This Carb was originally a 650 Holley DP.For years and years of tuning I got nothing but instant fouled carbon spark plugs.I must have gone through 100 sets.I finally went to a local speed shop and the owner told me that the Carb was to small for my Chevy 402 BB.So I gave it to him and he sent it to a company in Texas.They made it flow 780cfm's and put in a 4 corner idling circuit.Finally after all those years of looking at carbon fouled plugs it fixed that problem.The problem now is with Idling.Its a very touchy carb and if I set the Carb to Idle at 1000Rpm's as the engine gets hotter the Idling Rpm's starts to climb to around 1500RPM'S.I have heard that the Double Pumper Holley is not all that good for the street.I do have a healthy sized Cam in it.I have a 4 speed Muncie also.Duration At .050 is 248 and 248,595 lift on intake and exhaust.I am only going to be driving this car on the street and Im wondering if these Holley Double Pumper Carb's suck on the street??