Typical header dimensions
 

What’s the typical header sizes used on an A stock bbc?
I run a 402 in my bracket ride and am using a hooker comp header with 2” tubes & a 3”1/2 collector.
Turns low 10’s at 130 plus

Re: Typical header dimensions
 

Looks about right.

Re: Typical header dimensions
 

Sometimes 2 1/8 on our Max Wedges -I would think
maybe a bit bigger than 2" on Big Block GM.

However, I have not raced a big block Chev. since early 70's
so what the Heck would I know. Maybe a Step starting @ 2" and
going up?

Re: Typical header dimensions
 

I’d been wondering if the collector is too big @ 3”1/2

Re: Typical header dimensions
 

I would say no....

Re: Typical header dimensions
 

I agree with Billy.

Re: Typical header dimensions
 

A "stock" BBC exhaust port is right at 1-7/8 in it's major dimension, maybe slightly more or less.
(Measured with a tape.)
So there's that...

Re: Typical header dimensions
 

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

Re: Typical header dimensions
 

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

Re: Typical header dimensions
 

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

Re: Typical header dimensions
 

There's faster pipes than Hooker.

Re: Typical header dimensions
 

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.

Re: Typical header dimensions
 

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.

Re: Typical header dimensions
 

PM sent Jim.

Re: Typical header dimensions
 

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.

Re: Typical header dimensions
 

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

Re: Typical header dimensions
 

What class do you run BParker?

Re: Typical header dimensions
 

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

Re: Typical header dimensions
 

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

Re: Typical header dimensions
 

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!

Re: Typical header dimensions
 

Years ago my brother crushed a primary tube taking the car out of a trailer. He ran the car and it did nothing to the ET. BP