TR2/3/3A 4-2-1 headers [or Tri-Y]

[Bremer]

One of the next items on my upgrade list for my 59 TR3 is an exhaust header (or extractor manifold, as they say across the pond). Reading about the differences in engine characteristics between 4-1 and 4-2-1, I think I prefer the latter because of higher torque in the low to mid range. However, I am having difficulty finding one at an acceptable price.
The only places I was able to confirm to carry this are Moss (expensive in mild steel and stainless steel) and Racetorations (mild steel only, even more expensive).
If you were in the market for one, where would you look?

Thanks!

 

[Bremer]

Anyone?

I guess I could build my own tri-y headers, but I am missing some design details such as diameter and lengths of the primary tubes. Any input would be appreciated.
Thanks!

 

[Monkeywrench]

Bremer,

A tri-y will absolutely be better, the problem is, there isn't anyone with what you want off the shelf. A custom tri-y is going to be a lot different than what you can get.

For a custom set, you want to use as large of bend radius as you can. This means 4" for smaller diameters and as you get to 1.625od tubes, you want to start using 6" bend radius. It's all about velocity management. The other thing is to make the transition from the head to the primary as smooth as possible. Match the shape at the port and have zero step. Also make sure the tube and the port exit at the same angle (not an issue with the TRs). Designed carefully, you'll make more peak power than any of the 4-1 headers and be WAY up on the low and mid range.

A race header for a wet liner TR engine would be somewhere around: 1.5 @ 12" > 1.625" 6" or so -first collector junction - 1 7/8" for about 30" or so before a choke merge collector and into the tailpipe. A street car / lower performance car would probably go down one size on all those numbers. Best to consult with Burns Stainless on exactly what you want. It'll cost you about $75 for them to run your numbers. There are cheaper places to get the tubing you need with that bend radius. Mordy Dunst should be able to make you a header flange as well.

Cheers,
Bob

 

[Bremer]

Bob,

Thanks for your reply, much appreciated.
I had indeed wondered where I could get a header flange from, and had forgotten about Mordy.
Also thanks for your tip to contact Burns Stainless, their website looks they have everything one might need for a custom header.
Can I ask you to clarify your statement about the diameters. I'm not sure what you mean by 1.5 @ 12" > 1.625" 6". Are you saying that the tubes from the header flange to the first Y should be either 1.5 or 1.625'' in diameter? What's the significance of the 12 and 6''?
I understand that between the first set of Ys and the last one the two tubes should be 1.875'' and 30'' long.

Thanks!!!

 

[Monkeywrench]

Yep! Those are just ballpark figures, Burns will tell you more. You want to match the port area (remember, calculate area of 1.5" which is 1.58" area (.040 wall tubing). A stock port is probably a bit smaller.. may want a 1 3/8" primary off the port. Make it square and let it transition to round, start at the top, then the sides, then the bottom.

Those first numbers are the primary. So step up at 12". You need the large bend radii to make those diameters work. The larger the bend, the more it can flow for a given diameter.

You want it as swoopy as possible like this, which is near impossible on a TR. Just try your best:

 

[Bremer]

Ok, thanks Bob.