your getting me confused now
you mention a 4150 carb "double pumper" then you mention a 4160 "vacum secondary.so what is better for my tunnel ram double pumpers or vacum secondary carbs. i don't think there is room on a TR1-X for 2 inline double pumper carbs.the vacum secondary carbs i've got now the bowls are seperated by less then a 1/2 inch between the front and rear carbs. so your saying a 600 cfm vacum secondary carb will be to much and i should go down to a 450cfm vacum secondary carb for better results.i bought 2 matched 600 cfm vac sec. carbs off of ebay for a good price and all they need is a rebuild. the camshaft that's in my motor right now is the GM #140 solid lifer cam and my compression is 11.5:1 and my rear gear is 3.73.