redliner wrote: ↑Wed Oct 04, 2017 10:18 amHey guys I am getting ready to build a new set of headers. I have a sbc with a 4/7 swap in the firing order and I would like to place the primary tubes in the collector in the order which helps evacuate the cylinders the most effectively. Am I over thinking this or..... I have the pipemax program which has told me the diameter and length needed but I wondered about placing them in the collector in a certain order... These fenderwell headers for my 42 Stude coupe will be 2 " for about 10 " then 2- 1/8" for about 20" finishing with a 16" 3- 5/8" collector.
the main reason why your calculated Header Specs are larger than a ProStock Truck 358I was shocked to find out that the 900+ hp ProStock truck 358 was running a primary of 1.625,
I don't know what the step lengths were but It was smaller then I would have ever guessed.
is your Compression Ratio is only 11.5:1 -vs- a ProStock Truck 358 's 15:1 + Compression Ratio + the VE% is way less than a ProStock Truck 358
this will cause your EGT's to be higher , making a larger diameter tube necessary .
i ran a 3-Step 1.875,2.000,2.125 3.500 Collector on my 355cid with 13.7:1 CR
so a 2-Step 2.000,2.125 3.500 Collector is very reasonable
i've run that much Header on many 377cid to 434cid with great Dragstrip and Dyno results .
Also you made a mistake on number of Intake and Exhaust Valves per Cylinder
your Inputs should have a value = 1 per Cylinder , but you entered 2 Intakes and 2 Exhaust Valves per Cylinder