header tube size question,

[moparian]

1 7/8 step to 2 in with 3 in collectors 422 ci over 750 HP,yours are fine for what you have

[F-BIRD'88]

When you run thru the traps. What is the max rpm?
When you run thru the traps what is the intake manifold vacuum at the stripe @WOT?
(Accurate high resolution manifold vacuum guage)

1/8th,? 1/4 mi ?

[Newold1]

I think as well as many others here that 1-3/4" primaries are just fine and the 12" collectors will have a max torque versus rpms influence but not that much. I suspect the shortfall in performance you are experiencing is coming about from elsewhere in the car or engine. Simpler test is to put the car or engine on a dyno and print out the result with and without a long collector. TEST,TEST,TEST - NO GUESS, NO GUESS,NO GUESS!

[F-BIRD'88]

You still will not know if the collector us correct or not.
Test it at the track. Take a different collectir with you to test also. If the different collector sliws the car it tells you just as much as if it speeds the car up.

[chevy art]

thank you again to all the members that responded to my question. here in NY its just about time to go to the track(April 30) and i will run with the 12 inch collector, a 16 inch collector and no collector and see what happens. ill respond back after i go to the track in May aert in NY