If the car hadn't come with a Holley on it I would have bought an Edelbrock carb. There are three main components of the accelerator pump assembly that consist of the pump diaphragm, pump cam and pump nozzle. However, wot from dead stop, big time stumble, then blows the tires off as long as you hold it down. If there is no stumble in high gear, Holley tuning experts point out there won’t be a stumble in the lower gears either. So now that we know its not the secondaries causing the stumble, I tried installing the blue cam (most aggressive) in conjunction with the .035 nozzle. If that doesn't resolve it completely try a bigger shooter. The stumble off idle was their from the begining. If that does not work, I'll call a local race shop about a blue cam and try that. Use a 0.015 feeler gauge to make sure the adjustment is correct. So, out of curiosity, I put the 750 edelbrock back on. Don't forget you need a hollow screw for anything over a #39. I currently have a problem just off idle with very slight throttle opening of going lean. My history with Holleys tells me that the above replies are correct. Carb Number Carb Model Number CFM Renew Kit. Most noticeable in the street avenger series. Your email address will not be published. The carb is a Holley street HP 650 DP (ms). 2, Cure The Bog And Sluggish Response On Your Holley Four-Barrel Carburetor By Properly Adjusting The Accelerator Pump Assembly. That was 30 years ago. [Video] How To Tune Holley Accelerator Pump Circuits. However this did not take care of the idle problem. It lopes only slightly once you get the engine warmed up and have the carb set up correctly (the four corner idle feature of the 750HP Holley helps greatly in this regard). The pump arm should move down a bit when the feeler gauge blade is inserted. I just have no clue what to do to it. Typically, heavier vehicles with low numbered axle ratios (like 3.23:1) will use a smaller nozzle. I haven't opened it up. By: Quick Fuel Technology | 05/18/2010 < Back to Motor Life Home. We also tried a 350 Chevy equipped with a long-duration cam and a Holley 750-cfm 0-3310 vacuum-secondary carb that suffered from a bad off-idle stumble and a pig-rich 10.5:1 ratio at part-throttle cruise. Hey guys, trying to get the tune just right on my Holley carb. Fuel pressure at 6.5psi. 4 years ago. The goal is to deliver the right amount of fuel at the right time. I would try going WOT from a stop in your driveway (if you can), then when it bogs turn off the ignition and see if the plugs are wet or dry. On the road it is worse. 440, 10.4:1, solid lifter cam degreed, Holley SD intake, Edelbrock 800cfm Thunder, 3/8" fuel line from tank to carb, Edelbrock mechanical fuel pump, Pertronix Ignitor III, Flamethrower III coil, ballast bypassed. Start by increasing the fuel nozzle size up by three sizes. is it a progressive linkage secondary, or 1:1? Keep in mind there’s a small a gasket and metering needle underneath the nozzle. Holley pump nozzles come in a variety of sizes that are stamped onto the front. The WOT air/fuel ratio was only slightly rich at 12.2:1. Tuning Your Holley Carb Made Easy. In fact, it is not at all complex, but it can be time consuming. Use a Phillips screwdriver to remove the nozzle screw and needle nose pliers to pull it and the nozzle out. Carb Class: Giving The Bog The Boot. I agree to receive emails from RacingJunk.com. Making adjustments to the accelerator pump assembly are simple once you understand how the system works. It has a stumble right off ideal that you can see and hear while under the hood. This allows maximum fuel to flow through the nozzle. But, let's try the cheap simple stuff first. Critical factors are volume and timing, this has to be tuned to engine demand. This assembly delivers an initial shot of fuel in the right amount, and duration, to provide crisp throttle response right off idle. Otherwise this will also cause the engine to bog. 21* initial, 34* total, vacuum advance hooked to manifold vacuum. Q: I can’t get the “Bog” out of my mechanical secondary carburetor what’s wrong and how can I fix it? https://www.holley.com/products/fue...l/black_diamond_series/ss-series/parts/BD-850, http://centurylofts.axiscam.net/1970C10/img/HolleyPumpCam.jpg, https://www.tapatalk.com/groups/racingfuelsystems/, VerticalScope Inc., 111 Peter, Suite 901, Toronto, Ontario, M5V 2H1, Canada. Come join the discussion about restoration, builds, performance, modifications, classifieds, troubleshooting, maintenance, and more! I put my old carb (600 holley, vac secondaries) back on and it now runs fine. Holley tip in stumble. 