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

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