Bill, your setup an mine are day and night different (blown hemi with direct drive), but I'll share what I have learned. I also started with low % nitro and pretty quickly worked up to 40-50%. ET gains came with each jump in %, but the MPH gains were more significant.
When I moved from the 7.50 class to 7.0, I increased to 70-75% and added a bunch of clutch to it. To make more power you have to have more fuel, more fuel wants more clutch, more clutch wants even more fuel, and more fuel wants more spark energy. It all has to play in the same sandbox. Somebody mentioned your convertor and for sure, you will want it tighter for fuel.
My best tuning aid was when I took off my mag IV and put on an old Schiffer-Cirello unit for looks. It would put raw fuel out the rich cylinders and I was able to balance the fuel system much better. When I got to higher % I had to go to a mag V to keep the holes lit. I have a mag + that I'll likely switch to.
I also see a drop in ET if it's tool long between the warm-up and a race and the cylinder head temps drop too much.
My opinion is that it's much easier to run nitro with a blower, but the injected guys might have a different opinion. Just be sure to pull your plugs and clean out the chambers and lines before trying to start it. Also, if you have gas ports in your pistons I have heard of a case where they caused an issue with nitro.
Steve K.
