I just picked up a set a couple weeks ago. Im under the impression that theyre 1 3/4, but Im hearing that they were never made other than 1 5/8. Looking at these things, they are huge compared to my Edelcrock TES, which are 1 5/8. Is this true?

Also, is the size measured from the inner or outter diamater of the primary?

 

Oh, and I also have a full set of pics I took of them incase anyone has never seen Tri-y's. I know I never did until I got them. Ill get them up pretty soon.

 

I.D. due to different gauges of tubing.

 

I've got them and yeah, the tubes do look larger but like it was said, it's the difference in gauge and construction of welds.
The headers are great, only problem is getting to some of the nuts and bolts for the y-pipe. The gaskets are still sold through SLP .

 

get some pics up i dont think I have ever seen a set of tri-Ys