math to building headers.

[sasquatch]

is there any "math" to building a exhaust header? like volume of the tube and the point where all the tubes collect?

[JPT]

There is. Whole books have been written about this. I have a few formulas, but I don't know how good they are. I'll see if I can find them and post some later.

[FestYboy]

look at accoustical tuning of bass tubes for an idea on what you're getting yourself into.

[solatare]

unless youre building for a high dollar race car you plan you making a living with, i wouldnt worry about the math, just look up headers for engines of about the same size and reference the runner diameter and primary length, tri-y headers are excellent for 2-5000 rpm range and boost torque, 4to1 or 4-2-1 designs, like what you see on hondas, work best for higher rpms, over 4000, also a very small, say a 16th inch, step where the header primary joins the flange helps scavenging.

[TRUCKtiva]

also a very small, say a 16th inch, step where the header primary joins the flange helps scavenging.

Can you define what you mean by "step" ?

[FestYboy]

smaller pipe going to slightly larger pipe (a slip joint weld) keeps pulses from reverting all the way back to the exhaust valve (reversion of gasses)

[sasquatch]

im gonna build a set for my b3 and then when i do my bp swap build another set. so what size and thickness tubing should i use on the b3 and the bp?

[jrbauerjr]

Sasquatch,

Yes you can build headers quite easily, JCWhitney used to sell the bends, joints, outlets and all the rest, I haven't checked it in many a year. But, the tube diameter is directly dependent on the displacement and the length is dependent on the rpm range (pulse frequency). Screw these up and I guarantee you'll turn in worse numbers then the stock pieces.

Good starting point: http://www.amazon.com/Scientific-Exh.../dp/0837603099

Jim Bauer

[NovaSS]

google "header calculator" or variations of that theam, there are several online were you just "plug the numbers in", some calculate diameter, some length.

NOTE some are calculated assuming its a V8 so you may have to double the 1.3 or 1.6 you are using to get the correct numbers. On anything you are running on the street is best to lean towards a smaller diameter and longer length.

As for supply check around and get mandrel bent sections and the thicker the better.

[FestYboy]

as far as materials, i've been looking at conduit tubing. it's thick and cheap and comes in the smaller diameters needed for our small engines. the JCW kits are designed for V8s and the primaries start at a diameter that too big even for our secondaries.

[sasquatch]

what size (ID)should i go for and also what thickness? i was thinking 1.5 inch (ID) and 3/16th thick.... dose that sound good? maby 1 and 3/8? btw this is for the b3....

[sasquatch]

anyone?

[FestYboy]

your primaries should be an inch or less (ID) and 3/16" will be very hard to bend. i think they make 1/8" wall or possibly 3/32" in the sizes i'm talking about. even 1/16" wall would work better than the #16 ga. that most companies use. figure this: ID of the primary should be between 70-80% of the exhaust valve diameter for a mild street engine (of course you'll port match as well).

[solatare]

16 or 14 gauge steel is fine for a header that doesnt have to support a turbo, ceramic coat or wrapping will help it last longer and work better by holding the heat in and slowing the heat cycle. 1 inch primarys about 30 inches long should work well, and if it were me id do a tri-y type since the b3 and b6 powerbands level off at 5k rpm and that will give you the best overall gain between 2 and 5000 rpm. flange to head should be 3\8 or 1\2 inch plate. id go with 1\2 since it gives you room for a seal weld on the inside and that step id mentioned earlier and will not warp as easily.

going for a turbo id use sch-80 pipe in a log manifold, sch-80 has a 5\16ish wall to it.
forget bending any pipe much over 1\8 wall, you need a press with a special die and hydraulic tensioned mandrel to do it cold, i would not heat it, to much risk of making it brittle, if anything buy a pipefitters handbook and section everything. lots of welding and labor, but it looks cool and flows well.

[sasquatch]

ok i think ill make up a set soon. im gonna make one that sort of looks like this:

http://www.ultrarev.com/files/images/product_thumbnail/t_48316_01.jpg

http://www.jaydm.com/assets/dc/4-1cc1.jpg

i think they would sound GOOD ill update as i go along.