welding header collectors

[RobM]

How does one go about welding a 4-1 collector onto a header? How do you get a full weld around all of the tubes? There’s no way that I can see to weld the inside. Here’s a picture of what I’m talking about.
http://www.burnsstainless.com/images/01100022.jpg

[parsonsj]

Here's how I did it:

1. tack the tangent points of the 4 tubes.
2. Using a torch heat the inside portions of the tubes and bring them together so that the inside portions make a cross. As you work the tubes "square" on the inside, tack weld it, work it, tack weld.
3. You wont be able to get them all the way together, so finish the inside portion with a small square piece of steel (or stainless).
4. Finish weld all the inside portion, smooth with die grinder if you wish.
5. Make 4 "V" shaped pieces of material to fill the 4 outer V shaped areas around the tube.
6. Fit and weld them into place. Slip the collector over the end, and weld it to the tubes and V shaped pieces between the tubes.

I've got some very grainy pics of this ... I'll post it.

jp

[parsonsj]

Hope this helps.

[parsonsj]

Or ... you can buy some merge collectors. They just slip on ...

jp

[RobM]

you dont have to weld merg collectors?

thanks for the picture

[parsonsj]

No, merge collectors don't have to be welded except to keep them from falling off. Exhaust systems only exert about 3 psi, so a decent sleeve fit is all that's necessary.

jp

[PTAddict]

There are quite a few folks who have experienced exhaust leaks with slip-on merge collectors. It is true that in an efficient exhaust system, the average pressure should stay below 2-4 PSI, but in a header tube the pressures can reach double digit PSI for brief periods during a single exhaust cycle, and very high vacuums occur as well. The result with less than perfect seal is annoying "tics" of sound as exhaust leaks during high pressure cycles, and potentially bad oxygen sensor readings due to air leaks during high vacuum periods.

Folks often advocate welding on such collectors, but it seems physically impossible to me to get a 360 degree weld around the perimeter of every header tube/collector tube junction.

Burns seems to think that if the slip junction is built to very close tolerances (like theirs), it will be leak proof. Maybe others with direct experience can chime in ...

[wendell]

JP, thanks for the pic. It was just in time. After an off road excursion the race car is ready for a new drivers side collector. Won't be as fun as starting from scratch but is cheaper than calling Stahl.

[parsonsj]

Folks often advocate welding on such collectors, but it seems physically impossible to me to get a 360 degree weld around the perimeter of every header tube/collector tube junction.

Burns seems to think that if the slip junction is built to very close tolerances (like theirs), it will be leak proof. Maybe others with direct experience can chime in ...

I'm using Stainless Works merge collectors. They are a tight fit, and I've done nothing to seal them. I don't notice any leaks (the ticking you mention is something I listen for). I continue to monitor this with visual inspections since my O2 sensor is within 24" of the joint.

jp

[RobM]

so merge collectors will also work in a turbo application correct? As long as they are of good quality....

how tight do these things fit? is it supposed to be an interference fit? or do they just slip on with moderate effort

[parsonsj]

They are supposed to slip on with moderate effort. Most guys put a tack weld or some sort of "can't fall off" thing on it. I didn't see the need since I put mine on by swinging a rubber mallet as hard as I could for several dozen swings. My tubes weren't perfectly symmetrical, so the farther I hammered the collectors on, the tighter they fit. As far as I can tell, mine haven't moved a bit.

jp

[David Pozzi]

Most race headers I've seen on road race cars use either some kind of tabs with a bolt, or springs to hold the collector on the pipes.

[RobM]

thanks for the info guys.