They are same and work the same and if you dont get the secondaries open will get the same mpg. Mike is right on the money.
Race Vs Street Carburetor Modern Tunability Blurs The Line
Vacuum secondary vs double pumper. If there isnt much difference ill go with the dp for the power. Vac secondarys generally get better economy and are better street carbs while the double pumper is better for the track. Vacuum secondaries vs double pumper. Jump to latest follow 1 19 of 19 posts. Relatively few vacuum secondary carb sizes can be made to. I have a 750 holley vacuum secondary in my streetstrip truck.
Now secondaries that use vacuum to open. First there are no differences in the primary sides of a 750 vac secondary and a 750 double pumper holley. I was hoping not to sacrifice too much performance. Would a 750 vacuum secondary be a little more friendly to her at idle and normal driving rpms. 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.
Tuned it with a narrow band o2 sensor. You floor it they open vaccum secondaries secondaries operated by primary venturi vacuum different from manifold vacuum it is the same as the signal that pulls fuel into the primaries it increases in proportion to air flow through the primaries. I drive it maybe once a week around town but bring it. Leaned the carb up a bit. Not on a dyno. My wife is very sensitive to fuelexhaust smells.
Thus if you are puttering around with a double pumper and stay out of the secondaries it should get the same fuel economy as a vac secondary assuming they have the same size throttle bores primary jetting and idle mixture qualities. Marlan davis author jul 29 2019 holley type vacuum secondary carbs are more forgiving compared with mechanically actuated double pumpers. Discussion starter 1 may 19 2009. I am not worried about gas mileage i want performance. Double pumper manual secondaries. If the vs carb is more reliable much better gas mileage more driveable around town it probably would be better for me.
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. Or in actuality lack of vacuum. I have a 650 and an 800 avs.
Gallery of Vacuum Secondary Vs Double Pumper
