View Full Version : Welding header tubes
08-09-2006, 12:47 PM
Building a straight tube header for my Olds Quad 4 engine project. The tubes are 9" long and 1/16 wall. The exhaust port flange is 3/8 thick 17" long mild steel. Figuring TIG would be the way to go. Any ideas on amps and filler rod to use. I have heard guys using MIG also to weld the tubes, which process would be better ? The tubes will be flush on the plate. Thanks for the help.
08-10-2006, 10:38 PM
I've welded these with a MIG from the back side rather than the old time gasket side weld.
My dial has 6 positions, 2-3 is sheetmetal. I probably welded with a 4 and kept most of the heat on the flange and weaved into the tube a bit for good fusion.
I did a 2300 Ford flange that was ground flat prior to welding and bolted to a head during welding. All I used was high temp silicone and no gasket, works great. Cut flanges generally have warpage from cutting and the steel does not start out flat anyway.
2.6 Chrysler / Mitsubishi Laser cut flange had warpage, didn't have access to a surface grinder. Ended up cutting the flange into 4 sections ( 2 bolts per section ) bolting the parts to a head and welding from there. Used a stock gasket because it has a heat shield for the plug wres built in.
If you need to section the flange, make sure there are 2 bolts per section. If this isn't possible, cut across a bolt hole then use a thick washer under the bolt. ( this way you still have 2 bolts per section.
01-19-2007, 05:12 PM
Most people use plumbing bends in T304 stainless schedule-10. With mild-steel flanges to keep them from warping & cracking profusely as they're heat cycled.
store.racing-solutions.org for more traditional pipe.
Once welded together (Like he said) you can cut them apart, or grind / mill them back flat.
But as they heat they're going to warp to some extent anyway. The best thing to do 9If your own car) is to bolt them up to the specified torque, give them afew heat cycles. Re-torque them. At that point if they are not leaking. You'll never have a problem out of them.
You will pull small warps out of a flange when they are bolted in. Most call for 15-17 lb-ft.
Have a good copper, or mult-layer steel gasket too. Copper sealing spray can help if you have gasket problems from poor surfaces.
GTAW is better. Takes alittle longer, but it's completely inconciquential with exhaust parts. You spend little time welding exhaust components together. You spend the majority of your time routing, cutting, fitting & tacking the pipes together to get your final fit. Running 2 passes on your joints just does not take all that long.
And please do the math behind your tube choice, and sizing!!!
I hope you don't mean to use 9" long primary pipes, and stop there. That would be tuned to put your peak powerband more 9000-9500rpm ish on most engines which. I highly doubt you attent to want those headers tuned to maxamize their gains at! That's... Stupid! Only time you can get away with short primary pipes without much sacrafice is in a turbo manifold.
Depending on the I.D. of the pipes. The vast majority of the time, your primary pipe length should fall around 28-36" in length to maxamize the velocity and hence the gains from the headers to around the 5000-6000rpm range. (Which is where almost all gas engines are setup to dance through during gear changes) Your typical 1.25-1.75" primary pipe size will fall yet again to right around 32-34" in length.
As far as collectors... Please cut them out correctly. The longer they are, the better you'll be. A "proper" collector will generally be 9-12" long. Not 2-4" long like you typically see.
If you're going to do something, do it right!
If you want, tell me about your setup, and I'll do most of the work for you. :P
In fact... If you can give me a dyno of that engine, or a simlar engine. I'll get you REAL close to what the ideal setup would most likely be. That way you don't have to play with it much.
What's the ID of your pipes & what gauge, or schedule # are they?
The three biggest mistakes people tend to make are:
Far oversized I.D. head ports & primary port sizing. (Velocity is the key. Velocity, Velocity, Velocity. Velocity determines everything. Once you've maxamized velocity without harsh resistance, bigger simply means slower.)
Primary pipes that are much too short.
Grossly made, or bought collectors / merges.
01-22-2007, 12:28 PM
Thanks for the info guys. I like the idea of welding on the tube side,will be much easier to seal. The tube I have is .0585 thick and 1.5320 ID I wil need to flatten the tube to make it fit the oval 2 valve exhaust port. Have some sheet copper to make a shim/gasket out of.
Going for short stacks with 3 inch supertrapps , more of a running display engine than a tuned torque monster.
01-22-2007, 05:22 PM
1.5" is perfectly happy to support for 60-70hp/cylinder N/A. You see alot of 1.75"-2" primary port sizes, but any more than 1.5" & the velocity tanks alot without really paying for itself later on.
On the collectors. 3" is *extremely* short. If you've got a 14" chopsaw, or a 4-6" bandsaw, you should be able to cheat & make a very nice 5-6" long collector. Comes out better on a bandsaw, but whatever.
01-22-2007, 06:28 PM
01-23-2007, 06:34 AM
Some day I hope to be able to produce workmanship like that.
01-23-2007, 12:52 PM
A true work of art. You are a fantatic fabricator. You could work for any Indy team around. Thanks for the photos !!!!