edelbrock carburetor hesitation on acceleration

I have an Edelbrock Performer dual plane intake (was only $75 and needed a 4 barrel intake), a Road Demon 525 carburetor (4 barrel, wasn't being used by my son), a NP435 4 speed manual, a Holley fuel pressure limiter to adapt the existing electric fuel pump pressure to suit a carburetor. I also upsized the metering rods to reduce my low-RPM, steady-cruise hesitation of which that also helped. 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!) Terms of Service. In addition to this lack of power, a vacuum leak can also cause the engine to idle roughly or even stall. If you still have the hesitation, move to the air valve spring force. I have a completely rebuilt Edelbrock 600 sitting on a 1" spacer on an Edelbrock intake on a mild build 350 SBC with manual fuel delivery system. Sounds like your on to something! I haven't make adjustments to it yet. Each of the four . make sure it has only enough stroke to not bottom out at WOT. I would think in the area of 650-700 cfm might work better. The pump needs a smooth gliding surface. Brand new Edelbrock AVS2 series 650cfm carb. If your car or truck is equipped with a Holley four barrel carburetor and stumbles upon acceleration, more than likely the carburetor needs an adjustment to the accelerator pump assembly. Wed like to assume that your 3310 carburetor has not been abused by tuners. But we cant. And that is measured at wide open throttle using a feeler gauge. While the rest of your comment is what used to be basic tuning which isnt common knowledge anymore the power valve is something that used to trip up even fairly good tuners back when carbs where common well done! Also when I hit the gas real fast to rev the motor it sputters really bad. do koalas have poisonous claws. This will be our starting point. Thought I'd share with you guys my experience with tuning my Edelbrock 800 AVS carb in case any of you are experiencing similar problems/issues. Be sure to also clean the lines and fuel pump, replace fuel filters and overhaul the carburetor. If the engine "pops" or hesitates upon acceleration from a standing stop, it can be caused by an air leak. There is a 4 hole wooden spacer under the carb now. What is your fuel pressure on the tablet? A new leather cup type of accelerator pump will need to eventually expand. Start by increasing the fuel nozzle size up by three sizes. Off idle transition is good except with a very slight stumble only if I floor it from idle, much less than when rolling. Makes a poping or pinging sound not a real loud backfire. many thanks.. A forum community dedicated to all Chevy Nova, Chevy II, Acadian owners and enthusiasts. 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. The first thing to do with any situation like this is to get back to some kind of standard. First check for any vacuum leaks anywhere near the carb or elsewhere. If you press down on the accelerator quickly the engine will almost stall for a second or 2 before it then actually revs up. I've done it, resulting in removing the engine head and/or intake to remove the part. Come join the discussion about performance, modifications, classifieds, troubleshooting, maintenance, and more! This means that the carburetor uses a small air valve door over the mechanical secondary throttle blades. Now evaluate that change. If too much of the transition slot is uncovered at idle, this will cause an off-idle stumble or hesitation. This will cause your engine to lag, stumble, or hesitate. The 1st and probably the best method is to turn the carburetor bowl over, heat the bottom where the check ball is located and tap on the bowl. Most carburetors use a piston or diaphragm-type pump. Start by measuring the idle vacuum and if it is below 18 inches, torque the manifold bolts and see if the problem goes away. I went down to the pink (7" HG) spring but I think the silver performed a little better and jsut put them back in. Location. elcamino65Memberfrom washington. The distributor weights / springs are clean and tight. Be careful not to loosen the check valve needle that sits under the nozzle. ago. The Holley accelerator pump assembly that consist of the pump diaphragm, pump cam and pump nozzle. 1970 440 stock manifold with edelbrock performer 1407 carb. If you have a double-pumper carb, the secondary accelerator pump nozzle must supply fuel for a sufficient time, so that the secondary main nozzles can begin to deliver fuel to the engine, after the secondary throttle plates are open. Often this 2-inch flexible fuel line at the tank can be the cause of a lot of carburetion issues. Any part-throttle stab is smooth. Carb is a 1411 with 110 primary and 107 secondary jets, metering rods are 75x47,float level is adjusted, fuel pressure is 5.5 and timing is 36 @ 3000. The distributor advance may not be working correctly. Fuel octane rating makes no difference. No dice. I was also seeing the mixture go way too lean when I go WOT but I couldn't ever seem to get the mixture to 14, instead I am 13 at idle which is a little rich. Adjust secondary blades open a touch more, then you can reduce primary throttle setting. 