Header primary tube size

[Bent77]

Considering my goals I think the 1 5/8 would be the minimum, I know on a dirt bike exhaust is used as a tuning tool, and it has a major effect when you change diameter and lengths, but we're talking about serious power from small displacement and overhead valve or two strokes, that might be an apples to oranges comparison. But still I cannot find the hedman in a 1 3/4 primary so I am not going to split hairs, it don't think it's worth it.

With what you're doing, 1 5/8".
I'm guessing there is not a stepped secondary option without building them to the truck. This would likely yields the best results

 

[wetoolowdingbangow]

With what you're doing, 1 5/8".
I'm guessing there is not a stepped secondary option without building them to the truck. This would likely yields the best results

You can make up some difference in the collector. It's increments are considered to make half the difference of a size jump in primary.

It's all splitting hairs. Rch ftw!

 

[Bent77]

You can make up some difference in the collector. It's increments are considered to make half the difference of a size jump in primary.

It's all splitting hairs. Rch ftw!

Different sized primary, stepped secondary and a megaphone collector FTW!

Spent an entire day on a dyno once just messing with headers on a SBC

 

[wetoolowdingbangow]

Different sized primary, stepped secondary and a megaphone collector FTW!

Spent an entire day on a dyno once just messing with headers on a SBC

From what I gather...and I'm no expert.

Small changes can add up but a majority of them are so close together it'd be hard to notice the difference when driving. After looking at cylinder head comparisons and so on, the difference in runner sizes weren't crazy jumps in power. That said I saw an article on mix matching the wrong components it clearly takes a lot of wind from the sails.

 

[Bent77]

From what I gather...and I'm no expert.

Small changes can add up but a majority of them are so close together it'd be hard to notice the difference when driving. After looking at cylinder head comparisons and so on, the difference in runner sizes weren't crazy jumps in power. That said I saw an article on mix matching the wrong components it clearly takes a lot of wind from the sails.

I know enough to understand it gets expensive to get any useful gains messing with the tube sizes.
Being able to try that much on a dyno was pretty cool. We learned a lot. Car picked up .40 at the drag strip the next season