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