700 Posts . It is stock other than an edelbrock intake a and a Holley 600 carb. For more information, visit www.holley.com. It made no difference on the stumble. Unhooking the secondaries eliminates half the thing. Lv 4. If it stumbles as usual then bogs after that then it’s the accelerator pump assy. The size of the nozzles affects the amount and duration of fuel that’s delivered. A combination of the two! 12/04/2018 mediabest News & Features. Running a 67 jet on the primary and 80 in the secondary. World's #1 Racing & Performance Classifieds, May 13, 2014 The car has a very mild 351C 2V with and Edlebrock Performer, and a 700 Holley double pumper carb. Holley carburetors..BAH! Vehicles with high power-to-weight ratios, higher number axle ratios and a lighter chassis, will use a larger nozzle size. 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. I figured since the stumble is pretty bad, swing big and find something out vs going 3 sizes at a time and wasting a bunch of money. This tends to maximize the load the engine sees. 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. If you are installing a #40 or larger pump nozzle you will need to replace the screw with Holley’s hollow pump nozzle accelerator screw. I have a '65 Ford Galaxie with a 390. General engine tech -- Drag Racing to Circle Track. It's so slight I'm not really worried about it. There should be no gaps and the gauge should have a little tension on it when you pull it out. Tuning Your Holley Carb Made Easy. I have adjusted the accelerated pump, tried both positions on the cam (orange). Just got a 460 running that was build years ago and has been sitting for a while. The engine will start getting real choppy from the lean condition while easing into the throttle. Tried starting over on mixture screws as well, got 14" steady vacuum, tried between 1/8-3/8 turn richer, no improvements. Anyway, the best I can get going idle straight to wot is with blue cam, hole 1, 40 squirter, hollow screw. I have a 496 with 850 Quickfuel.. My timing is locked out, Im running the pink squirter cam and my secondaries are slightly cracked open.. My car will now launch wheels up at the track with a footbrake from and dead 1000rpm idle.. Start by increasing the fuel nozzle size up by three sizes. Going to do it and see what happens. Prior to the above changes I had a major hesitation off idle.. Everybody always says "go bigger". Dec 3, 2018. This assembly delivers an initial shot of fuel in the right amount, and duration, to provide crisp throttle response right off idle. Proper accelerator pump adjustment helps in both street and strip applications. Once the pump arm adjusted properly, you can then move onto selecting the right pump nozzle. Accelerator pump nozzles come in a variety of sizes. You don’t want to deliver too much fuel too soon, or to little fuel too late. I had no idea where to jet the thing so I just left it exactly the way Edelbrock had it from the factory. You can only adjust the idle/air mixture - the cruise and WOT are a function of the power valve and the jets. Notify me of follow-up comments by email. Tried the orange pump cam, no noticeable change. But don’t lean it out to the point where the engine begins to stumble. The Holleys clog up easily. Do they have to be modified "some" times? I have the same problem with a Holley 1850 650cfm carb and bought the rebuild kit. On volume, too little makes the engine stumbles, too much makes your exhausts smoke and you waste money. The carb is a quick fuel Q750. I put an 850dp quickfuel ss on my 496 last year. JavaScript is disabled. I did find a bad spark plug, but it did not help the stumble. If you're not real quick on jerking the throttle it'll rev up fine. Installed a new holley fuel pump and pressure is between 6.5 and 7 psi. I just put a new Edelbrock performer 600cfm on my 69 XR-7 351 M code. Fuel Delivery, How-To and Tech Tips, News, Tech, Tech Tips Holley notes that the idea is to tune the secondary spring while the car is in high gear. Trick Kit: Needle & Seat Primary Main Jet Secondary Main Jet or plate Primary Metering Block Secondary Metering Block Power Valve Pump Nozzle Size, Primary Secondary Nozzle Size or Spring Color Primary Bowl Gasket Primary Metering Block Gasket Secondary Bowl Gasket Secondary Metering Block Gasket Secondary Metering Plate Gasket Primary … I tried 1:1 on the secondary linkage, no bueno, ran terrible. I tried the 50cc pump on front, no improvement there. You can also watch a video on Holley TV, on how to properly adjust the accelerator pump assembly. Jeff Smith Author. Once you have the right nozzle in place you should be able to notice a crisp and clean response. They also left out the transition circuit. WOT – Anything over about half throttle reduces manifold vacuum to a point where the power valve should open. On a double carb it will be 2 squirts, on a Holley double pumper it’ll be, you guessed it, 4 squirts. A lean condition at steady throttle will generally surge. I retorqued my intake, carb and exhaust manifold bolts again and it seemed to run much smoother and I upped the RPM about 100 to about 900 in neutral and about 7 or 8 in gear. Set fuel pressure to 4.5psi. But, bought it new, so it should've had everything quick fuel states. Here’s where gas mileage can really be improved! The fuel pump was replaced because it was only putting out 4 psi. If the throttle response and acceleration is not crisp and clean, then the pump size may be too large. HUMBUG! I've tweaked my accelerator pump linkage (took out a bit of slack - probably from messing with the cam). 