Holley carb wot stumble. Carb was running on idle jets and transition slots.

Aug 4, 2008 · Most times you never see it. You can use Holley pump cams, so try just about any other. These carbs employ two more idle mixture screws on the secondary side of the carburetor. Holley performance carburetors are equipped with a fuel bowl that is designed either for a center pivot or a side pivot float. Jul 12, 2023 · I can clearly see the leaning out of the a/f ratio when the stumble is happening. 040 stopped the part throttle snap stumble, but didn't fix WOT. What I did was pull the accelerator pump cam and flip it around until I was getting the biggest shot possible, also adjusted the acc. Feb 19, 2011 · @ wide open throttle you should be able to push the pump lever into the dia. 015-inch of clearance between the lever arm and the pump linkage at max lift (WOT). It was mistakenly left installed after a problem causing low idle vacuum of 8-9 was found and fixed. I could take any Holley carburetor right out of the box, slap it on your engine, with the only modification needed other than basic tuning be possibly changing the power valve based on your idle vacuum signal, and it would perform better than BM described his situation. Thanks for any ideas/input! -----Original Message-----Sent: 3/16/2004 10:36:43 AM Subject: 670 Street Avenger Dear Sirs, Aug 22, 2015 · I diluted it further to 77%. May 9, 2012 · The BG carbs all came with a pink pump cam (how appropriate for Barry, what a tool) which is the least aggressive of all the cams in the early part of the throttle travel - where most engines need it most. 020 Jun 17, 2010 · carb specs: 66 jets, 31 squirter, 600cfm vacuum sec holley. On my HP series Holley 750 the factory jetting was either 72 or 74 in the primaries with . This clearance should be around . Want more in-depth information? Check this how-to-guide on Holley carburetor problems, possible causes, and corrective actions. 3:1; The advantage for the knowledgeable carb tuner is that he can perform these modifications on an affordable carburetor and get very close to the same part-throttle performance as the best EFI system. 7 but at WOT it is at 14. Gave up and bought the hollow screw, which is what was supposed to be used in a Holley carburetor with a discharge nozzle greater than 40, and low and behold the carburetor works like it is supposed to. If you have a regular carb, the air bleeds are press-in (red arrows) items, so changing them is limited to drilling larger or pulling them out and installing smaller ones. The video explains the various jet sizes, and how they affect engine performance. "The first adjustment to check is the clearance between the pump operating lever and the pump diaphragm cover's arm, at wide open throttle. Dec 31, 2015 · When Holley designed the 4150/4160 style carbs 40-50 years ago, cars makers had three things that where all basically the same. For instance, I have never seen anyone successfully use a Rochester Quadra-Jet carb on a 800 HP V8 engine drag car. 005” change in size will be a noticeable difference. A lot of times people have the throttle blades set too far open at an idle, exposing too much of the idle circuit--when you go to give it gas there is an instant lean condition that either requires TOO large of discharge nozzles, or simply cannot be corrected. This will give you a small stumble as well. Nov 3, 2015 · *Holley 4150 750 Double Pumper, model 4779 Timing all in at 36, 18 initial, 10 in the vac can. 4 AFR, cruise is 13. Mar 8, 2010 · 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. Mar 28, 2004 · Running a 30cc pump and adjusted at . Car was running great outside of a slight stumble at cruise. 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. In the end it’s Jan 10, 2011 · Though stoich is ideal for many circuits of operation, it is typically too lean at wide open throttle for the vast majority of engines and will be most happy between 12:1-13. 5 in of vac at idle Aug 26, 2016 · I tried to tune out that off idle stumble when I had time for several months thinking that Chevy had a reason for using the standard screw. Engine is a 355 4 bolt main, 10:1 flat top pistons, edelbrock aluminum intake, 2. 5 InHg at wide-open-throttle (WOT). Holley 670 street avenger vacuum secondaries. Aug 21, 2008 · I'm running a 4777 650 cfm Holley. 