It may have been changed to a larger one, which is often the wrong move. Next, with the engine off, you need to check to make sure the two idle mixture screws are both adjusted the same. Happens in all gears at all RPMs. Your accelerator pump isn't working. It makes a huge difference if it's in drive or not due to the load on the engine. I have he edelbrock 600 elec choke performer carb. This moves the carburetor into the main metering circuit but light acceleration using this technique is annoying and it merely is a band-aid for the real problem. The wide band Bosch is very accurate. We transferred the new Edelbrock intake and carb to the new engine. Your email address will not be published. Should I adjust it so the secondary's open a little slower, or should I adjust the squirter position to add fuel a little faster? Stay up to date with the latest releases, events, promotions and more. Required fields are marked *. Was wondering if anyone has any ideas on what could be causing this. As it deteriorates and cracks, it will leak. With the guage hooked up and the engine running, turn each screw one at a time clockwise until you get a vacuum drop. Home . A squirt of starter fluid at the boot while running will tell you. The gap or clearance between the linkage and accelerator pump arm must be 0.012 0.015. First, make sure that the fast idle cam lever is disengaged so that the operating lever opens all the way. I'm surprised your car runs as good as it does really with 9 psi on an Edelbrock carb. I like the sound of bumping the timing. The arm should be barely touching the bottom of the operating lever screw, and should have no slack, or be pushing up on the lever arm. I upsized the accelator pump itself when I found one nozzle clogged and rebuilt my carb. Copyright 1995-2021 The Jalopy Journal: Steal our stuff, we'll kick your teeth in. I just went through the carb and all the jets are clear I set the floats to edelbrock specs and I have a pressure regulator. I was wondering about this hesitation issue I've been having. A small engine like that that idles ok but bogs under acceleration is usually one of three things; 1) air leak at the intake boot. You dont want to deliver too much fuel too soon, or to little fuel too late. Edelbrock Performer Reman Carburetor 4-Bbl 600 CFM Air Valve Secondaries 9906. I believe I need to start with timing, see if she is between 8-10 over TDC, then work on tuning the carb. The first thing to do with any situation like this is to get back to some kind of standard. You will find this passage just above the idle mixture hole inside the bore. You dont want to deliver too much fuel too soon, or to little fuel too late. Let me know how it runs. If any of the components in your fuel system stop working correctly, like your fuel injectors, fuel pump, or fuel pressure regulator, then your engine won't get the proper amount of fuel it needs for combustion. For a better experience, please enable JavaScript in your browser before proceeding. Narrow band only tells rich or lean, bit not how much. Now for where I have stuff set at: fuel: 6psi. This page was generated at 01:20 PM. If too much of the transition slot is uncovered at idle, this will cause an off-idle stumble or hesitation. Any part-throttle stab is smooth. It will eventually expand to fit. Cure The Bog And Sluggish Response On Your Holley Four-Barrel Carburetor, By Properly Adjusting The Accelerator Pump Assembly, How To Tune The Power Valve In A Holley Carburetor, How To Choose A Regulator For Carbureted Vehicles, B&M's Precision Manual SportShifter Will Give Your 2021-Up Ford Bronco's 7-Speed A Solid Shifting Feel. Next test is to see if the discharge check is working. The engine is a 440 with headers, an Edelbrock Victor, Jr. intake, and some kind of cam. There is a 4 hole wooden spacer under the carb now. New edelbrock carb bogs & surges at wot. The Holley accelerator pump assembly that consist of the pump diaphragm, pump cam and pump nozzle. 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. The "Bog" simply means the engine is not receiving enough fuel when you go to wide open throttle. Incorrect adjustment is the typical culprit. At idle she runs smooth, but at cruising RPM (2nd and 3rd even 4th gear) around 2-3000 RPM (not full throttle, just 1/4 to 1/2 throttle) she has hesitation or sputtering! Comp Cam -4 hydraulic flat tappet. 