Hi all .... I wonder if anyone will be able to help me. I have had a 650 d/p Speed Demon on my mustang for the past 3 years ... recently the gas mileage went to double what is was (using twice as much gas !!) and the plugs were fouling up. I took it off and stuck a Holley on which has been fine for the last 6 mths. or so. Today I stripped the carb, thoroghly cleaned it, rejetted it to 68 primary and 76 secondary, put a new 4.5 power valve and reassembled with new gaskets .... the only thing now is the car started but ran like cr@p ... lots of smoke out the back and sounding like it was on 6 or 7 cylinders ... the back float level was a bit high so I adjusted that and also raised the front as that looked a little low .... no better. When I looked at the gas level in the front when the engine was stopped, I could see it dropping and hear gas running/dripping down into the intake manifold .... I thought it must be the power valve so I replaced it with a new 8.5 ... everything else looked OK in there .. put it back together .... exactly the same .... anyone any ideas ??