the only way to buy the accelerator pump is to buy the whole rebuild kit. Qty. When the linkage is accurately set, the circuit will begin to squirt fuel from the accelerator pump very soon after the throttle is opened even a small amount. . The secondaries open and there is the slightest amount of delay as the accelerator pump richens the mixture. The most common cause of rough idle quality in engines equipped with this carburetor is an unevenly adjusted idle mixture circuit caused by incorrectly adjusted mixture screws. An accelerator pump is a component on a carburetor. When the engine fires up it should then immediately pull open about 1/16 to 1/8 of an inch via the engine vacuum and the choke pull off. When discussing Quadrajet models, the number 4 means a four-barrel carburetor . Three different styles of pump cups were used, but all Rochester Quadrajet carburetors use a 21/32" pump cup OD. 1982 . • Check for interferences at the accelerator pump linkage. They are bought typically in sets numbered from #61 (0.0390") to #80 (0.0135"). ACCELERATOR PUMP ADJUSTMENT; AIR VALVE SPRING ADJUSTMENT The Rochester Quadrajet carburetor is a two stage, four-barrel downdraft. IDLE VENT ADJUSTMENT. 455.4hp, 494hp, 514hp, and currently over 550hp. 220/230 cam, world product heads, 9.5:1 compression, etc. Using a pump that has a short duration spring and a long stem so it can be trimmed allows you to set the pump cup just a tad above the fill slot. Products [16] Item In Cart. The Inner Workings of the Quadrajet | Hemmings For Rochester Quadrajets pick up a idle mixture adjusting tool at most any part store. I rebuilt my Quadrajet this winter due to the secondaries not working properly. The TPS plug must be absent for a Q-jet carb to be used on the street without a computer, however the feedback type Q-jet can be used in race only applications by removing the metering rods and changing the size of the primary jets. • Hook up the throttle linkage and adjust for full throttle with someone depressing the gas pedal. 79silverz28 Veteran Member. I've rebuilt more Q-jets than I can remember and have never seen anything like this. The accelerator pump orifice is also plugged. Is the accelerator pump adjustable? Author Topic: Quadrajet accelerator pump problem (Read 8686 times) mikefam. For proper accelerator pump discharge (Olds engines) always use the inner lever arm position. The accelerator pump can also be used to prime the engine with fuel prior to a cold start. Skip to the end of the images gallery. Carburetor Accelerator Pump Plunger #1982 for Quadrajet. Arrow points to Dual Capacity Accelerator Pump plug; circled is where the TPS plug would be on an electronic or computer controlled Q-jet. In stock. The Edelbrock Hi-Perf Accel Pump & Spring kit. screw down the carb air horn with the two center screws. Fast Shipping. Add to Wish List. Every time the float bowl is removed and replaced, this accelerator pump adjustment should be verified. This assembly is 2.57" long. Most differences were due to minor changes in pump plunger stem lengths and compression spring heights. A ... often the problem can be traced back to the accelerator pump system. Accelerator pump assembly, New ethanol compatible 2.57" Complete accelerator pump assembly with ethanol compatible cup and garter spring. Operate the throttle linkage a few times to be sure nothing is binding. If it's not closing all the way on a cool engine, you can adjust it from the passenger side of the car. It is a shorter style assembly that is great for performance applications. 322. Acc Pumps Complete Acc. STOP HERE and turn the carb over. CALL TO ORDER 888-799-1135. The outer hole produces a leaner pump shot, and can cause a lean stumble on engines requiring a robust pump shot. REPLACING JUST ACCELERATOR PUMP IN A QUADRAJET Consequently, is the Rochester quadrajet a good carb? Figure 30—Hot Air Choke System With Front And Rear Vacuum Breaks 356 323 320 323. Install the two metering rods down into their small barrels and attach the small support arm that holds them in position. Messages: 726 Likes Received: 0. If there is any problem with the pump, then there will be a problem in the fuel mixture during acceleration. 247 Posts . Place it on the base and mate the base to the float bowl. Sep 18, 2006 #1. Hello, I went out and started my 78 el camino today. A hesitation or lag may result during this transition and influx of air. Can anyone give me some direction? Remove the idle vent valve cover from the air horn, if so equipped. SKU. For instructions any decent parts store should have a Q-Jet repair book. The carb is completely rebuilt including new throttle valve bushings and runs great. Early Rochester four. It fired up but idled high for a couple secs but just died.I tried giving it gas but it just idled high again and then died. This is when too much fuel and not enough air are present to support combustion. Some Quadrajet builders of NHRA Stock and Super Stock Quadrajets do drill a third hole for accelerator pump travel but that's just part of getting the 21/32 maximum pump travel. Skip to the beginning of the images gallery. The accelerator pump (A) sends additional fuel through a dedicated circuit to the discharge nozzle (B). • Have someone operate the gas pedal while you verify full throttle adjustment at the carburetor. I adjusted the float to specs, pulled it up about 1/8th inch higher than it was. Is there an idle mixture adjustment like on other carburetors? It is commonly found on many older vehicles that are equipped with carburetors. A Quadrajet equipped car is often distinguishable from other cars by the sound of the engine as the secondaries open. We stock complete accelerator pumps, replaceable cups and springs. Then take the reading using the method specified for your carburetor. For this purpose, the carburetor has an accelerator pump. A Quadrajet carburettor car is often distinguishable from other cars by the sound of the engine as the secondaries open. Rods / Linkage Pulloff Rod. How much horsepower can a quadrajet support? There is a moment of quiet followed by a large increase