Also after sudden acceleration it backfires more often than not. Also when I hit the gas real fast to rev the motor it sputters really bad. Thats what causes the bogging and poor throttle response. Typically, heavier vehicles with low numbered axle ratios (like 3.23:1) will use a smaller nozzle. The idea is to have a 1 gram weight above the check ball to hold it in place, restricting the fuel. This assembly delivers an initial shot of fuel in the right amount, and duration, to provide crisp throttle response right off idle. Initial is like 20, advance all in right at 3000 w 36 deg. I like the sound of bumping the timing. Im surprised he forgot to mention the power valve. Good luck, burn rubber. Required fields are marked *. If too much of the transition slot is uncovered at idle, this will cause an off-idle stumble or hesitation. The "Bog" simply means the engine is not receiving enough fuel when you go to wide open throttle. You will find this passage just above the idle mixture hole inside the bore. No fuel coming out means you have a restriction between the pump well and the main discharge. Next, check the initial timing and shoot for between 12-14 degrees of initial timing as a starting point. Well, I am still running a carb plate and phenolic .5" spacer. Use something to poke down in the discharge hole to hold down the check ball. See if that makes an improvement. Hesitation on hard acceleration. After graduating from Iowa State University with a journalism degree in 1978, he combined his two passions: cars and writing. Use a 0.015 feeler gauge to make sure the adjustment is correct. Tuning the carburetor idle quality by using a simple vacuum gauge can often result in a better setting on the idle circuit. This article leaves out a bunch of detail. It has a flat spot/hesitation before taking off. and close the primaries back to where they need to be.make sure the timing is right along with all the basic carb settings before checking the vacuum.it will probably drive ya nuts til you get it calmed down but keep trying. Keep in mind that installing a larger nozzle introduces more fuel earlier while shortening the duration of the shot. Use a 0.015 feeler gauge to make sure the adjustment is correct. A simple Phillips screwdriver is used to remove the pump nozzle accelerator screw. At normal cruising no backfiring. Please note, it may never fit tight and isn't supposed to. The Accel pump is squirting just fine, and i have adjusted to the longest pump stroke for more fuel spray. document.getElementById( "ak_js_1" ).setAttribute( "value", ( new Date() ).getTime() ); I agree to receive emails from RacingJunk.com. Its a Edelbrock 1406 model. If I accelerate with very light throttle, the motor stumbles and seems to be loading up, and I have to give it more pedal to get rid of the hesitation. If I brake hold it to just about anything else above idle and stab it then everything is instantaneous and no hesitation. Next test is to see if the discharge check is working. bikingplumber. Have fun! There should be no gaps and the gauge should have a little tension on it when you pull it out. If your rolling into the throttle easily and getting a stumble part way in the problem is in the idle transition circuit . If it is, it can cause all sorts of problems. I don't seem too have any issues except the very occasional bog if leaving from a stop very very slow. A wise tuner once said that 75 percent of all carburetor problems are really ignition related. Learn how your comment data is processed. Holley pump nozzles come in a variety of sizes that are stamped onto the front. Generally I run those at all the way in then 2.5-3 turns back out that is the standard factory setting from edelbrock, The regulator is set up at 4 1/2 lbs I know it can take more but the reg is a cheap thing so I don't believe the settings. Also it may not squirt until the pump is part way down the well. There may be a restriction in the passage. . The first thing to do with any situation like this is to get back to some kind of standard. I just don't really have any reason to stab it WOT from idle from a dead stop. For a better experience, please enable JavaScript in your browser before proceeding. Your carb should have an instruction book on how to adjust it. If I go from a stop with mid throttle, she takes off smoothly right away with . I just bought a nice 69 Dodge Charger with a 440 that I got on a really good deal because the previous owner had given up trying to make the engine run correctly. Was running beautifully untilit stuck at 3/4 throttle on the highway. Edelbrock 1468 . Start by increasing the fuel nozzle size up by three sizes. Backfires occur in engines with severe malfunctions, such as those with diverter valve issues, exhaust leaks and faulty catalytic converters. I changed it to the 0.33" one from the 0.28" that was in it. Thanks for you're input. Next, use a flashlight to inspect the accelerator pump nozzle for a stamped number. If the initial idle mixture change lowers the vacuumturn the idle mixture screws the other way until highest vacuum is achieved. They didnt even mention the different pump cam profiles or how to tell if your nozzle is too large or too small. 