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Double Pumper
Pontiac V8 Double Pumper
Mechanical Secondaries — Double Pumper for Pontiac V8s
The Holley Double Pumper is defined by two things: mechanical secondaries that open with the throttle linkage, and a second accelerator pump on the secondary side to cover the fuel demand when they do. That is what makes it snap, and it is also why it is fussy about what is behind it.
Butler stocks the classic zinc-body 4150 Double Pumpers in 700, 750 and 850 CFM, the aluminum Ultra Double Pumper in 850, and Holley's USA-built Brawler Street mechanical secondary carburetors in 750 and 850.
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1. What the Second Pump Is Actually For
On a vacuum secondary carburetor the secondaries open when the engine asks. On a Double Pumper they open when you do — and an engine that is not ready for that much throttle area goes flat for a beat before it recovers. The secondary accelerator pump exists to cover that gap with fuel until airflow catches up.
2. Classic, Ultra or Brawler
All three are 4150 mechanical secondary carburetors. What separates them is body material, choke and how deep the tuning goes.
| Classic Double Pumper | zinc body, gold dichromate or tumble polished finish, manual cable-operated choke, dual accelerator pumps, dual feed fuel inlets, straight boosters. The traditional muscle car answer, stocked in 700, 750 and 850 CFM. |
| Ultra Double Pumper | all aluminum, roughly five pounds lighter than a comparable zinc carburetor, with 6061-T6 billet metering blocks and base plate, four-corner idle, a built-in clear sight glass for fuel level, down leg boosters and — a first on a Double Pumper — a factory preset electric choke. Butler stocks the 850 in Hard Core Gray, polished with blue billet and polished with red billet. |
| Brawler Street | machined and assembled in the USA with black billet metering blocks and a black billet throttle body for throttle shaft stability, electric choke, four-corner idle on the mechanical secondary models, polished bowls and main body. Butler stocks 750 and 850 CFM. |
3. Choke, Idle and Daily Manners
This is the practical fork. The classic 4778, 4779 and 4781 carburetors use a manual choke, which means a cable to the dash and a driver who knows how to use it — excellent control, more involvement. The Ultra and the Brawler both carry a preset electric choke, so a street/strip Pontiac that still gets driven cold is easier to live with.
4. What Has to Go With It
| Dual feed fuel line | every Double Pumper has two inlets. Butler stocks Holley and Russell dual inlet kits for 4150 bowls with 7/8-20 threads, with or without a fuel pressure gauge port. |
| Throttle and kickdown | these are compatible with GM, Chrysler and Ford automatic kickdown linkage, but additional parts may be required. A TV cable on a 200-4R or 700R4 is not something to improvise. |
| Air cleaner clearance | if the car wears a shaker, check drop base clearance before you order — a manual choke tower and a drop base do not always agree. |
Buy this one for the combination you actually have. A Double Pumper on the right drivetrain is one of the best-feeling carburetors ever built; on the wrong one it is just a carburetor with a flat spot.
Not sure what your Pontiac needs?
Call our tech team at 866-762-7527. Tell us your engine, heads, car, and power goal, and we will put the parts together as one combination that works.