RE: Problems with Rossi 61 RIRE
squid1,
I'd mount a fine-balanced 9*9 APC for pipe tuning purposes. Which pipe do you use? Are pics available?
If the pipe has a biggest diameter of approx. 42 mm then I'd start with 310 mm distance from the glow plug to the weld seam of the double cone or the deflector plate respectively. Then shorten the header in 5 mm increments until the rpms begin to decrease. That should happen at about 290 mm. 10% nitro should be OK.
Do you use pipe or crankcase pressure?