in exhaust volume, sometimes described as a 'booming' noise. Excessive priming, like an improperly adjusted choke, can cause flooding. Place the small gasket shield back on the air horn top. "We also change the accelerator pump and install a larger needle and seat," Valdez adds. $34.95. Joined: Jan 6, 2006 Location: Texas. Engine sputtering or stalling. A minor clearance at curb idle between the arm and the adjuster is acceptable. Adjust the float up or down by bending the small float support arms (tangs) on both sides, using a pair of needle nose pliers. Bend to adjust. Install the accelerator pump arm onto the rod, then position it so that a new roll pin can be pressed into the fulcrum hole. Accelerator Pump Cup: Quadrajet 21/32 - This is FLUORELASTOMER a special purpose fluorocarbon-based synthetic rubber. Close the vent valve and open the primary throttle until the vent valve arm touches the bi-metallic strip next to the valve. There is a moment of quiet followed by a large increase in exhaust volume, sometimes described as a 'booming' noise. 360. The secondaries open and there is the slightest amount of delay as the accelerator pump richens the mixture. Usually, a faulty accelerator pump will result in a momentary lean condition, which can result in rough or sluggish acceleration, and even misfires. Quadrajet Accelerator Pump; Quadrajet Adjustments; Quadrajet Choke Circuit; Quadrajet Float; Quadrajet Idle Circuit; Quadrajet Jets; Quadrajet Metering Rod; Quadrajet Needle & Seat; Quadrajet Rebuild; Quadrajet Secondary; Quadrajet Troubleshooting Correct for any Quadrajet application. BENEFITS OF BUYING DIRECT FROM EDELBROCK. Member; Posts: 224; Quadrajet accelerator pump problem « on: May 08, 2013, 08:55:24 PM » I have a poser for the group. What's the difference between square bore and spread bore? PHOTO 15 To the side of the accelerator pump bore is a metal plate and below that is the discharge check ball. Rochester Quadrajet accelerator pump catalog. Some pull-offs had an adjustment screw, while some older carburetors require the linkage to be bent to achieve the proper opening. quadrajet idle adjustment, Fast Idle Adjusting Screw B-09249 B-09251 c D. E. 320. I use a small seal puller to push the roll pin out, away from the choke housing. Incorrect adjustment is the typical culprit. It has wide chemical resistance and superior performance, especially in high temperature : 1309CP: $10.49: Availability: Check: Complete Acc. The accelerator pump is supposed to provide additional fuel needed during acceleration. The accelerator pump … Make certain that it positively closes the throttle. If the old roll pin was not removed and you’re installing a new roll pin, remove the old pin first. • Install a good throttle return spring. The “M” after that, is a style/model type. I've got a 79 z-28 with some upgrades, nothing crazy. Discussion Starter • #1 • Jan 10, 2012. Anytime the throttle is opened, there is a transition time required for the carburetor circuits to operate. FLOAT LEVEL ADJUSTMENT. Be the first to review this product. Measure the distance between the top of the choke valve wall and the top of the pump stem. Comments: There are two holes in the accelerator pump lever arm for the lever arm rod to engage into: Inner and Outer. Ethanol ready, made in the US and meets or exceeds manufactures specifications. Holley & Rochester Delayer Spring - 66-44. Also put in a new accelerator pump … After the adjustment, put your fingers on the pivot and needle and check the measurement again. After you pump the accelerator yes it should snap closed all the way. Tech Support. Check the gasket used between the float bowl and the base as you did for the air horn/float bowl unit. Jennings did mention that ethanol/alcohol will cause an AFB carb's leather accelerator pump to peel up over time. It appears that the Quadrajet has variable orifice jets controlled by the metering rods, so that suggests it might not have low-speed idle jets used in other carburetors. Transitions Via The Accelerator Pump. "One of the most important things we modify is the idle circuit. When divorced, a linkage connects the spring to the choke plate. Accelerator Pump Rod Installed in Wrong Hole in Pump Arm Results in: Off-idle stumble or hesitation. To adjust, open throttle so choke butterfly closes (when cold), connect a hand vacuum pump to vacuum choke pull off and pump it up both verifying the diaphragm is leak free and to cause the pull off to pull the linkage to the open/running position, and use a 1/4" drill bit to check the gap between the partially open choke butterfly and inside of carburetor air horn. Rochester's timeless Quadrajet four-barrel carburetor can perform with proper tuning controlled power piston used … Match the overall length and the cup size to be sure you are getting the correct accelerator pump. 425. A 1/16" punch for removing the accelerator pump arm roll pin An adjustable T-square for setting float level A "pin vice" and a set of small numbered drill bits for measuring and making (or enlarging) small diameter holes. Quadrajet adjustment for accelerator pump. In Stock. quadrajet adjustment help - backfiring/popping Discussion in 'Troubleshooting & Diagnosis' started by 79silverz28, Sep 18, 2006. The tool bends which will make adjusting easier. PHOTO 11 To make the adjustment, connect a hand-held vacuum pump to the choke pull-off and pump it up to 18 to 21 inches of mercury. The idle screws on a Rochester Quadrajet carburetor fine tune the air-fuel ratio going into the engine during idle. Numbered bits are also available larger than #61- all the way to #1 (0.2280"). Most performance enthusiasts shun the Quadrajet … He also drills the accelerator pump discharge holes in the carb lid from 0.026 to 0.029 inch. Rochester Products produced many different varieties of accelerator pumps for the Quadrajet carburetor. Linkage to be sure nothing is binding installing a new accelerator pump is a metal plate and that. Stage, four-barrel downdraft remember and have never seen anything like this is too! 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