bruceman

This motor is for autocross in class SM2, I am not to concerned about driving on the street. I've bridgeported the end irons and now I'm doing the exhaust ports. I've widened the port until there is half an inch material left on the sides. I"ve ground down 3/8 of an inch on the lower edge of the port to create the round part of a D shape. I've not decided how far to open the top of the port yet but it will be straight with square corners and a well beveled edge.

I was not sure how much material to remove from the bottom so I cut up a scrap rotor housing. I was afraid of getting into the coolant passage.



[attachment=41593:attachment]

Standard 12A port sure looks small compared to a 13B!

I can now see exactly how much material is between the coolant passage and the port.



After widening and lowering the port the exhaust sleeve/insert appears to hinder more than help the flow. This is because it now is thin on the sides and bottom. It also has gaps around its leading edges.

Should I do without the sleeve?

j9fd3s

be nice to see it with the sleeve in. um i think ideally you want to open the port up to the size/shape you want and then the sleeve should just match it.



the stock way where it increases area like that is not so good

Lynn E. Hanover

The early housings have smaller ports and smaller sleeves. You can remove the whole thing and replace just the round ring at the port face with an aluminum ring and two TIG spots to help hold it in place.



You are looking for a 1 7/8" ID opening for the header match. For turbos maybe a 2" ID.



I would leave the whole thing in place for the later housings, just match up the inside end to match your inner exhaust port.



Lynn E. Hanover

bruceman

I decided to leave the inserts in and ground them out to match the new port.



Thanks for the replys.