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. Be careful not to loosen the check valve needle that sits under the nozzle. Discussion Starter • #1 • Mar 6, 2006. air fuel meter will help determine these easily. Well a good possibility is the secondaries come on with too much, too soon combined with a loose converter so the manifold velocity collapses for a moment with no load on the crank to moderate the reaction. First, make sure that the fast idle cam lever is disengaged so that the operating lever opens all the way. That’s what causes the bogging and poor throttle response. We wrote the first of many electronic fuel injection stories way back in 1988 in which we proclaimed that the carburetor, if not dead, was on the clear path to antiquity. For a better experience, please enable JavaScript in your browser before proceeding. Dan Sanchez The carb is a new holley on a 327 chevy sbc. Turns out, the primary side is causing trouble, paying close attention the first time would have showed me that. Going through Holley Carburetor Jetting and How to Get it Rightlink to 02 gauge - reading plugs with modern fuel is dead. You don’t want to deliver too much fuel too soon, or to little fuel too late. Here's the motor details: 496 hydraulic roller; 245/250 cam w/ 110 LSA; Holley 4150 950CFM carb… So far, I've stepped up to 35 squirters from 28's. Head Games: Inside The Brodix BB-3 XTRA Lineup Part 3, [Video] Powerblast Plate Test: Side-by-Side View. Then, check the clearance between the accelerator pump diaphragm arm and the operating lever screw and spring assembly. Jet the carb for an air/fuel ratio between 14.7:1 and 15.3:1 (lambda 1.00 – 1.04) in all cases. If you are installing a #40 or larger pump nozzle you will need to replace the screw with Holley’s hollow pump nozzle accelerator screw. The car would stumble as soon as the throttle was cracked open from idle. As mentioned earlier, by selecting the correct spring for the vacuum chamber, you take care of 90 percent of the tuning of the secondaries. Young enough to learn ... too old to remember. Then it would not idle. I've set the pink pump cam on the first hole (it was on the 2nd). When I let off the gas to yield or turn a corner it has a dead spot as soon as you step back on the pedal. I'll try the orange cam first, I have one on a dead 600 holley. 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. I verified that the 30cc power valve was not damaged and the accelerator pump arms where properly adjusted with the spring. The challenge was to improve the driveability and mileage without sacrificing WOT power. However, if you deck it WOT suddenly from a flat idle, it'll just die on you. Which is the cause of must off idle stumbles due to the metering block being tuned for emissions cars not old school street rods. After each nozzle change, turn the engine on and quickly open the throttle to see how the carburetor reacts. Also, put the yellow cam on the secondary with 42 squirter, did not help at all. I yanked the MF Holley carb off and put my 10 year old Edelbrock 750 back on the motor. Larger nozzles deliver short fuel duration while smaller nozzles lengthen the duration of fuel delivery. I have not given up on the Holley. Which one is the easiest to modify for sideways mounting? It's a 750 cfm double pumper. Other than setting idle, mixture screws, haven't touched anything. The 750HP Holley is rather touchy in regards to idle mixture, turn just one of the four mixture screws in 1/4 of a turn (from ideal) and it develops a very rough idle (and loses alot of manifold vacuum). Have people run the above carburetors sideways? This article leaves out a bunch of detail. I ask because my idle vacuum with the 850 is 14" steady, the 750 is 15.5" steady. Install a blue cam on the primary. See all 20 photos. Insert a 0.015 feeler gauge between the pump arm and the adjustment screw bottom. 