4 at cruising, It doesnt help going Down on main jets. 40's on pump gas and 235 radials. Most double-pumper carbs are equipped with a progressive linkage that starts opening the secondaries when the primaries are about 40 percent Sep 11, 2009 · If I have both primary and secondary throttle blades showing a bit of transfer slot, the engine may idle at several thousand rpm. If not then you need to inspect the pump diaphragm for a hole or tear. It's pretty bad, and only happens when I go to wot quickly. 2)Watch the Holley videos. This caused the engine to stumble and sometimes die when stepping on the throttle. Some cleaning and adjustments usually solve the problem. Here's my "letter" I sent to Holley and the response. In basic terms, if you want low-end torque at lower engine RPM, consider a dual-plane intake manifold. Apr 3, 2020 · However, wot from dead stop, big time stumble, then blows the tires off as long as you hold it down. Fortunately Holley’s made a kit to avoid that, a quick change kit so you can change the spring in 1 Jun 13, 2008 · Had the carb apart last night to install different jets and noticed the pv was a 4. Only after becoming aware of the transition circuit can you begin to adjust it. 0 . 015)so you dont bend anything. The cure for me was to increase the primary jets from 61 to 63. This weekend I'm installing a 50cc pump and spacer - I'll let you know if it helps. 015" just so it is not bottomed out at wide open throttle also For the power valve size you will need to check your engine vacuum @ idle ( in gear if auto trans ) May 1, 2020 · - Sent data log to Holley. FLOODING (OVERFLOWING) Fuel overflowing from the carburetor may be caused by a number of issues: (1) Float/fuel valve incorrectly adjusted Mar 19, 2024 · I have a 1074 Ford 302 in a 1964 Ranchero. Ive got pink cam at the primaries and orange at secondaries. Rather, it’s the internal components attached to it that get obstructed or wear down over time. 5 pv 82 mains and 91 rears(no pv). The carb has removable air bleeds, but I haven't experimented with air bleeds before. An engine, a three speed transmission with a 1:1 final gear, and mostly deep rear gear ratios in the 4. 050 duration 112* lobe separtion cam 4* deg advance of the cam w/ relation to crank m21 4 spd long tube headers 3. I Imagine a SBC requirement would be close to that. 043”-. It seemed to surge then after adjusting the idle circuit again. I have a 1971 Chevelle SS clone. Feb 5, 2007 · Fuel Injection, Carburetion & Fuel System - Holley Street Avenger Carb Stumble - I put a Holley 670 cfm Street Avenger arb on the 390 in my 67 F100. May 22, 2006 · I had a similar problem with a holley 4160 600cfm, off idle stumble, and a stumble when cruising and then mashing the throttle it would stumble for a second or two then catch up and run fine. May 17, 2017 Jul 16, 2017 · Which intake manifold should you choose? Holley and other manufacturers offer a wide array of single- and multiple-carb manifolds. So far, the only obvious thing is a v. & no bloody bog! Test run 1000 rpm in top gear hit wot it accelerates up against the converter. Using four measurement vacuum the carbs would total 950 CFM, not 1350 CFM. … Jeff Smith: J. Holley recommends 0. Apr 30, 2016 · Continuing my issues. Nov 19, 2011 · It also runs a little rough when idling while the engine is warm. Feb 16, 2017 · If they open too late, you lose power. This particular fix (o Jul 2, 2004 · Holley's site says 2" less than idle, so I'm kinda tossed up. Before yesterday, the car ran great, better than it has ever run before. You will have to get a few larger sizes than you currently have and test them until the stumble goes away. My experience with off-idle stumble was a continuous stumble that occurred with the throttle barely open. 11, 3. 5 +/-. 4 AFR at WOT. Don't be persuaded by bad tuning; carburetor-powered vehicles can benefit from EFI-like drivability as well. Oct 28, 2007 · Holley 4150 double Pumper - kind of a cobbled together carb. They didn't see anything but suspected a bad ECU, so I sent in the whole thing in and they rebuilt it for free (kudos Holley). I have about 14 AFR at idle, and 12. 5 %µµµµ 1 0 obj >>> endobj 2 0 obj > endobj 3 0 obj >/ExtGState >/XObject >/ProcSet[/PDF/Text/ImageB/ImageC/ImageI] >>/Annots[ 16 0 R] /MediaBox[ 0 0 612 Nov 14, 2010 · Also I am lucky to have a neighbor that knows a lot about engines. It was acting like it's running out of fuel. The hesitation fix on my Holley carburetorFloat bowl gasket and accelerator pump replacementI have narrowed down the root cause of my hesitation to not getti Sep 5, 2022 · Hey guys, long time stalker, first time caller. He can now enjoy his vehicle. Sep 1, 2004 · Several attempts result in the same disappointing off-idle stumble and/or an overly rich idle mixture. 