Dyno Run shows very rich at low RPM but...

[Sledge]

...a little lean at high RPM. The pull was shut down at 6000 RPM, didn't go to the usual 6500. It was a club-sponsored dyno pull so no time was available for tuning.

So your help and advice are requested as I am NOT a carb expert.

On the dyno WOT was applied at about 3000 RPM and the AFR was 13; by 4100 RPM the AFR was 10.5; back to 13 AFR by 6000 RPM.

The carb is a 4150 HP-based Pro Systems 750 w/mechanical secondaries. I e-mailed Patrick with the dyno run printout, his advice was:

"The best plate (sic) to jet is really the racetrack. Jet up or down evenly 2 jets at a time and jet for best mph."

I don't have a handy racetrack so I'm doing the best I can.

Over the last week I've been trying different smaller primary jet sizes, but I notice more severe surging at 1/2 to 3/4 throttle with the 72 and 70 primary jets than with the 74's that came with the carb. At WOT it goes great, right up to 6500. I haven't tried a 75 or 76 yet. But I'm wondereing, should I also be looking at the secondary jets and trying some changes there? I haven't done anything there yet with the 84's that came with the carb. Should I try going larger with the primary jets and smaller with the secondaries?

I get lousy mileage and am ok with that if the performance is there. These dyno runs showed 16 less hp than previous runs--on a different dyno--with a Street Avenger, no cold air box, and more restrictive mufflers--but about 40 more lb-ft torque. I was hoping for better power but I'm thrilled with the increased torque.

Should I keep fiddling with the jets or should I be looking elsewhere? Ultimately I know I will probably be heading back to the dyno and spending $$ but if there is something obvious to those of you who are knowledgeable, I'd appreciate it.