Originally posted by mic
I just found out that the GTK 650 uses a T3 hot housing. Unfortunately I have a T4 header flange.
The newer turbine flow rates are so go that you can drop the housing a/r and still get great spool AND good top end flow rates. The really small a/r's drop to a t3 flange.
You can either weld on a t3 flange, or get/make an adapter.
I actually have this specific adapter drawn up in solidworks for non-pcar specific projects. I can convert it to something you could use on say emachine's website to get one made cheap. Whipped it up for a different t4-3 conversion in the past(Rajay to Turbonetics)