60 valves 9-9. That job is the function of the power valve and the PVRC. pump arm to take the Mar 16, 2004 · I've got a buddy that loaned me a couple carbs to try. Timing seems good. T5 5 speed. I changed The “Bog” simply means the engine is not receiving enough fuel when you go to wide open throttle. 08 gears 28" rear tires Nov 19, 2005 · Had the same proble with my Holley and read a bunch of tech articles off the web and I fixed the stumble. Jul 17, 2008 · WOT: 13. Jet extensions and notched float in the rears. May 3, 2012 · It has a stumble right off ideal that you can see and hear while under the hood. The least amount are with the Annular Discharge models. Jun 12, 2006 · A wide band 02 will learn a person a lot, it did me. Jan 10, 2011 · Though stoich is ideal for many circuits of operation, it is typically too lean at wide open throttle for the vast majority of engines and will be most happy between 12:1-13. (transitiion) This often can be tweeked just by slight adjustment of the primary idle air bleeds. It will direct you on what to do with the idle, cruise and wot circuits (low speed bleeds, high speed bleeds, idle fuel restrictions, main jetting, possible e-bleeds) There are some carb experts on hear that help out. Here is the issue: Slam on the gas from a dead stop or slow speed, the car stalls. 010" to. 4)Disable secondary and drive WOT for response to determine squirter size. It did seem that it was a lean condition and because the car is a big, heavy car it needed what seemed like more fuel and the accel pump was working properly. Pull the carb bowls and I'll bet you find debris in there and in the needle valve. Mar 22, 2010 · For example the Corvette tri-power is a 350 and two 500 CFM carbs. Jan 10, 2009 · It doesn't matter what carb you're using. 64 SS Street car. housing about . Apr 30, 2010 · Not knowing what carb # you have I can't tell you what size to change to, but it needs to be bigger than what you have. Even though it idles at around 13. Jul 25, 2020 · I also found that if I work the throttle linkage at the carb and snap it to wot it doesn’t seem to have any stumble or hesitation. If you get to this point, the carburetor probably needs to be removed, and rebuilt. May 18, 2019 · I have had hesitations with all brands of carbs from time to time. The more you know about how the power enrichment circuit works, the better tuner you will become. 10. Jul 11, 2017 · The carbs idle circuit may need a slight tweek to get the air fuel ratio right at idle and just off idle. What I mean is this, I hit the throttle full open the squirters squirt the engine stumbles like almost a backfire, then fuel flows from boosters and the engine revs nice clean Dec 31, 2018 · I put a new Holley carb 80457sa, 4160 600 cfm on my new truck motor. Many Holley performance carburetors are equipped with what is called four-hole or four-port idle mixture control. my car even sounds different than with the holley 850 dp it replaced. 5)Drive WOT and change cams for best throttle response 6)Enable secondary and make WOTs for secondary jetting inspect Jul 14, 2022 · Gotta be careful with descriptions here. 8 The primary jets are 71, secondary jets 85 So I'd like to lean out the cruise and richen the wot. Truck is standard. When driving on the freeway, it will go full lean and stall. Single-plane manifolds tend to favor upper-end power at higher engine speeds. Jul 29, 2008 · reason being the idle transfer slot is very long, and intermediate comes in and makes it even rich- so idle/part throttle is pig rich. Learn Table is down to just dialing it in. Jul 8, 2016 · But carb for carb, none of those designs to my knowledge will out-flow a Holley carb, and therefore cannot supply the demands of over 1,000 HP with a single carburetor nor even 700 HP. Although rarely necessary, the bigger pump can be installed on a 4150-style carb by using Holley’s conversion kit (PN 20-11). Idle screws are 1 1/2 turn out and if turn in 1 turn will kill the car. Mar 29, 2006 · Ok, here is the story. Page 1 of 3 1 2 3 Next > Jun 4, 2021 · The last time we talked about carburetors, we focused on