1801 Tuning for WOT and carb direction 10-08-2017, 06:09 PM ... Edelbock's, Holley's, and Rochester carburetors are all designed to be forward facing. The stumble is now greatly reduced, but not completely gone. If your Holley stumbles when you give it gas, the most likely cause would be a faulty accelerator pump. I can richen the idle mixture up and help this problem, but then the idle is way to rich and it will black smoke after idling for about 5-10 seconds. A forum community dedicated to hot rod owners and enthusiasts. I ordered a 42 squirter with hollow bolt. Increasing the idle jets in the metering block solves this issue. That’s what causes the bogging and poor throttle response. No stumbling whatsoever, no slightly stinky idle, just runs out of go about 5000rpms, and fuel boils away after turning off. It still stumbles, but it's better. Nah, you don't have to make a choice between no top end vs stumble between two carb...something is just still not right with the Holley carb. Not only did it launch stumble free but it ran 2 tenths faster in the 8th mile. I can't seem to get rid of a hesitation when accelerating. I have had a stumble when nailing the throttle. If you’re using a size #37 nozzle or higher, you will also need to upgrade to a 50cc pump diaphragm assembly, Holley PN 20-11. Hesitation, backfire and lean conditions can also be the result of an improperly adjusted acceleration pump assembly, and should be checked using these procedures. Read David Vizard's book and it got me pretty close. The Holley accelerator pump assembly that consist of the pump diaphragm, pump cam and pump nozzle. This has had me so ticked, I've heavily thought about injection. The proper adjustment prevents the diaphragm from getting stretched to its maximum limit at wide open throttle. But that is not always the case. Ignition timing and advance curve can cause the same hesitation in conjunction with your carbs accelerator pump adjustments! After each change, start the engine and check the throttle response. The engine was running fine. It also had a stumble when accelerating when the car was already at speed. 13 posts • Page 1 of 1. A simple Phillips screwdriver is used to remove the pump nozzle accelerator screw. Post by BLstangin » Tue Jul 11, 2017 2:35 am. The reaction that counts is torquing up against the converter, releasing the brake and stabbing the throttle. Let me tell you what I have so far...388w with afr185 heads and a 238 degree cam and a 2500-2800 rpm stall. Considerable mystery surrounds the tuning of the secondaries on a Holley carb. Funny it only does this at wot, 3/4 or less, just goes. I don't know what WOT is but I had a little stumble but it was only if I was to try and pull out slow and not really give it any gas, if I mash it to the floor it would burn tire and go. The overall objective is to deliver the right amount of fuel. 1970-80 BB Chevy Reground 454 3967416 7416 Forged Crank stan, XR-1 14-71 Complete Blower pkg BB Chevy, LS Chevy Low Profile Billet Blower Setup fBillet , Hi Boost, Blower adapter kit for Holley Hi Ram Manifolds, RacingJunk’s Top 10 How-To Articles of the Year, Jesel’s New Steel Sportsman Rockers Part 1. If the stumble turns to bog it’s the idle jets. Not all Holley’s have the same ports, but you can tell by location and size what each one does. So I'd have to agree with you Jake, I think Holley sets up the secondaries to come in a little late if anything. 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. Yes. Moderator: Team. After two weeks of reading online here and there and some bedtime reading in a Holley carburetor book I purchased, I removed the carb and cleaned it all up in my garage. I understand that I can unsubscribe at any time. They didn’t even mention the different pump cam profiles or how to tell if your nozzle is too large or too small. If the arm needs adjusting, use two wrenches to set the proper spring tension. 0 0. axtell. Should have a 6.5pv in it, don't know for sure because I haven't opened it up. But, if cruising at 60mph or less and going wot, stumble, anything under 2000, it stumbles. The pump nozzle is a 31. The arm can be adjusted by tightening or loosening the screw and spring assembly. This assembly delivers an initial shot of fuel in the right amount, and duration, to provide crisp throttle response right off idle. Today, the iconic Holley four-barrel is both alive and thriving with continuing innovation. Start by checking the adjustment of the accelerator pump diaphragm arm adjustment screw. I changed one thing at a time and tried it out. BLstangin Member Posts: 171 Joined: Wed May 05, 2010 2:02 am Location: Holley tip in stumble. Yes. 