Originally Posted By Cab_Burge
I think AndyF has, maybe not confused I've dyno tested motors with both but not on the same motor shruggyI think the 3X is for large C.I. motors, probally above 511 C.I. confused shruggy
the one motor I assembled and dyno tested the 3X was a 4.5x4.5 World block with right at 15.0 to 1 compression on race gas, it had uneven fuel distribution problems on # 2 and #7 cylinders according to the EGT and spark plugs work Bob Goerge could, and can, probally fix that up scope


Hi Cab. I believe the X manifold is more effective on larger CID engines, but Indy says it is a power booster on engines below 600cid as well as being suited for engines above that displacement.