getting the idle mixture and speed in line. Pump cams are orange in the #1 position. Adjust throttle linkage to obtain wide open throttle in carburetor. My new Holley 670 Street Avenger Vacuum Secondary Electric Choke was originally running very rich with a heavy bog off idle or WOT, very sluggish and a lot of popping through the exhaust. Nov 1, 2010 · Can you tell us what size the accelerator pump nozzles are? The size is stamped into the nozzle housing. Any suggestions on which way to go as far as sizing? Dec 15, 2011 · Carb is a 770 Holley Avenger (vacuum secondaries) ; max vacuum of about 14 at idle with each mixture screw turn out 1. ( ain't gonna pull 4th or 5th to WOT on the street - lol ) Just after WOT, I went to 3000rpm cruise and killed the motor, then coasted to a stop to check the spark plug. Now during hard pulls it goes full lean and stalls. On Dominator-style carbs, the pump capacity is 50 cc for ten strokes. Aug 27, 2005 · Engine and Drivetrain Tech. I runs great at idle, no stumble, quick throtle response. V8 Discussion Mar 25, 2005 · I installed a holley street dom intake p/n 300-38 and mounted a used but professionally rebuilt holley carb 600 cfm p/n 0-80457-2. car has 6. Replace with a new filter element. Dec 20, 2022 · Essentially, the problems arising with Holley vacuum secondaries aren’t so much of an issue with the carburetor itself. Jun 3, 2021 · Fuel system: Holley tank with 400 LPH pump, Holley 12-879 regulator with 3/8" feet & return line. - Found and repaired an exhaust leak upstream of the O2 sensor at the manifold donut. If they open too early you get a stumble. 7:1 - 496. All the circuits run together, so a leaner idle or cruise will also have an effect. Discussion in 'The Hokey Ass Message Board' started by Mr. 5 PW Jun 13, 2017 · Haven't been able to really go out and do much testing, but it does have huge "stumble" when going from idle to WOT. It just comes out while useing carb cleaner and compressed air. I put my old carb (600 holley, vac secondaries) back on and it now runs Dec 3, 2018 · Related: 10 Biggest Carburetor Tuning Mistakes We also interviewed Holley carburetor tuner/restorer Sean Murphy of Sean Murphy Induction (SMI) to document a few of his tuning and assembly secrets. Current jetting is what Holley gives as a baseline for the HP main body upgrade, which is 72/84. Avoid non-Holley brand kits, as they might not include everything, and may not have the same quality of components. Carb has 30cc pumps, stock cam, and . I actually think its running rich and not lean. motor is a 355 ci flat top pistons, around 9:1 CR was wondering if going to 69 jets would help. They will need orifice diameters and can give a good baseline to work with. Set everything to spec according to Grumpy's thread 831 on carb tuning. I have no stumble and great throttle response when opening the throttle quickly and leaving the line. The engine will start getting real choppy from the lean condition while easing into the throttle. When I crack the throttle, I get a studder but then it clears. This is a renewal kit (PN 37-485) applicable to 4150 carbs in 600, 650, 700, 750, 800, and 850 cfm. as soon as you touch the throttle there is a dead spot or pause and then accelerates and runs great. 031 nozzles. I've seen these issues on the Tuning for Beer Tours, and I just had yet another SA carb (the 4th one with these issues) sent to me with Mar 23, 2010 · The car has a very mild 351C 2V with and Edlebrock Performer, and a 700 Holley double pumper carb. Sep 4, 2010 · Make sure the pump arm is adjusted properly. Best way to figure it out is disconnect the secondaries and work on one side of the carb at a time. Yours may be a just a hair too big creating a off idle transition lean stumble. Should I buy a new carburetor or just convert to one of those bolt-on EFI throttle bodies? — J. Dec 2, 2009 · Holley explains how the main jets on a four-barrel carburetor operate. This carb has vacuum secondaries, so that may be why the secondary slot is so high. This will ensure you get enough fuel for a WOT slam until the primary circuit kicks in. PS - the QFT 50cc pump lever arm is different than the regular Holley 50cc arm. , etc. I know this is a common problem for holley's and I've done some research on a solution and have not been successful. Make sure of course you plug the vacuum line so it is sealed tight. Changing the bowls will affect the adjustment. Power