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I wanna replace a T4 turbine housing with a T3 housing (at the moment for a Stage 5 Wheel). The turbo is equippt with a P-Trim exhaust wheel. I know, i need to do some machine work to make it fit. (Don't worry, i don't wanna do it myself, i've a machine shop which will do it for me with the right tools).
I measured both housings. I know now that i need to bore out the smaller hole to make the P Trim wheel fit into. (In the Picture marked as "e" for exducer).

The bigger hole has different diameters, too. The curious is, the T3 housing (for a stage 5 wheel) will allready fit over the major side of the turbine wheel. Do i need to modify this side, too? Or can i leave it? (in the picture marked as "m" for major) How much clearance need to be there?

And finally the distance of the base of the bigger hole (major) to the upper edge of the smaller hole is different, too. (Look at the picture at "h"). Curious here, on the T3 it's around 2mm more far away than in the T4 housing!?



I know someone allready have done this. Can you help me out? Any hints or guids?

Maybe someone can show me a picture of his H.O. turbine housing?

TIA