JIMB

iTrader: (2)

Not wanting to start a huge debate but I want to build my own headers.

Details of the car.

67 nova with heidt superide II and four link rear. Good clearance at the subframe for larger tubes.

RED sleeved LS2 to 4.125" and 4.00 Manley stroker rotating assembly.

LS3 heads, 227 intake and 236 exhaust with .620 lift and 114 lsa cam.

LS3 intake soon to be ported by Peak.

Level 4 FLT 4l60e with 3:50 gears.

I need best guess, recommendation on primary size.

I'm thinking 1 7/8" primary stepped to 2". Too big?

1 3/4" to 1 7/8" ?

Merge collectors or 4 into 2 into one collector?

Not a race car but a real snappy street car that my wife will drive.

Trying to plan for future CNC'ed L92 heads or AFR.

DaleTx

I would go with the 1-3/4" to 1-7/8" design. The smaller diameter will help to improve power and response at lower rpm's... and you won't give up much at the top... considering the cam you are running. I have a 427" with 1-7/8" Kooks. I would have used 1-3/4 to 1-7/8 if Kooks offered them.

For your engine set up, and gearing the 1-3/4" stepped to 1-7/8" would be good.

DirtyDirk

In the dyno section there is a back to back comparison 1 3/4 to 1 7/8. The 1 7/8 had more peak horse and lost very little in low rpm. I would like to see a comparison with 1 7/8 stepped to 2.

Blackpanther99

iTrader: (8)

1 7/8s have been proved to be better in most cases. 1 7/8s will suit you better.

6D9 Matt

I agree from what I have read the best bet would be 1 7/8"

JIMB

iTrader: (2)

Local Ford guru also reccommed the 1 3/4 to 1 7/8 stepped headers. He is a dyed in the wool ford guy but has a engine dyno with many hours of dyno tests that said medium size is the best overall.

Any thoughts on merge collectors? How about 4-2-1 collectors? I think I have room for either.