system not operating. At part throttle- response is great. I'm new to this thread. Feb 27, 2022 · My Holley carburetor has a stumble and or bog going from idle to WOT. Still going to dial the timing in more as well, but for now it's running mint aside from this tip-in stumble and Jun 3, 2022 · My guess is that the needle valve on the secondary float is contaminated or stuck and you are dealing with fuel starvation on hard acceleration. What will happen is if I'm sitting there idling (in neutral) and go to wot quickly, it'll bog so bad it seems to stop running for a second, then picks up and revs again. (Check by pushing accelerator pedal to floor). Holley has really good adjustment instructions on their website which helped narrow down my problem. The purpose for this clearance is to Jun 3, 2022 · 4000 acceleration issues holley stall stumble teepot wot Replies: 36; Forum: 1955 I recently rebuild the Holley carburetor (600 CFM 4160, hot air choke, vacuum Jul 25, 2009 · I cant seem to get the stumble out of my 4779 750 DP. 5 is correct. WOT- carb falls on face for a moment then gets it. 9-13. Nov 11, 2023 · Through my cowl hood vent, I have seen flames shoot out of the carburetor on occasion while going WOT both off a dead stop and at highway speeds. I just checked WOT and it's basically 0 to 1" to the limiter in 2nd and 3rd. White and blue (most aggressive) are good candidates. 02 angle plug heads, Comp cam 4. 02/1. But without useing the spray carb cleaner to check for blockage. Correct any sticking or binding conditions before proceeding. Problem is a severe stutter when snapping throttle open off idle, Sometimes will backfire through carb, Nov 23, 2022 · The most common issues with Holley carbs are flooding and incorrect fuel/air mixture. May 14, 2013 · The proper adjustment of the pump arm is critical. I need help with my carb. made a huge difference, almost no hesitation. I've managed to get the carb to idle at about 12. Dec 12, 2008 · Try unhooking the vacuum advance and see how it operates. I finally got the Edel 600 running quite nicely, so I wanted to compare it to his Holley 670 Street Avenger. runs out smooth once it is good and warm but when cold it is pig rich. I have a AEM Wideband on the car and at idle it is reading about 13. 6 aluminum roller rockers, Mallory electronic ignition. My 318 has the choke thermostat that operates as it should, and it runs great before the butterfly is fully open. May 31, 2008 · Fixing a stumble- Holley DP carb. 5-14. I did find a bad spark plug, but it did not help the stumble. Aug 18, 2016 · 30cc pump, 31 squirter, orange cam - stumble, then go when I stab the throttle 30cc pump, 35 squirter, orange cam - Jerk, then stumble, then go when I stab the throttle 30cc pump, 35 squirter, blue cam - Jerk, then stumble (about as bad as with the orange cam, maybe a little better), then go when I stab the throttle Nov 29, 2015 · Popping back through the carb (as opposed to an ignition back fire) is the result of running lean (more air than fuel). This is a common problem with double pumper carbs that can force all four barrels open by stomping on the gas. It idles about 900-1000 in neutral and about 700 in gear. Without touching the carb the idle is better has picked up around 150-200rpm is smoother & lambda reading is around the same at . Feb 21, 2024 · . 75 lift 3. Oct 7, 2013 · holley alum heads 2. The sales pitch - if the carb needs rebuilding, we can probably help you with a rebuilding kit. An externally adjustable needle and seat assembly is used so that the float level can be easily adjusted without the need to disassemble the carburetor. Jul 16, 2017 · The kits include everything needed to make your Holley carb fresh following a disassembly. I have found the key to carb tuning is to change 1 thing at a time and on things like the pump arm adjustment. Jul 19, 2011 · Just installed my fresh 383 with 750DP carb and just trying to find-out what tuning issues there are and how to resolve them. Jan 11, 2016 · Look for about #58 - #60 primary jets in Holley 600 carb floats set at proper levels no slop in accelerator pump linkage slightest movement of throttle lever off idle should also move the pump arm make sure timing is advancing as engine is revved use direct to intake manifold vacuum to distributor vacuum advance a compression test of all 8 cylinders will let you know if you Jul 16, 2017 · Continue this line to the carburetor size range at the far left. Having your idle in line doesn’t mean Apr 23, 2012 · I have the same exact problem with my QFT 750 cfm carb on a carbureted 350 LT1. 