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. Vac secondarys generally get better economy and are better street carbs while the double pumper is better for the track.
Holley Vs Edelbrock
Vacuum secondary vs double pumper. S15v8 this sport takes 2 balls. Double pumper manual secondaries. They are same and work the same and if you dont get the secondaries open will get the same mpg. Discussion starter 1 may 19 2009. 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. Tuned it with a narrow band o2 sensor.
If the vs carb is more reliable much better gas mileage more driveable around town it probably would be better for me. 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. My wife is very sensitive to fuelexhaust smells. I was hoping not to sacrifice too much performance. Vacuum secondaries vs double pumper. I have a 650 and an 800 avs.
If there isnt much difference ill go with the dp for the power. Relatively few vacuum secondary carb sizes can be made to. Leaned the carb up a bit. Marlan davis author jul 29 2019 holley type vacuum secondary carbs are more forgiving compared with mechanically actuated double pumpers. I am not worried about gas mileage i want performance. I drive it maybe once a week around town but bring it.
Would a 750 vacuum secondary be a little more friendly to her at idle and normal driving rpms. 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. Have a fairly stock 351c with holley 650 double pumper. Mike is right on the money.
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. Not on a dyno. Or in actuality lack of vacuum. Jump to latest follow 1 19 of 19 posts.
Gallery of Vacuum Secondary Vs Double Pumper
