Typical header dimensions

[Terry Cain]

Originally Posted by 1uke

I’m hunting around to drop up a tenth or 2 that’s all.
Maybe grasping at straws during the winter boredom....

There's faster pipes than Hooker.

[Jim Caughlin]

Originally Posted by bert powell

My SS 402 likes 1 7/8" step to 3.25 throat merge collector for what it is worth.

As a header builder who has built several sets for these types of combinations, I think your sizing (1 7/8 with merged collector) is probably correct. 2" primary with 3 1/2 collector is likely too large. I am constantly trying to convince people that they want too large of tube sizes.

[bert powell]

Originally Posted by Billy Nees

And I'm guessing that it's an oval-port combo?

That's right Billy, that is why I said for what it is worth. You are dead on with the 427/425. I just noticed he had a 402.

[Barry Polley]

PM sent Jim.

[Kenny Wigington]

Does anyone still use the exhaust valve size in the calculation ? I heard that for years. It made some sense, as far as primary pipe size.

[B Parker]

Originally Posted by 1uke

I’m hunting around to drop up a tenth or 2 that’s all.
Maybe grasping at straws during the winter boredom....

I run a 402 BBC in stock. I use a 1 7/8 to 2 inch primary. I'm sure you are not that far off with a 2 inch Hooker. Most of the guys that run BBC high HP cars in stock use a 2 to 2 1/8. I would be surprised if you could pick up a tenth with a header change. For the kind of money you would spend on a good set of headers you could find more ET with something else. BP

[Bob F]

Originally Posted by B Parker

I run a 402 BBC in stock. I use a 1 7/8 to 2 inch primary. I'm sure you are not that far off with a 2 inch Hooker. Most of the guys that run BBC high HP cars in stock use a 2 to 2 1/8. I would be surprised if you could pick up a tenth with a header change. For the kind of money you would spend on a good set of headers you could find more ET with something else. BP

What class do you run BParker?

[B Parker]

I run A and B stock auto. I believe I have one of the faster ones but with the AHFS most of us have blocks under our gas pedals. BP

[Randall Klein]

A little off topic, but just wondering anyone's opinion on dimpling tubes to fit.

Engine Masters (Frieberger) has video on just crushing tubes to little effect

[GTX JOHN]

Jack Davis (RIP) told me that you could ding the Header quite a
bit without hurting Air Flow.

He has been gone a while but I still replicate the Step headers
and Merged Collector he made for me on all my cars!