2023 HOLLEY PERFORMANCE PRODUCTS, INC. ALL RIGHTS RESERVED. The proper adjustment prevents the diaphragm from getting stretched to its maximum limit at wide open throttle. Your email address will not be published. The formula says that my 307ci motor at 104% VE at 6000 rpms needs a 554 cfm carb. You may have to pump the accelerator pump a couple of times to get it primed. What map is currently loaded in the ECU? Options. posted 09-08-2005 04:44 PM. Let me know how it runs. Jun 3, 2011. Engine is a 440 with 1.6 exhaust valve,torker intake,headers and a mild . Start the engine and try turning both idle mixture screws in about 1/16-turn (this is a very slight movement). The pump needs a smooth gliding surface. Vehicles with high power-to-weight ratios, higher number axle ratios and a lighter chassis, will use a larger nozzle size. document.getElementById( "ak_js_1" ).setAttribute( "value", ( new Date() ).getTime() ); This site uses Akismet to reduce spam. After all is said and done, this is too large and over-cammed an engine (seemingly) for a dopey vacuum secondary carb. Let us know what happens. Thanks so much. This is an involved process that is too long to discuss here. Its very hard to tell which way to go in these circumstances so you just have to take an educated guess. Backfiring caused by incorrect fuel-to-air ratios result from the engine . To fit the spacer, he'd have to run a really narrow aircleaner element, which is diminishing returns in his opinion. Shoot for the highest vacuum and Rpms. The distributor weights / springs are clean and tight. The fuel pump will be drawing air instead of fuel, leaning out the mixture. For more information, visit www.holley.com. All signs point to the accelerator pump, so it looks like it is time for a carb rebuild/replacement since it is the original carb. Tuning a Edelbrock AVS2 carburetor . Power valve is probably opening because that rough idle camshaft is only allowing the motor to make 4 or 5 inches of vacuum.if thats the case try a 3.5 valve if your gauge is showing 4, 4.5 if 5 on the gauge etc..theres a small Allan set screw in the bottom of the base plate to allow you to open the secondaries at idle (slightly!) On my 82 F150 truck I have always had this issue and I have been trying to resolve it since the motor was rebuilt and I cant get it resolved. Before installing a new pump, run a blunt object around the inside of the cup to break any sealant the manufacturer may have applied for shelf life. As the pump moves up to the top of the well, fuel spills over into the well under the accelerator pump. Today's gas has very little lubricant causing premature pump failure. If your vehicle only seems to hesitate in top gear, or over about 45 mph, you may have a problem with the lock-up clutches in the torque . I went down to the pink (7" HG) spring but I think the silver performed a little better and jsut put them back in. To bring the curb idle back to the ideal spot of uncovering about 0.030 of the transition slot involves drilling air bypass holes in the throttle blades. Another thing, get a vacuum guage to tune your mixture screws with. In the center of the overall grid is the number 1, which is the stock metering combination for this carb. A new leather cup type of accelerator pump will need to eventually expand. The arm can be adjusted by tightening or loosening the screw and spring assembly. Your accelerator pump isn't working. Starts right up even after hot start. While it was apart, I replaced the accelerator pump and used new gaskets to put it all back together again. No, as in driving the car on the street. Finally, with a big cam, what can often occur is that the curb idle adjustment has to be cranked open a great amount to maintain the idle speed. Set them both the same at about 1 turns counterclockwise from fully seated. While there are other issues that may cause similar reactions within the carburetor, often the problem can be traced back to the accelerator pump system. This gives a bit more fuel mixture as the engine is moving from idle to the accelerator pump circuit. You must check this with the vacuum advance disconnected. 440 stumbles off idle only briefly but just annoying enough to want it cured. When I'm driving and I quickly press the gas peddle it seems to stumble as the secondary's open. Carb: edelbrock performer series 600 cfm electric choke (1407). Add a quicker Accelerator pump shot first. Hesitation under acceleration is often the first sign of slipping transmission clutches, caused by clutch solenoid failure, bad transmission fluid or transmission oil pump, and worn-out or burned clutches. This is what I found: I had the same problem and fix it by getting a new accelerator pump part number 1470 and no more bog edelbrock carbs have a weak pump but im 100% this will fix ur problem. There should be no gaps and the gauge should have a little tension on it when you pull it out. Executing all these suggestions will be a time-consuming process and not all may contribute to improving drivability. about 3200 rpm, I can hear the secondaries starting to kick in and then it stops accelerating and alternately bogs/surges but won't accelerate unless I lift off the throttle. Come join the discussion about restoration, builds, performance, modifications, classifieds, troubleshooting, maintenance, and more! When I put the car in drive and get down the road 100' or so, it starts missing, and if I . Edelbrock Performer Reman Carburetor 4-Bbl 600 CFM Air Valve Secondaries 9906. Thats what causes the bogging and poor throttle response. I too had bog problems with my 1406. FLoat height is often set wrong from the factory and the accelerator pump thing always seems to help. Have an instruction book on how to tell if your nozzle is large... 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