Header calculations

[ikessky]

I know there is the equation on the link off of the main page, but that only deals with the optimal tube length. Is there a different equation for the size of tubing you should use for headers? This is actually going to be for a different engine (my little 4 banger dune buggy project), but I figured someone here must know the answer!!!

[Anonymous]

According to Ed from HeadersByEd, equations don't work. You just need to learn what you want from them. On my headers I was aiming for all out high end. I could give a damn about power below 3,000rpm. So I chose a mild diateter, 1 5/8". AS far as length goes, that depends. I used a short length, only 30". This is all high end, in fact ben said when he makes his he plans to go longer. With a lot of cars it all depens on how much room you have. I assume in a buggy you have good room.

If it were me on an average 4 banger, maybe 150hp, I'd use 1 1/2" D priamries, this will give awesome midrange. Then use about 36-40" lentghs, this also will give good midrange. on a dune buggy you do not need a strong high end as much. but a 40" length will still give a good mid and high end gain. But you really just have to investigate and figure it out.

[ikessky]

I should also mention that they will be open headers with no collectors. Just 4 pipes sticking out!

[v6h.o.]

one of my good engineer friends worked out the calculations for my headers based on my specific camshaft and engine setups:

his calculations were:

Here's some numbers I've crunched....

Using the intake valve area, I've estimated peak power to come in just a tad below the 5k mark, 49xx. Using this as the point where we should have the header tuned for, the following results come out:

Comp Cams Cam(16-233-4):

Primary Length: 38.6"
Primary ID: 1.50"

Crower Cam(03043):

Primary Length: 35.25"
Primary ID: 1.57"

How do those numbers match up with your desktop dyno program?

The lengths seem pretty long, do you have enough room to gather that much pipe under your hood? If you don't, your next bet is to work with a 1/2 octave of the pipe so it's tuned for every second pulse, just simply chop the length in half...

Let me know if you want some different RPM's or anything calculated out.

as to the formula's and equations he used.... i hanvt a clue...

[ikessky]

I'll have to do a little measuring. Both of those diameters sound a little big. How much bigger than my exhaust ports do I really want to go with the tubing to keep a good velocity going? I know you can't go too big otherwise the gases will sit outside the exhuast ports.