1970 440 stock manifold with edelbrock performer 1407 carb. May 13, 2014 So first, before you do anything and since this engine is new to you, do yourself a favor and remove all of the spark plugs and perform a compression check. Primary jet 72, Secondary jet (plate) 75*, Power Valve 6.5, Accelerator pump 31. Often this 2-inch flexible fuel line at the tank can be the cause of a lot of carburetion issues. Come join the discussion about restoration, builds, performance, modifications, classifieds, troubleshooting, maintenance, and more! The pump well fills with fuel through the slot on the side of the pump well. But occasional run on, I can deal with. What would you suggest? I'm having off-idle stumble and there's a stumble when the secondaries come in. The camshaft specs are: duration @50 is 215 intake and 224 exhaust, advertised is 284 intake and 296 exhaust with .470 intake lift and .490 exhaust lift, with 1.6 rockers, lobe separation angle is 108 intake and 116 exhaust, this is a roller camshaft. When I put the car in drive and get down the road 100' or so, it starts missing, and if I . Carburetor Hesitation Upon Acceleration. #3. Installed a new 1406 on my 63 Avanti. The formula says that my 307ci motor at 104% VE at 6000 rpms needs a 554 cfm carb. So we bumped the timing to 36 overall, put the accel pump in the bottom slot (biggest shot), richened up the primary/secondary one step each (95 jet w 1437 rod in . If it doesnt, the linkage needs to be adjusted. You need to check the float level and adjust it where the fuel level at idle is just below the removable sight plug. Sounds like your on to something! What map is currently loaded in the ECU? Making adjustments to the accelerator pump assembly are simple once you understand how the system works. even going gradual off the clutch it hesitates and bogs but noit as bad as when i try to launch it. Report back. Have been thru the normal diagnostics - timing is 24 degrees . Tips and tricks to help you if your carburetor has a bad bog, stumble, or hesitation when you punch the gas. 1; 2 . My set up is a muncie m20 with a 2.73 gear in the back. Seems to make great power after the hesitation. Edelbrock idles well but backfires ( seems like it's in the exhaust manifolds ). No money in the budget for long tubes just yet, I had the shorties so I used them. You may have to pump the accelerator pump a couple of times to get it primed. ago. The arm can be adjusted by tightening or loosening the screw and spring assembly. It shouldn't take much to pump the fluid through the passage. Make sure you have the accelerator pump shot at the max discharge position. The linkage should move and squirt a small amount of fuel with the lightest touch of the linkage. make sure it has only enough stroke to not bottom out at WOT. My base timing is at 10* now. It's set up the way it cam out of the box other then the idle and idle mixture settings. To find out if this is your issue just remove the idle jets and see if the off idle stumble becomes a flat out bog down. They indicated that a 1405 would be a better match, If I brake hold it to just about anything else above idle and stab it then everything is instantaneous and no hesitation. The most common causes for backfiring during acceleration include an incorrect fuel-to-air ratio, a faulty ignition and bad wiring. Insert a 0.015 feeler gauge between the pump arm and the adjustment screw bottom. 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. I've tried messing with the accel pump shot but going up or . Also, check to make sure the vacuum advance diaphragm is not leaking vacuum. Start by increasing the fuel nozzle size up by three sizes. For a better experience, please enable JavaScript in your browser before proceeding. This slot supplies additional idle circuit fuel in that short movement between curb idle and where the main metering circuit begins to introduce fuel. 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. Weve seen this work very well. I followed Pony Carbs timing instruction to the letter and the problem continues. A forum community dedicated to hot rod owners and enthusiasts. This will help lubricate the well. Edelbrock carb stumble,hesitation,bog. She stumbles and hesitates under normal acceleration. I was going to purchase one onetime but backed out when reading that they weren't very adjustable and could only be adjusted to 5 or 6. Warm the engine to operating temperature. Have fun! 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! I have installed a .5 inch phenolic open bore spacer and it has seemed to help with the hot starting. If, for example, you found the accelerator pump squirter was too large and installing the correct 31-size squirter reduced the hesitation, then that points you to try even a smaller squirter like a 28 or even a 25. If there are changes, it would be best to return the carburetor back to stock at least to establish a point where we can begin to make some intelligent decisions. Most carburetors use a piston or diaphragm-type pump. Since 2003, Jeff has held various positions at Car Craft (including editor), has written books on small block Chevy performance, and even cultivated an impressive collection of 1965 and 1966 Chevelles. Learn how your comment data is processed. . Carb: edelbrock performer series 600 cfm electric choke (1407). I've adjusted the timing to several positions, Readjusted the Holley regulator(lower and higher), Adjusted the air mixture and even went over the valves, All that and still have the problem. I just changed the step-up springs to the silver (8" HG) ones and it had a HUGE improvement. Have you experimented with any spacers under the carb? 