X pipe H pipe or side by side

ir3333 said
We were discussing scavenging,tuned Try Y,optimizing lengths,volumes,diameters
how 2 into 1 compared to 2 into 2 could work with some excellent analogies.
...Now we are "new Mustangs have them" , "Nascar run 9200 rpm" and "Hensley got
20 hp", that's O.K. and suggests they work but we stopped trying to "figure out how"

me thinks these things work better on smaller engines. but, a 68, 426 hemi roadrunner came w/ an h pipe on it ! over 500 cubes , I still don't think their worth their weight, provided your whole exhaust system is big enough! . jmo