I started to make my custom extractors for my engine today, I spent about an hour and I am realy happy with how far I got considering the standard I made them to.
I decided I would go for 1.5 inch primaries and 2 inch secondaries, I would of gone for 1 3/4 secondaries but 2 inch is a size I already have in mandrel bends.
Heres what I managed to do:
2 x 1.5 inch inlet and the exact size for a flattened 2 inch for the exit. I didn't have a peice of 2 inch stainless at the time so I used a peice of mild as a template only.
A view from inside, I will do some more finishing later once its welded.