[Jmar]

Hi David!

I had a problem similar to what you described while using a 750 DP on my car. From what I understand, Holley DPs are meant to run rich since they are tuned more
for racing. My car ran rich on the dyno so I followed the advice of the dyno man and leaned it out.

The stumble ocurred during part throttle after I leaned the carb out. The more I leaned it out the better it performed on the top end, but it stumbled more during the transition from part throttle to the power mode. There are two things that I did to help eliminate the "hole".

1) I changed the settings from stock to position 2 on my accelerator pump cams. This improved throttle response by moving the cams to a more agressive curve. It is also free!! Usually high volume pumps aren't required and may cause various clearance problems (eg you may need a carb spacer to clear the larger pumps and then what happens to hood clearance, linkage, etc ?).

2) I went to a power valve that opened under slightly higher vacuum since my cam is fairly mild. This require that you drive the car with a vacuum gague.

As I have learned from reading and talking to other tuners, my carb may be too big for my engine to have perfect street manners. So the things that I mentioned above help to cover up the problem. I may buy a 650DP to see if throttle response improves and ETs go down at the strip.