I did a bit more testing with the mule the last few weeks. I tried a modded up 850 thermoquad and got within 10hp of the 850 holley. The carb did not like the adapter at all. I made up a spreadbore plate to bolt up to a 4500/4150 adapter and it made things even worse dropping the hp down to 405.
Pulled that off and reinstalled the 850 holley with the 2" open spacer. 38 degrees timing REAL 91 octane fuel, 9.4-1, 452 iron heads, M1, .525 comp cams solid,1-3/4" no name headers number shake out as such;
440.2hp@5171rpm 489.8ftlbs@4481rpmEngine only was using 640cfm at peak hp and pulled 690cfm 500 rpm over peak hp.
The first pulls on the motor as delivered were 380hp and 465ftlbs.At this hp level it was running 12.80's in a 3800 RR bracket car.Dave
