Vacuum secondaries vs double pumper. Marlan davis author jul 29 2019 holley type vacuum secondary carbs are more forgiving compared with mechanically actuated double pumpers.
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Vacuum secondary vs double pumper. Or in actuality lack of vacuum. If there isnt much difference ill go with the dp for the power. Discussion starter 1 may 19 2009. My wife is very sensitive to fuelexhaust smells. I drive it maybe once a week around town but bring it. 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.
I was hoping not to sacrifice too much performance. Not on a dyno. I have a 650 and an 800 avs. 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. 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. First there are no differences in the primary sides of a 750 vac secondary and a 750 double pumper holley.
I have a 750 holley vacuum secondary in my streetstrip truck. 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. Mike is right on the money. S15v8 this sport takes 2 balls. Double pumper manual secondaries. Relatively few vacuum secondary carb sizes can be made to.
Now secondaries that use vacuum to open. Vac secondarys generally get better economy and are better street carbs while the double pumper is better for the track. I am not worried about gas mileage i want performance. Would a 750 vacuum secondary be a little more friendly to her at idle and normal driving rpms. If the vs carb is more reliable much better gas mileage more driveable around town it probably would be better for me. Tuned it with a narrow band o2 sensor.
They are same and work the same and if you dont get the secondaries open will get the same mpg. Have a fairly stock 351c with holley 650 double pumper. Leaned the carb up a bit. Jump to latest follow 1 19 of 19 posts.
Gallery of Vacuum Secondary Vs Double Pumper
