing in them. I've done port matching in nitro engines but those are a piece of cake as you're just reworking a flange on a header.
Will, the one you show there appears to be an easier one to work on.

Ron,
RCMK's exit hole is bigger than Zenoahs and while it may seen a daunting task, all you need to is attach manifold to cylinder and using a hook type dentistry pick scratch around perimeter of port shape scratching a line onto manifold. remove it and grind to the line in a belled shape flowing into round area at head pipe mounting.

Hey, I might be able to do that! I've got a set of dental picks that I got from my dental assistant a few years ago and have some Dremel bits that I really haven't used. I thought that trying to use masking tape wouldn't work in transfering a pattern to the different shape with the manifold being already concaved.
Great tip Scott! I knew that I came to the right site to ask this question.

Scott, you've also answered the same problem that I had. I just bought a stock std RCMK side ex Evo motor, but the shop supplied a watercooled flange that is a Zen pattern.
The Evo port is different. We can only get the Zen shape here, not sure if RCMK ones are available anywhere.
I'll also be able to do as you suggest.
David