I was wondering if I should use a s4 upper and lower or a s5 upper with s 4 lower on my track car? Any help? It is a s4 6 port na block, that I might turbo at a later time.

 

Bump

 

try both! the upper manifolds interchange, so you can run the lower intake of your choice, and then try each upper.

 

I dont have much to ad to this fight, but ive heard that the S4 lowers have shorter and more direct runners. To maximise my de-actuated S4 lower, I removed all my 6-port actuators and associated nonsense , filled in all the remaining holes with JBweld and smoothed and ported the remaining, as well as also knife edging the small divider between the pairs of secondary ports

 

Thanks, any suggestions on which porting to run on a track only car, we run in the chumpcar endurance series.

 

if you aren't limited by the rules, go peripheral, everything else is a waste of time...

with the S4 vs S5 manifold you're talking about the difference between 155 and 160hp, with a peripheral you're starting at ~230rwhp.