I'm curious as to people's experiences (good and bad) with homemade turbo headers/manifolds, crossover pipes, downpipes, etc.

What material did you use? How thick?
Tig or Mig welding?
Any expansion joints?
How long have you been running it?
And of course, how has it held up?

 

My single turbo manifold is made out of mostly thick wall steel pipe. It's very heavy stuff. When I got the manifold around 1998, it was already 10-12 years old and had a single crack down one of the tig weld beads on cylinder #4 (where the tubing welds to the flange that bolts onto the head). I tig'd this area before installing it a couple of years ago. After 11k miles of use, it has not only cracked in the same spot again, but now also has a crack at cylinder #1 running across the weld and outward about 3/4" down the tubing. Neither of these cracks are leaking (even with 50 psi of measured exhaust pressure) . #4 crack is only partially into the weld and is outside only. #2 is cracked all the way through the tube from outside to inside.

The reason I have the manifold off right now is that it is slightly warped down the flange. I'm having a machine shop add material to the flange and then machine it smooth. I guess my point is you might want to look at 321 stainless if you're thinking about building one!

 

Holding up ok. Had it on about 2 years but kinda limited usage until this year where I actually drove the car alot more than I did the year before due to problems last year. No idea of the mileage but every time I take it out, I beat on it. Glowing orange its working No cracks or leaks and the manifold seals to the head fairly well. Had a few minor exhaust leaks develop due to loose bolts backing out over time, but i'm happy with it so far.

16 gauge mild steel header tubing. 1.75" diameter. Hooker stubout flanges about 3/8" thick I believe but lightly milled to flat after welding.
Most of it was tig welded but some parts mig welded. Had to patch a few pin holes with the mig and the T4 flange welded to the collector with mig welder.

No expansion joints on headers or downpipe until about 4-5 ft down in the exhaust, I have a single flex joint to allow for the exhaust to wiggle. Works great.

Redoing my setup now using mild steel again but making more of a collector design. MAY need flex pipe in between the manifold and turbo this time depending if my mounts hold up to the heat.