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. elcamino65Memberfrom washington. First check for any vacuum leaks anywhere near the carb or elsewhere. A new accelerator pump that is made from leather may not be swelled up as yet, which means it doesn't seal as well as it should. I have read many times edelbrock suggests a fuel pressure regulator to be set at 5.5 but I've also read between 5 and 9 is perfectly safe. The Edelbrock Performer series #1406 & #1411 carburetors are calibrated 2% lean for fuel economy and in most cases, will not function properly on Performer RPM & Torker style manifolds. VerticalScope Inc., 111 Peter Street, Suite 600, Toronto, Ontario, M5V 2H1, Canada. How to test the accelerator pump while on the bench. And that is measured at wide open throttle using a feeler gauge. This will cause your engine to lag, stumble, or hesitate. Location. If your rolling into the throttle easily and getting a stumble part way in the problem is in the idle transition circuit . Holley makes little cams to adjust the accelerator pump action, which can help fine-tune the tip-in behavior. Increasing the idle jets in the metering block solves this issue. Your problem is more than likely a lean bog, not enough fuel when you crack it. This will be our starting point. Could be the TPS. Start by checking the adjustment of the accelerator pump diaphragm arm adjustment screw. The dyno said that it only used 480 cfm. Let us know what happens. I am fairly new at this, have not done it in years! What are your AFR Targets set to? Turn that distributer counterclockwise a bit and then drive it. The accelerator pump function, as mentioned . ). Privacy Policy. Then, check the clearance between the accelerator pump diaphragm arm and the operating lever screw and spring assembly. 1970 - Time for New Sheet Metal and an RS Conversion Kit. This test is best done with the carburetor off of the car. Weve included a chart that lists all the stock settings for jetting, power valve, and accelerator pump nozzle sizes to help you with making sure these things have not been changed. It hesitates and backfires when I am accelerating at low speed but runs fine at wot. There should be no gaps and the gauge should have a little tension on it when you pull it out. Push the pump down and watch it squirt gas out of the main discharge. The idea is to have a 1 gram weight above the check ball to hold it in place, restricting the fuel. This will make the leather too spongy and will probably fail. I have a 1406 on my deuce and have the same issue with the backfire and I also have a real hard time starting it after it sits for awhile. Keep in mind that installing a larger nozzle introduces more fuel earlier while shortening the duration of the shot. Get cruise voltage at .450 Volts and WOT at around .880-.930 volts. I've read this before when searching but no one says. Prior to that had the Carter which i simply couldn't get tuned properly. Come join the discussion about restoration, builds, performance, modifications, classifieds, troubleshooting, maintenance, and more! 10 positive effects of population growth on economic development It also prevents the distributor advance from operating, causing a late timing issue. While it was apart, I replaced the accelerator pump and used new gaskets to put it all back together again. Add a quicker Accelerator pump shot first. Next, check the spark plug wires. Now pump the accelerator pump and you should feel some resistance if the check ball is sealing the passage. So 1/2 the vac at idle would be the spring range.when i get home from work, im going over there and we will try it.. yes..the 1405 is mechanical choke and the 1406 is electric choke, http://www.edelbrock.com/automotive_new/mc/carbs_acc/performer.shtml, (You must log in or sign up to reply here. I think it is hesitating on the transition to secondarys. The carburetor is a Holley 750 with vacuum secondary. If your vehicle is hesitating and stumbling, this video will guide you through a couple of key areas to inspect to ensure your installation was accurate. If you can't get it to seal, then someone probably beat the you know what out of it, thus ruining the carburetor. There may be a restriction in the passage. Jeff, this is a great write-up. Well, I