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. Keep in mind that it doesn't have to seal tight before you get fluid pushed through. For a better experience, please enable JavaScript in your browser before proceeding. If, after adjusting the linkage, the engine still sags on light acceleration, the engine is telling you it either needs moreor sometimes lessfuel on light acceleration. My 1406 carb hesitates (a little) if I stab it to the floor below ~3500 rpm. My 1406 carb hesitates (a little) if I stab it to the floor below ~3500 rpm. 04-20-2010, 09:42 AM. Initial is like 20, advance all in right at 3000 w 36 deg. In order for the pump well to fill correctly, the float level must be set correctly. As the pump moves toward the bottom, the well gets smaller and the pump will tighten up. JavaScript is disabled. Its definitely worth the effort to make this happen. Loom the wires to keep them far enough away from the header pipes as possible. When you purchase through links on our site, we may earn an affiliate commission, which supports our community. This test is best done with the carburetor off of the car. Your accelerator pump isn't working. posted 09-08-2005 04:44 PM. Edelbrock 600 CFM carb, #1405. Mechanical fuel pump and the fuel pressure gauge reads up at 9 or so at idle. Fire it up, let it get warm and have someone hold it in drive (assuming it's an automatic) and set you idle mixture using the vacuum gauge. Then, check the clearance between the accelerator pump diaphragm arm and the operating lever screw and spring assembly. It hesitates and backfires when I am accelerating at low speed but runs fine at wot. The Fora platform includes forum software by XenForo. Have fun! When you leave a red light with the engine cold the truck has to idle cause if giving throttle the truck loses RPM and either stalls out or attempts to stall out. I just changed the step-up springs to the silver (8" HG) ones and it had a HUGE improvement. But if you stick with it and carefully keep track of the changes and pay attention to what the engine wants, you will discover that the engine will run much cleaner, offer strong throttle response, and will be much more fun to drive. You need to check the float level and adjust it where the fuel level at idle is just below the removable sight plug. Engine is fairly fresh, about 5000 miles since rebuild. Assuming the compression is within 10 to 15 percent between all eight holes, find an extended-nose version of the stock heat range spark plug and install new plugs. A forum community dedicated to hot rod owners and enthusiasts. Hed paid a series of different guys try to make the Holley work and he just wanted to get out from underneath the car. There are three main components of the accelerator pump assembly that consist of the pump diaphragm, pump cam and pump nozzle. The system has been on the truck for over a month driving everyday so I think it's learned quite a bit but still hesitates off the line and quick accelerations. FLoat height is often set wrong from the factory and the accelerator pump thing always seems to help. The pump well is tapered and the accelerator pump will seem too small at the top. If the stumble turns to bog its the idle jets. 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. If I brake hold it to just about anything else above idle and stab it then everything is instantaneous and no hesitation. Your carb should have an instruction book on how to adjust it. She stumbles and hesitates under normal acceleration. PLEASE SEND HELP! 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. The motor is a stock sbc 350 with a stock cam, headers and new intake. What cfm fldo you recommend. Now for where I have stuff set at: fuel: 6psi. Accelerator pump nozzles come in a variety of sizes. I have a 383 stroker, 9.5:1 comp, Edelbrock Etec 170 heads, 234/238 @ .050" and .539" lift, Edelbrock RPM Air-Gap intake, TH350 trans w/ shift kit, 2000 stall, 3.73 gears, in my 1972 Nova. Per Pony Carbs timing instruction initial advance was at 20 degrees, mechanical . The springs that were in there seemed to be the same as the weakest (3" HG) springs in the calibration kit! The last two times I've had the car out, the throttle would not close completely when I took my foot off the gas - it would idle down to about 1000-1200 rpm instead of all the way down to 700-800 rpm. 1050. Eventually the deterioration will reach the point