Here we see the 2007 Challenge engine on the dyno cart with the first carb we tried, a Barry Grant 556-3020, a 850 cfm annular discharge, vacuum secondary unit. The carb, which was not set up during the initial dyno pulls in Portland, proved to be too large, and way too rich, at 9.5 AFR. Therefore, we used up our tuning time between the 3 preliminary pulls and the scored pulls changing out this carb for the 750 BG that the engine was originally tested with. However, the annular discharge concept was proven, as it did have more signal on the low end,  picking up horse power and torque. If we had chosen a 750 of the same type, we would have been much more successful, as the large and rich 850 lost power and torque accross the board in the mid range and top end. The change over to the original test 750 gained us 41.1 points.