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