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Holley Carburetors
Pontiac V8 Holley Carburetors
Street to Race — Holley Carburetors for Pontiac V8s
A Holley carburetor is where most Pontiac owners land once they step away from a factory Quadrajet. The 4150 and 4500 platforms are modular — metering blocks, jets, squirters, power valves and secondary springs all come apart with the carb on the engine — so one casting can be calibrated for a mild street 400 or a big-inch race engine.
Butler stocks the Holley line as a ladder: Street Avenger, Double Pumper, HP, Ultra XP and Dominator, plus Brawler Street models and the dual-feed fuel lines, studs and throttle linkage that have to go with them.
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More About Holley Carburetors
1. The Ladder, Top to Bottom
Each family below is a genuine change in behavior, not a badge on the same carburetor. Pick the rung that matches how the car is actually driven, then go to that page for sizes and detail.
| Street Avenger | vacuum secondaries, factory preset electric choke, a street calibration that works out of the box, and a fuel line kit in the box. The bolt-on end of the range. |
| Double Pumper | mechanical secondaries and dual accelerator pumps. Holley intends them for lightweight cars with a manual transmission, or an automatic with high stall and low gears. |
| HP | race calibration, no choke, screw-in air bleeds, four-corner idle and Dominator-style bowls that plumb from either side. A square-bore race carburetor. |
| Ultra XP | the HP idea rebuilt in aluminum, with bigger bowls, billet metering blocks and an integrated idle bypass valve for controlling idle behind a radical cam. |
| Dominator | the 4500 flange. Annular boosters, three-circuit metering, dual 50cc pumps, race-only calibration. |
2. Settle the Flange, the Fuel and the Hood First
Three things decide whether the carburetor you picked will actually bolt on and run.
| Flange | Avenger, Double Pumper, HP and Ultra XP are 4150 square-bore. The Dominator is 4500 and wants a 4500-flange manifold or an adapter. Butler stocks both flange styles in Northwind and Edelbrock manifolds. |
| Fuel line | a dual-feed line is not optional on these. Standard 4150 bowls with 7/8-20 threads take a normal dual inlet kit; Ultra XP bowls use -8 O-ring inlets and need the Holley XP-specific line, which is longer to clear the deeper bowls. |
| Hood and air cleaner | a Trans Am shaker or a tight hood limits carburetor height and, on some Butler drop bases, forbids a choke housing altogether. Check the air cleaner before the carburetor, not after. |
3. Sizing Without Guessing
CFM is a flow rating, not a horsepower rating. More displacement and more rpm take more airflow, but a carburetor that is too large for the combination gives up booster signal at low speed, and you feel that as soft throttle response and a lazy tip-in long before you feel the extra top end.
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.