BTW, the OEM cast iron maniflod pairs cyl. #s 1 & 4 together and cyl. #s 2 & 3 together.
Same with the SAM header
So the OEM ex. mani. & SAM are the same as far as cylinder pairing in the "4" part of 4-2-1.
SAM uses 1.70" primary tubes, and OEM ex. mani uses 1.60" "primary tubes" in the cast iron ex. mani design.
Secondly, the header pipe that bolts to OEM ex. mani is the "2" part of 4-2-1. SAM header is 2" pipes, where the OEM is 1 3/4" pipes .
Thirdly the collector is the main difference between OEM ex. mani & SAM header design.
So if I make the OEM exhaust manifold lentgh + the header pipe's 1 3/4" pipes equal the full length of the SAM header from cyl. head to where dual pipes meet the collector, & make the collector like the SAM collector, I'll have basically the same header, only with OEM parts+ a little modding.
What do you think about that?????????????