Sidedraft Manifold Porting

[CDN OpelNut]

As some will know, I recently swapped my 40mm sidedraft for a DCOE45.

I was reminded (thanks Otto) that I'd need to increase the bore on the manifold to match the carb. Got to it today.

I have no idea what the standard method is, or if there is one, so here is what I did.

There is a shot of the Irmscher manifold with the DCOE attached.

I located a piece of paper by installing it between the carb manifold and then using a technique I perfected in grade one, I made an etching of the carb.

I cut it out, flipped it and installed it on the manifold, and then painted the assembly lightly to mark the new opening.

You can see that there was quite a mismatch. I removed the material with a die grinder, keeping it at an angle that was a straight shot to the opening at the head. I ended using a double-cut round file for a lot of this.

This manifold has an internal channel that joins the two runners so I was also able to stick a vacuum in one side while I did the other which kept cuttings to a minimum.

[CDN OpelNut]

And after a couple of hours total work, here is the result. Hopefully this will improve breathing.

-C

[wrench459]

Originally Posted by CDN OpelNut As some will know, I recently swapped my 40mm sidedraft for a DCOE45. I have no idea what the standard method is, or if there is one, so here is what I did.

Prussian blue/machinists blue has been used for years. Today we're using
big fat magic markers to mark the ports.

I've often wondered about how much to cut out of the intake,how and where to blend it in. Got any baseline numbers with the 40's?

[CDN OpelNut]

Originally Posted by wrench459 I've often wondered about how much to cut out of the intake,how and where to blend it in. Got any baseline numbers with the 40's?

Nope Sorry. I'm assuming you mean some flow numbers. I don't have that kind of equipment available.

The path from carb to head is such a straight shot with this intake that I simply increased the bore and then removed any material that looked like it was in the way and smoothed it all out.

Only a drive will tell if there is an improvement.