I know that nobody uses the 6 port 13B irons in racing, although streamlined plugs for inside the turn into the chamber for street racers were available. The extra ports are opened at high RPM to add to peak power. The stock plugs open by twisting in the tubular port. Many wire the extra ports open and tune around the flat spot generated by low port velocity. I have not seen a 6 port Renesis  iron in person and do not know if any paths are available to modify them.

Again to improve high RPM HP. So I would lean toward 4 port irons or use all 6 ports in your irons. There may be pictures on the net of successful porting done to the 6 port irons.

 

Lynn E. Hanover

 

Hi Lynn,

I have a 6-port Renesis and was wondering if I would have to fill the two extra ports or just leave them stock and cover them with intake flange?

Dale Harvey