4-13. This is a carb, not fuel injection. I rebuilt this carb twice, and tried several different setups with jets, pump shooters, pump cams, etc. %PDF-1. Here are the carb changes I have made: Primary jets were 65 changed to 68. 10 duration, 1. Aug 2, 2017 · Carburetor throttle valve (s) not going wide open. You Jul 14, 2010 · The amount of air bleeds a carburetor will have is dependent on the number of throttle bores and circuits the carburetor has. Vacuum now is a solid 14 so a 6. 1comp, XE268H cam,vortec heads, perf. The fuel pressure is only one part of the equation in supplying the fuel to the carb, which only fills the fuel bowls, none of this has anything to do with how the fuel gets from the bowls into the airstream flowing thru the carb throats. The engine is a Chevy 350 with a Holley that is not the original engine or carb in my Chevy. Jul 27, 2015 · Strange as it may seem, the main jet on a Holley carb is not what you should be using to calibrate the WOT mixture delivered to the engine. Holley HP carb, full MSD ignition (mech advance dizzy). At high RPM with a 500 (or 350) CFM two barrel on a 350 engine the vacuum is high enough to pull extra fuel through the carb and cause the engine to go rich at RPM. Previously would just stumble Nov 17, 2006 · 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. Symptoms, when the car is under load and at low RPM ( 1500-2500, slow cruise or highway cruise) the car stumbles or misses. these carbs can be lean at WOT even with the jets removed. Most QFT™ carbs come from the factory with . May 17, 2017 · I am assuming the air fuel at wide open throttle is in a good range 12. Sinister, May 6, 2011. There should be no play in the linkage at idle and at wot there should still be another . The vehicle is a 70 El Camino SS 396 with a Q-jet carb. 3 to 11. PISTON TYPE – Check power piston for free up and down movement. 037 made a big difference for both part throttle snap and WOT snap, both now more of a stumble. 048” power valve channel restrictions. Sometimes backfires through the carb after a quick throttle blip. I filled up the tank and still did the same thing. Apr 13, 2014 · I had an off idle stumble at throttle tip in on my car and solved the issue with a smaller squirter. Most racing carburetors will have either 8 or 12 air bleeds depending on whether they are 2 or 3 circuit. It has a Holley HP main body, 650 DP metering blocks (4777-2) fuel bowls and throttle body. 350 chevy engine, 350 turbo automatic, 4:56 rear end. Carb was running on idle jets and transition slots. choke 65 pri and 68 sec using 'middle' spring lunati . To get the idle Dec 4, 2020 · Holley’s recommendation for setting the pump linkage refers to ensuring that the linkage does not bottom out, creating a bind that could bend the linkage. Mar 30, 2009 · Hey guys. Dirty or plugged fuel filter(s). All carbs are good, and all are tuneable. Nov 21, 2005 · Turbodave's link should be read by everyone running a carb. 5 turns. So here's our issues: - Lean condition during light acceleration. May 4, 2020 · ALL OUT Tech- Simple Fix for Holley Carburetor StumbleToday Dan owner of DaVinci Performance Carburetor shows a neat little trick on how to take the stumble Jan 19, 2012 · Trying to figure out my lean stumble when flooring it quickly. , we can definitely help you. Hesitation is when you step on the gas and the engine falls flat on it’s face. Center Pivot/Hung Float. P. Jul 15, 2015 · Bad Gas Milege, Off Idle Hesitation/Stumble Blazer72 wrote: Well increased the initial to 18, went ported on vacuum advance, adjusted throttle plates, lowered total rpm to 2000 rpm. Disconnect secondaries and bog is gone. The main jet, however, is the most often changed jet; the one changed in an effort to optimize the mixture for maximum power. They also give instructions on changing the jets for increased performance. They are number stamped into them, sized in steps of three usually, ie 25, 28, 31, 35, 37, 40. I guess the cooler weather was missing with the carb. Those carbs are generally reserved for all-out drag cars that run WOT throughout the run. Nov 7, 2006 · The Holley 600vs carb is notorious for a fairly lean idle mixture. Aug 22, 2011 · Make sure both carbs open fully when the gas pedal