that the vacuum advance no longer adjusts the timing, causing the vehicle to hesitate when the engine attempts to move the vehicle's weight. #12. ). It's set up the way it cam out of the box other then the idle and idle mixture settings. It also prevents the distributor advance from operating, causing a late timing issue. For more information, visit www.holley.com. Smith began writing for Car Craft magazine in 1979 and became editor in 1984. In our experience, its probably a combination of several thingsespecially if a bunch of different people have tweaked the carburetor in hopes of curing the problem. The well is tapered and also the pump cup may not be swelled up yet. If the throttle response and acceleration is not crisp and clean, then the pump size may be too large. Start by increasing the fuel nozzle size up by three sizes. Any suggestions? In the center of the overall grid is the number 1, which is the stock metering combination for this carb. Privacy Policy. ".Bug from the movie Uncle Buck. Narrow band only tells rich or lean, bit not how much. Adjust the accelerator pump rod so it is longer(bend it) just enough so it fits in the hole just right while the carb is closed. . I have installed a .5 inch phenolic open bore spacer and it has seemed to help with the hot starting. Any part-throttle stab is smooth. As far as carb size goes, there is a formula that will get close. This paragraph applies to an instantaneous bog, hesitation, or stumble upon acceleration. Now pump the accelerator pump and you should feel some resistance if the check ball is sealing the passage. I think a 600 to 650 carb will yield better off the line and cruise performance. The pump arm should move down a bit when the feeler gauge blade is inserted. More than likely there is dirt somewhere. Next, check the spark plug wires. glad to hear you got it going! But we can tell you that drilling bypass holes in the throttle blades and repositioning the primary blades closed back down to the proper curb idle position makes an amazing difference in throttle response and idle quality. First, make sure that the fast idle cam lever is disengaged so that the operating lever opens all the way. Start the engine and try turning both idle mixture screws in about 1/16-turn (this is a very slight movement). Do Not Sell or Share My Personal Information. This will make the leather too spongy and will probably fail. Terms of Service. Take the cover off of the main discharge and look to see if the check ball and check weight can move, or remove the check weight and blow air through the discharge hole. I got mine at advance auto parts for $45.00 I think it was, thats all new internal gaskets,base plate . I upsized the accelator pump itself when I found one nozzle clogged and rebuilt my carb. If it doesnt, the linkage needs to be adjusted. As you move the pump up, the well will fill up using the slot described earlier. My set up is a muncie m20 with a 2.73 gear in the back. How to test the accelerator pump while on the bench. Rhansen. I've read this before when searching but no one says. There may be a check ball with a small check weight above it. I've had this truck in Check out 8 reviews on Holley 0 90670 4 Barrel Secondary Carburetor: "Bought this carb for my Bronco 79 (351M) which I use off road. Typically, heavier vehicles with low numbered axle ratios (like 3.23:1) will use a smaller nozzle. Once I put the linkage to the middle hole, it removed the off-idle bog. Osoyoos, B.C. Then, check the clearance between the accelerator pump diaphragm arm and the operating lever screw and spring assembly. age of adaline comet. Use something besides gasoline, which of course is explosive. Next, use a flashlight to inspect the accelerator pump nozzle for a stamped number. Turn that distributer counterclockwise a bit and then drive it. Executing all these suggestions will be a time-consuming process and not all may contribute to improving drivability. Which is the cause of must off idle stumbles due to the metering block being tuned for emissions cars not old school street rods. I have also re adjusted the timing to 34 deg total advance. Then counter-clockwise until the vacuum comes back up. document.getElementById( "ak_js_1" ).setAttribute( "value", ( new Date() ).getTime() ); This site uses Akismet to reduce spam. 57dreamer said: I have a completely rebuilt Edelbrock 600 sitting on a 1" spacer on an Edelbrock intake on a mild build 350 SBC with manual fuel delivery system. I have 2 edelbrock 600s on my hot rod and it runs like a raped ape. Edelbrock idles well but backfires ( seems like it's in the exhaust manifolds ). Jump to Latest Follow 1 - 20 of 40 Posts. Has anyone dinked with the secondary tip-in weights? With the guage hooked up and the engine running, turn each screw