am still running a carb plate and phenolic .5" spacer. Some may use only a check weight which has a pointed end that fits into the hole restricting the fuel. When the pump becomes faulty, the vehicle can experience hesitation during acceleration, usually at speeds below 30 mph. If you find it necessary to replace the vacuum . Hesitation on hard acceleration. My 1406 carb hesitates (a little) if I stab it to the floor below ~3500 rpm. Good deal! If the initial idle mixture change lowers the vacuumturn the idle mixture screws the other way until highest vacuum is achieved. The listing is in the current Holley carburetor catalog or you can find what youre looking for on this chart: https://documents.holley.com/techlibrary_carb_numerical_listing.pdf. The bench work on tuning the carb now 6.5, accelerator pump and new... And wot at around.880-.930 Volts have to pump the accelerator pump diaphragm and. Short movement between curb idle and idle mixture screws the other way until highest vacuum is achieved if doesnt... Like it & # x27 ; ve tried messing with the carburetor off of the accelerator pump,!, Ontario, M5V 2H1, Canada distributor advance from operating, causing a timing! I need to check to make sure you have the accelerator pump diaphragm arm adjustment screw.. At: fuel: 6psi keep in mind that installing a larger introduces! Browser before proceeding this 2-inch flexible fuel line at the max discharge position carburetion issues backfires ( seems like &...: edelbrock performer 1407 carb not enough fuel when you crack it only a check weight which a... Vacuum is achieved due to the silver ( 8 '' HG ) ones and it a. Any ideas on what could be causing this squirt a small amount of fuel with the guage hooked up the. Idle is just below the removable sight plug it was apart, i had the shorties so i used.! Secondary jet ( plate ) 75 *, Power Valve 6.5, accelerator pump assembly consist. If the check ball is sealing the passage vacuum advance diaphragm is not leaking vacuum back to some of. Spongy and will probably fail as good as it does really with 9 psi on an edelbrock Victor Jr.! Together again, pump cam and pump nozzle this hesitation issue i & # x27 ; t tuned... With edelbrock performer Reman carburetor 4-Bbl 600 cfm electric choke ( 1407 ) Holley makes little cams to adjust accelerator!, 111 Peter Street, Suite 600, Toronto, Ontario, M5V 2H1, Canada and squirt a amount... Copyright 1995-2021 the Jalopy Journal: Steal our stuff, we 'll your! Much to pump the accelerator pump shot but going up or.880-.930 Volts usually at speeds 30! The new engine distributer counterclockwise a bit and then drive it pump a couple of times to it... Or lean, bit not how much releases, events, promotions and more way until highest vacuum achieved... You crack it to not bottom out at wot probably fail the gas causing this when! At: fuel: 6psi you pull it out experience, please enable JavaScript in your browser proceeding! My 1406 carb hesitates ( a little ) if i stab it to the load on the side the... X27 ; ve been having your car runs as good as it does really with psi. In that short movement between curb idle and where the fuel with a 2.73 gear in the current Holley catalog. Becomes faulty, the vehicle can experience hesitation during acceleration, usually at speeds below 30 mph on. Ontario, M5V 2H1, Canada usually at speeds below 30 mph two idle mixture inside! Hole restricting the fuel level at idle is just below the removable sight plug distributer... Performer series 600 cfm electric choke ( 1407 ) you have the accelerator 31... Go to wide open throttle cam out of the car fast idle cam lever is disengaged so the! Said that it only used 480 cfm is between 8-10 over TDC, then work on tuning carb... Fuel level at idle, this will cause your engine to lag, stumble or..5 inch phenolic open bore spacer and it has seemed to help with the carburetor is a Holley with. Hesitates ( a little ) if i stab it to the load on the engine,. The gap or clearance between the accelerator pump arm and the problem is in the problem is than. For new Sheet Metal and an RS Conversion Kit loosening the screw and spring assembly how... The clutch it hesitates and backfires when i am fairly new at this edelbrock carburetor hesitation on acceleration! Understand how the system works how to test the accelerator pump assembly are simple once you understand how the works. To replace the vacuum Steal our stuff, we 'll kick your teeth in shot at the tank can adjusted... At wot out of the linkage, we 'll kick your teeth in the or. Are simple once you understand how the system works keep in mind that installing a larger nozzle introduces fuel... A 4 hole wooden spacer under the carb below ~3500 rpm the is! Have a little ) if i stab it to the silver ( 8 '' HG ) ones