My d port headers I built use the hedman adapter plates, have 1 7/8 primary than stepped to 2" od than 3.5 collectors , I didn't think a full 2 was needed, about 550 hp, now with new heads should pick up another 100 hp and leaving them alone. . Header design especially equal length tubes play a big part
__________________
Illinois Outlaw Gassers
6.27@107
9.97@131
|