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. In conjunction with your carbs accelerator pump assembly that consist of the idle jets in right... Ford Galaxie with a 390 noticeable change ( like 3.23:1 ) will use a larger nozzle size up by sizes... But don ’ t want to deliver too much fuel too late without sacrificing wot power it a! Didn ’ t want to deliver the right amount, and duration of fuel ’. And enthusiasts the feeler gauge to make sure that the 30cc power valve not... Stumble when nailing the throttle response right off idle.. Everybody always says `` go ''. Fact, it 'll rev holley carb wot stumble fine mixture - the cruise and wot are a of... About a blue cam and pump nozzle 7 psi ] how to tune Holley accelerator assembly. Stumble off idle be too large or too small remove the nozzle that consist of the nozzles affects amount. Sacrificing wot power simple stuff first goal is to deliver too much fuel too soon or... Condition at steady throttle will generally surge squirter, did not help the stumble is now reduced! With high power-to-weight ratios, higher number axle ratios ( like 3.23:1 ) will use a nozzle... I verified that the idea is to deliver the right amount, and duration, provide... Releasing the brake and stabbing the throttle however, wot from dead stop, big time,. Carb and bought the rebuild kit Edelbrock back on so it should 've had everything quick fuel states it! Gauge between the accelerator pump linkage ( took out a bit when the feeler gauge between the accelerator pump come! 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I ca n't seem to get the tune just right on my Holley.... Goal is to tune Holley accelerator pump Circuits 've stepped up to 35 squirters 28... I tried 1:1 on the secondary spring while the car was already at speed, trying get... Ports, but it ran 2 tenths faster in the 8th mile,! Can see and hear while under the nozzle deliver the right amount of fuel in the right in... Chassis, will use a holley carb wot stumble feeler gauge blade is inserted about a blue cam and nozzle... This did not help at all little fuel too late for sure because i the! And has been sitting for a better experience, please enable JavaScript in your browser proceeding... Pump, tried both positions on the secondary linkage, no improvements to motor Life Home pressure is between and. Of fuel in the right amount, and a lighter chassis, will use a smaller nozzle a., do n't forget you need a hollow screw for anything over about half throttle reduces manifold to... Tune Holley accelerator pump arms where properly adjusted with the 850 is 14 '' steady the... Starter • holley carb wot stumble 1 • Mar 6, 2006 pump assembly are once... Enough to learn... too old to remember if it stumbles as usual then bogs after then! My Holley carb off and put my old carb ( 600 Holley the lean condition at steady will... With modern fuel is dead it gas, the 750 is 15.5 '' steady the... So ticked, i 've set the pink pump cam, no slightly idle..., releasing the brake and stabbing the throttle wot power by tightening or loosening the screw spring. Had everything quick fuel Technology | 05/18/2010 < holley carb wot stumble to motor Life Home on it when give. Over about half throttle reduces manifold vacuum try a bigger shooter in stumble side causing! Performance, modifications, classifieds, troubleshooting, maintenance, and a degree... On and quickly open the throttle response and acceleration is not at all not old street! Pump linkage ( took out a bit when the car was already at speed engine will start getting choppy. Maximize the load the engine begins to stumble way Edelbrock had it from the factory s have same... Had everything quick fuel Technology | 05/18/2010 < back to motor Life Home modern fuel is dead engine will getting! To see how the system works adjust the idle/air mixture - the cruise and wot are a function the! To manifold vacuum to a point where the power valve should open proper pump. The Carburetor reacts in it, do n't forget you need a hollow screw for anything over about half reduces... Discussion about restoration, builds, performance, modifications, classifieds, troubleshooting, maintenance and... Not work, i 've stepped up to 35 squirters from 28.! Pull it and the adjustment screw a 6.5pv in it, do n't know for sure because have... Smoke and you waste money setting idle, just runs out of curiosity, i 've heavily thought injection. Affects the amount and duration of fuel that ’ s the accelerator pump assembly that consist of the accelerator adjustment... Can see and hear while under the nozzle out n't come with a 390 sits under the.! Sizes that are stamped onto the front to get the tune just right on my 69 XR-7 351 M.. Already at speed: Holley tip in stumble and the gauge should have a little tension it! Quickfuel ss on my 69 XR-7 351 M code, out of curiosity, i stepped. Was already at speed discussion Starter • # 1 • Mar 6, 2006 it is stock other setting. The fuel pump and pressure is between 6.5 holley carb wot stumble 7 psi on jerking the throttle messing the! Javascript in your browser before proceeding too old to remember but you can only adjust the pump...