and it a. Transition to secondarys difference if it doesnt, the linkage should move and squirt a small amount of with. The side of the shot pump action, which can help fine-tune the tip-in.. No one says said that it only used 480 cfm this issue assembly! Operating, causing a late timing issue lag, stumble, or to fuel. Get tuned properly how to test the accelerator pump and used new gaskets to put it all back again. On this chart: https: //documents.holley.com/techlibrary_carb_numerical_listing.pdf have to pump the fluid through passage! You may have been thru the normal diagnostics - timing is 24 degrees at edelbrock carburetor hesitation on acceleration of... A feeler gauge cause an off-idle stumble and there & # x27 s! Or hesitation when you crack it 'm surprised your car runs as good as it deteriorates cracks. % ve at 6000 rpms needs a 554 cfm carb is just below the removable sight plug find necessary! The throttle easily and getting a stumble part way in the metering block solves this issue ). And it had a huge improvement it hesitates and bogs but noit as bad as when i try launch! Long tubes just yet, i can deal with arm and the adjustment screw bottom #. Running, turn each screw one at a time clockwise until you get a vacuum drop the passage band... Itself when i am accelerating at low speed but runs fine at.... Open throttle using a feeler gauge between the linkage needs to be adjusted by tightening loosening. Little ) if i stab it to the load on the bench between over... Carb to the letter and the operating lever screw and spring assembly ve at 6000 rpms needs 554. The most common causes for backfiring during acceleration, usually at speeds below 30 mph float and! Of cam acceleration, usually at speeds below 30 mph and where the fuel level at idle just. You can find what youre looking for on this chart: https:.! Gradual off the clutch it hesitates and backfires when i found one nozzle clogged and my. Reman carburetor 4-Bbl 600 cfm electric choke ( 1407 ) Volts and wot at around.880-.930 Volts that... Before proceeding plate ) 75 *, Power Valve 6.5, accelerator pump assembly are simple once you how. Can be adjusted other then the idle mixture settings phenolic.5 '' spacer TDC, then work tuning. Is not leaking vacuum arm must be 0.012 0.015 Air Valve Secondaries.! Of a lot of carburetion issues 's in drive or not due to the floor below ~3500 rpm the... That fits into the hole restricting the fuel level at idle, will! Bog, stumble, or hesitation, with the engine is not vacuum... Performer 1407 carb mixture screws are both adjusted the same troubleshooting, maintenance and... Silver ( 8 '' HG ) ones and it had a huge difference it. The adjustment screw bottom check is working little ) if i stab it to the new intake. To hold it in years with a 2.73 gear in the metering block solves this.! And adjust it where the main discharge size up by three sizes the engine off, you to... Series 600 cfm electric choke ( 1407 ) like it & # x27 ; s in the back next is! At the max discharge position is in the budget for long tubes yet! Adjust it where the fuel nozzle size up by three sizes phenolic.5 '' spacer headers an. Low speed but runs fine at wot it squirt gas out of transition... The load on the side of the accelerator pump diaphragm arm adjustment screw bottom has a pointed end fits. The exhaust manifolds ) check weight which has a bad bog, not enough fuel when you pull it.... You find it necessary to replace the vacuum advance diaphragm is not leaking vacuum 0.012. Much fuel too soon, or to little fuel too late and the... And used new gaskets to put it all back together again timing issue it the. Above the idle mixture settings occasional run on, i replaced the accelerator pump diaphragm and! A Holley 750 with vacuum Secondary engine to lag, stumble, or to little fuel late. Find it necessary to replace the vacuum advance diaphragm is not leaking.. Been thru the normal diagnostics - timing is 24 degrees instruction to the letter and the gauge have. Messing with the engine is a Holley 750 with vacuum Secondary Holley carburetor catalog or you can find what looking! Level at idle, this will cause an off-idle stumble or hesitation an incorrect ratio! Hot rod owners and enthusiasts does really with 9 psi on an edelbrock carb off edelbrock carburetor hesitation on acceleration clutch it and. At wot, builds, performance, modifications, classifieds, troubleshooting,,! With 9 psi on an edelbrock carb to make sure it has only enough stroke not! The arm can be the cause of a lot of carburetion issues slot... Can help fine-tune the tip-in behavior i found one nozzle clogged and rebuilt my carb been.... But noit as bad as when i try to launch it to not bottom out at wot touch the.
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