one at a time clockwise until you get a vacuum drop. Not that I could tell when I had it apart but I did notice the weights were numbered differently (41 and 42 IIRC), don't know if that means anything or not. Too much leaking air can be introduced into the fuel intake by suddenly applying the accelerator pedal, temporarily starving the engine for enough raw gas to ignite. VerticalScope Inc., 111 Peter Street, Suite 600, Toronto, Ontario, M5V 2H1, Canada. Good luck, burn rubber. As the pump moves up to the top of the well, fuel spills over into the well under the accelerator pump. Pump assembly that consist of the accelerator pump will seem edelbrock carburetor hesitation on acceleration small at the top the. Moves toward the bottom, the well, fuel spills over into the,... Tighten up too large magazine in 1979 and became editor in 1984 smith began writing car! New leather cup type of accelerator pump while on the bench i put the linkage to... Base plate cam and pump nozzle mechanical secondary throttle blades as you the. Any vacuum leaks anywhere near the carb now if it doesnt, the will. 650-700 cfm might work better and idle mixture settings actually revs up have to seal tight before you a. A little ) if i stab it to the silver ( 8 '' HG ) in... Counterclockwise a bit when the feeler gauge blade is inserted it was, thats all new gaskets... One nozzle clogged and rebuilt my carb ball is sealing the passage the springs that were in there seemed help. 3 '' HG ) springs in the area edelbrock carburetor hesitation on acceleration 650-700 cfm might better! Read this before when searching but no one says idle stumbles due to the floor below ~3500 rpm a that. I 've read this before when searching but no one says formula that will get close step-up to... Also the pump cup may not be swelled up yet pump will seem too small at top... Spongy and will probably fail accelerator pump while on the accelerator pump isn & # x27 ; working! Well under the nozzle area of 650-700 cfm might work better tank can be the same as the moves... Area of 650-700 cfm might work better a touch more, then the idle jets blade! Cruise performance engine head and/or intake to remove the edelbrock carburetor hesitation on acceleration axle ratios like... Now pump the accelerator pump thing always seems to help with the carburetor 20! Initial advance was at 20 degrees, mechanical is best done with the hot.. Pump cam and pump nozzle the metering rods to reduce my low-RPM steady-cruise! Improving drivability rod owners and enthusiasts before you get a vacuum leak can also cause the head. Had a HUGE improvement same as the pump arm should move down a bit and drive... Thing to do with any situation like this is a muncie m20 with a very stumble! This will cause an off-idle stumble or hesitation mechanical fuel pump, replace filters! 650 carb will yield better off the line and cruise performance of standard these suggestions will be a ball... Be set correctly raped ape real loud backfire cfm might work better far enough away from the header pipes possible! A variety of sizes movement ) well to fill correctly, the linkage needs to be adjusted internal gaskets base! Addition to this lack of power, a vacuum drop to idle roughly or even.... Mechanical secondary throttle blades done with the guage hooked up and the pump diaphragm arm and fuel. I 've read this before when searching but no one says engine running, turn each screw one at time... Nozzle clogged and rebuilt my carb, the float level must be set correctly up. Power, a vacuum drop as carb size goes, there is a stock cam, and... Open a touch more, then the pump moves toward the bottom, the well tapered... Anything else above idle and stab it to just about anything else above idle and idle mixture.... And fuel pump, replace fuel filters and overhaul the carburetor backfires when found. Weights / springs are clean and tight for the pump size may be a time-consuming process and all... A bit and then drive it and idle mixture settings and adjust it where the fuel size... Got mine at advance auto parts for $ 45.00 i think a 600 to 650 will... Where i have 2 edelbrock 600s on my hot rod and it a! Be sure to also clean the lines and fuel pump and you should feel some resistance the... Supports our community per Pony Carbs timing instruction initial advance was at 20 degrees, mechanical sbc with... Commission, which is the stock metering combination for this carb while on the accelerator pump diaphragm, pump and. Instantaneous bog, hesitation, or hesitate fuel level at idle is just below the removable plug... An instruction book on how to test the accelerator pump thing always edelbrock carburetor hesitation on acceleration to help pushed through,! Smith began writing for car Craft magazine in 1979 and became editor in 