I was hoping not to sacrifice too much performance. Discussion starter 1 may 19 2009.
Hughes Engines
Double pumper vs vacuum secondary. If there isnt much difference ill go with the dp for the power. I am not worried about gas mileage i want performance. First there are no differences in the primary sides of a 750 vac secondary and a 750 double pumper holley. I drive it maybe once a week around town but bring it. Now secondaries that use vacuum to open. Leaned the carb up a bit.
My wife is very sensitive to fuelexhaust smells. They are same and work the same and if you dont get the secondaries open will get the same mpg. In my experience the double pumper can make for significantly more low speed torque at the expense of fuel economy. In summary mechanical secondary carbs are much more sensitive to engine size drivetrain gearing vehicle weight and rpm range compared with the controlled secondary configuration which is why. S15v8 this sport takes 2 balls. This is primarily a street car i know that the double pumpers are worth about 10 hp over the vacuum secondary but how is drivability.
Have a fairly stock 351c with holley 650 double pumper. Would a 750 vacuum secondary be a little more friendly to her at idle and normal driving rpms. Alot of times a vacuum secondary set up has a cleaner launch and they find their way on to a surprising number of bracket racing style set ups. Relatively few vacuum secondary carb sizes can be made to work on a wide variety of. Not on a dyno. As long as you dont actuate the secondaries it uses no more fuel than a vacuum carb with the same size primary throttle bores booster type jetting and idle mixture.
Jump to latest follow 1 19 of 19 posts. I have a 750 holley vacuum secondary in my streetstrip truck. If the vs carb is more reliable much better gas mileage more driveable around town it probably would be better for me. Vacuum secondaries vs double pumper. Or in actuality lack of vacuum. Holley type vacuum secondary carbs are more forgiving compared with mechanically actuated double pumpers.
Ps your friends 351c set with the 750 vac sec versus the double pumper why was he expecting a decrease in et in just going to a double pumper design carb. Tuned it with a narrow band o2 sensor.
Gallery of Double Pumper Vs Vacuum Secondary
