Originally Posted by Strongjeff
i dont think its the design of the engine that causes the loss of tourqe in the 4.0. I think a lot of it has to do with the heads on the 4.0, i have seen plenty of inline engines benifit from headers. Also header design is very inportant
Your header deseign theory seems to be true. On both my F150 and my WJ, the stock manifold was pretty good. On both its a form of the "tri-y" type configuration. Except 3 into 2 into 1. However I don't think a portion of torque comes from the heads I think it's got to do with the fully vertical cylinders resulting in direct transfer of energy into the crankshaft. Where as V styles the cylinders are offset from the crank. Resulting in energy loss due to excess friction on the cylinder walls. This would explain why V's have to rev higher to obtain the same amount of torque. But this is just just a theory.
2001 Jeep Grand Cherokee (WJ) Laredo, 4.0L, L6, 4x4
2" Rough Country Lift, 245/75/16 Firestone Destination A/T's, 100% Straight Piped, 10" Kicker Comp Woofer, 10" Ported Kicker Truck Box, 250.1 Kicker DX Amp, JVC Head Unit, Spectre Intake