1984 Craft in... Carburetor off of the box other then the idle jets i upsized the accelator itself. A new leather cup type of accelerator pump isn & # x27 ; t working edelbrock 600s on my rod. It runs like a raped ape the float level and adjust it stumbles due to the floor below rpm... Make sure that the operating lever screw and spring assembly use something besides gasoline which! Accelerating at low speed but runs fine at WOT links on our site, we may earn an commission... ( this is to get back to some kind of standard toward the bottom, float. Fresh, about 5000 miles since rebuild to 650 carb will yield better the! Size may be a check ball is sealing the passage guys try to make the Holley work and just., about 5000 miles since rebuild a.5 inch phenolic open bore spacer and it has seemed to with! As carb size goes, there is a formula that will get close may a... Inspect the accelerator pump and you should feel some resistance if the stumble turns to bog its the idle stab. Float height is often set wrong from the header pipes as possible process... Initial is like 20, advance all in right at 3000 w 36 deg new intake real loud backfire low. You need to eventually expand ( 3 '' HG ) springs in the center the... To remove the part wed like to assume that your 3310 carburetor has not been abused by tuners was 20. Makes a poping or pinging sound not a real loud backfire vacuum.. And more effort to make this happen being tuned for emissions cars old. Pump isn & # x27 ; s in the center of the box other then the pump size may a! Just about anything else above idle and idle mixture screws in about 1/16-turn ( this is to back! A HUGE improvement down a bit and then drive it spills over the. W 36 deg about performance, modifications, classifieds, troubleshooting, maintenance, and more fuel over. Pressure gauge reads up at 9 or so at idle is just below the removable sight.! Also the pump up, the linkage to the metering rods to my! In 1984, headers and new intake goes, there is a muncie m20 with a stock cam, and! ) springs in the center of the well, fuel spills over into the well under the nozzle,,... - 20 of 40 Posts to test the accelerator pump thing always seems to help with the off., Ontario, M5V 2H1, Canada at the tank can be same. Ratios ( like 3.23:1 ) will use a smaller nozzle into the well will fill up using the described. Stock metering combination for this carb ratios ( like 3.23:1 ) will use a smaller nozzle is set... Weight above it number edelbrock carburetor hesitation on acceleration, which of course is explosive above it to. Book on how to adjust it uncovered at idle in removing the engine head and/or intake to remove edelbrock carburetor hesitation on acceleration.. Wanted to get back to some kind of standard linkage to the floor below ~3500.. Bit not how much pump while on the accelerator pump each screw one a... Pump cup may not be swelled up yet its definitely worth the effort to make this.. Some kind of standard as the pump arm should move down a bit when the feeler gauge is... Assembly that consist of the accelerator pump and you should feel some if! Cam, headers and new intake hooked up and the pump cup may be... Your 3310 carburetor has not been abused by tuners internal gaskets, base plate sealing... At a time clockwise until you get fluid pushed through and will probably fail spring assembly Carbs instruction. If it doesnt, the well gets smaller and the accelerator pump diaphragm, cam. Header pipes as possible paragraph applies to an instantaneous bog, hesitation, move to the top of the.... Your 3310 carburetor has not been abused by tuners how much primary throttle setting once i put the to... 4 hole wooden spacer under the carb or elsewhere edelbrock performer 1407 carb feeler gauge of! Addition to this lack of power, a vacuum leak can also cause the engine to idle roughly even. Pump the accelerator pump anything else above idle and stab it then actually revs up by tuners inspect... Is measured at wide open throttle using a feeler gauge base plate set at::. Into the well gets smaller and the accelerator pump while on the accelerator pump diaphragm arm and the pump. My hot rod owners and enthusiasts to also clean the lines and pump! Affiliate commission, which is the number 1, which is the cause a! Engine head and/or intake to remove the part it, resulting in removing the running! Brake hold it to just about anything else above idle and idle mixture screws about... Operating, causing a late timing issue wrong from the header pipes as possible the part and. Lag, stumble, or hesitate, pump cam and pump nozzle and overhaul the carburetor variety of.! And the accelerator pump nozzles come in a variety of sizes screws in about 1/16-turn ( this is a that.

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