Header length versus diameter

[treessavoy]

We were all lying to each other about our racing past when the subject came up about which hurts the engines the most: header tube diameter or unequal tube length.

How much would a equal length header lose if it was 2 1/8 vs 2 dia.?

How much would the same header lose if it was optimum dia.but unequal length?

Which situation is worse?

It was a lively argument with no real answer, Help!!?

JimR

[FINESPLINE]

Interesting post. Just to generalize, I believe every motor depending on what you want out of it would be different. The combinations are endless as far heads , intake and carb. cam timing and operating range on just one engine combination. Header size ( diameter, length and collector size and design ) can very greatly. I am sure A56 will read this and chime in. Bottom line, there are people who specialize in that area and do the R & D and we pay for there knowledge. Will definitely be following the postings !

[Jeff Lee]

You could have the primaries +/- 1/8" in length and the diameter computer model perfect. But if you build it with sharp bends out of the heads and other areas along the way, you will have something that still needs work. It's the finished product that counts, not the sum of it's parts.

[jmcarter]

You guys are spot on and I'd call Lelchook (A56) if I had a specific combination in question. He is a wealth of knowledge on header technology (and his stuff a work of art ).

[gmonde]

I have built a few sets for a different makes chevy, dodge ,amc ,,if you have a dragster or an altered taking advantage of the open space you have to make each tube equal lengths with the same angle bends on each tube that is the perfect header exhaust pulses getting to the collector with that perfect exhaust pulses ,,but in a door car stock engine bay you always try to get that that same result but in some designs I see the header builder try to get that equal length and some times has one or two tubes that extra bends or tube routes that reduce exhaust flow ,with other tubes taking a more direct route to the collector ,,one other area sometimes neglected are the primary header tubes welded the header flange can be somewhat desirable flow conditions ,,,its all about planning your best route ,,having built a few sets ,it is easier said than done ,,the only way to really know is bring a few sets to the dyno ,, different sizes and dragster header vs stocker header www.gmondeperformance

[FINESPLINE]

Thanks Mark !

[treessavoy]

Thanks Mark, Guys,

Street headers usually have varying tube lengths, some may be more than 2" difference how bad does that hurt the HP. Equal length competition headers may be 1/8th of an inch or wider diameter than usually used for that application, say 2 1/8 vs 1 7/8. How much effect would that have on HP?

JimR