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Quadrajet Carburetors
Pontiac V8 Quadrajet Carburetors
Spread Bore Done Right — Quadrajet Carburetors for Pontiac V8s
The Rochester Quadrajet is the carburetor most Pontiacs left the factory with, and there is a good reason people keep them: small primaries for a clean idle and real part-throttle economy, enormous secondaries for when you ask. A worn one is a different animal — leak-down through the main body casting plug and vacuum leaks at the primary throttle shaft are the two classic complaints.
Butler carries new-casting 800 CFM Quadrajets for Pontiac 350-455 along with the 5/8-18 inverted flare fittings, ARP carb studs and stainless fastener kits a Q-jet swap actually needs.
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1. What a Properly Built Q-jet Involves
A rebuilt Q-jet and a built Q-jet are not the same thing. Whether you buy one or send a core out, this is the work list that separates them.
| Epoxied casting plug | the main body casting plug is sealed with epoxy to eliminate the leak-down that makes a tired Quadrajet flood on a hot restart. The single most valuable step on an old core. |
| Bushed throttle shafts | bushings in the baseplate to kill the vacuum leak at the worn primary throttle shaft, with the baseplate surfaced for flatness. |
| APT | an adjustable part throttle circuit, so cruise mixture in the roughly 1800-4000 rpm steady-throttle range can be trimmed in seconds with the engine running and nothing taken apart. |
| Composite float | a solid Nitrophyl float that cannot crack or sink, plus a high flow .130 inch needle and seat, new jets and metering rods, and an accelerator pump built to resist alcohol and current pump-fuel additives. |
2. Linkage, Fittings and the Details That Bite
| Late body, early car | replacement Quadrajets use later-model bodies with later-model linkage and an electric choke, so an older application may need the throttle cable adapted or upgraded. A supplied bracket set up for a 2004R is a matter of readjusting a TH350 kickdown cable; a TH400 does not use one. |
| Fuel inlet | the Pontiac Q-jet inlet is 5/8-18 inverted flare, and Butler stocks the adapter to 3/8 hose barb and the Russell adapter to -6AN. Note that some new castings put the inlet on the passenger side rather than the OEM Pontiac front position. |
| Fasteners | a Q-jet needs its own stud lengths — ARP's kit is 5/16 inch in 1.700 and 4.400 inch, set of four — or Butler's stainless eight-piece grade 5 fastener kit. |
| Flange | Q-jets are spread bore, but Edelbrock Performer and Performer RPM Pontiac manifolds and Butler's Hurricane and Crosswind carry a dual flange that takes either a Q-jet or a Holley 4150. |
If you are not sure a core is worth building, call or bring it by the shop in Lawrenceburg before you buy a kit. A cracked casting or a badly worn baseplate changes the math.
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.