Quote Originally Posted by DA BIG ONE
Art, The GM-8 exhaust turbine "exhaust outlet" is some of the limiting factor needing some porting. How much porting? It's more a matter of how much risk one is willing to take making walls too thin.

Some say the elbow after the gate is an issue, then some smoothing out of its inside surfaces are in order.

I really thing wee need those bigger Holset 35, 40 turbo's providing we stay out of the surge line, and keep boost at a level of 15+- psi @ intake.
If the GM-8 seems to run out of steam at 2800, were does a GM-8 run out with a free flowing exhaust? Mine definitely seems to lose it by 3100, maybe 3000.

Art.