is pushed to engage wide-open throttle. Stick with the 31 squiter, When you take the carb off show us where your throttle blades are. Or even more simple, Most carbs have a screen on the fuel inlet into the carb and it could be clogged restricting flow. . WOT target AFR is 12. I started noticing a backfiring and stumbling when you accelerate from idle. did a vacuum test Dec 19, 2020 · The mechanical secondary Holley is know as a progressive linkage style and it’s pretty rude and simple how it’s engineered and works sweet and simple that rod between the primary n secondary butterflies makes a ratio between the two there are specific carbs designed to have a 1:1 ratio out there I’d hafta surf web to see if for most May 6, 2011 · Light throttle stumble, Holley carb. Primary has 30cc pump, 35 squirter, and pink pump cam in #1 position, no slack in linkage, can't remember secondary squirter size, but has 50cc pump, brown cam in #1 position. I'm not putting a load on it to warrent the PV opening. I would advise going to the pink #330 cam as that will give you the most pump shot for a 30cc pump. 015 at WOT. In this case, a 650- to 700-cfm carb should be adequate. WB confirms PT snap doesn't go lean, WOT does. Sep 6, 2009 · In most cases a bog at WOT is caused by fuel starvation not flooding. 477-. Edelbrock Streetmaster intake, mild street cam. 5. The carb runs well, linkage adjusted correctly, jetting is fine. 5:1 ratio at part-throttle Nov 19, 2019 · Another vital point is that the tuner should always shoot for the smallest nozzle the engine will accept. Dec 4, 2007 · Fuel pressure has nothing whatsoever to do with it. My Stang came with the same Holley carb. Fuel Inlet System. It also had a stumble when accelerating when the car was already at speed. I figure the simple way to tune this carb would be to jet a bit smaller on the primaries and a bit bigger on the secondaries. and elec. But I cant go over 12. The previous owner had a friend build him the engine when he totally rebuilt the old girl from the frame up. Used the million posts of great advice and info on this forum to get my Sniper as far as it is, chasing away the gremlins. Fires up and idles great. The 'Holley stumble' is usually created by not enough fuel being delivered at WOT. In this example, if the minimum RPM at which you expect to use WOT is about 1,350, and the engine size is 350 ci, the maximum suggested carburetor size is just a tick below 700 cfm. The air fuel ratio is good and really doesn't fluctuate. Jul 21, 2009 · I don't understand. This helped but I still had a stumble at cruise around 2,000-2,500 rpm in 4th gear. Since then, I've tapped and threaded every orifice in the metering blocks, as well as the TSR's in the main body. This makes me think that my carburetor is running lean and needs a little enrichment for it to not stumble when the engine is warm. At wide-open-throttle (WOT), a smaller nozzle size lengthens the duration of the pump shot compared to a larger nozzle. I know I have 25 nozzles in the primary and 32 in the secondary. Would changing the color spring out help? Holley tech paper says it is set up with the spring that gives best all around performance and economy. 015 of movement available to avoid bending parts. Jul 5, 2012 · 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. 031 part throttle snap sounds like I hit the throttle twice 1/2 a second apart, WOT snap stalls like the key was shut off WB shows instant lean. May 17, 2021 · Few double-pumper carburetors open the secondaries at a one-to-one or on an equal percentage rate as the primaries. I bought a jet kit for this because there is a stumble when I stomp on it. idle is good, performance is awesome, air fuel mixtures seem right on the money. and i am having problems with a flat spot as soon as you accelerate at any speed. Vehicle: 69 Chevy C10, sm465 manual, 383 stroker, Dart Pro comp 215cc heads, edelbrock 7501 air gap intake, Holley 670 SA, comp cams XE284h-10 12-250-3, 450hp, 450 lb/ft. Your supposed to bench set them @ WOT with a . Oct 20, 2001 · I put a 4150 600cfm Holley on my Dad's truck, it was great for a year. Aug 2, 2008 · The stumble sounds like a lean out condition and when looking down the carb while accellerating the stumble seems to occur just before the boosters start suppling fuel. The engine was just rebuilt, and the carb was also restored and rebuilt. 5:1 - 13. Aug 15, 2013 · I have a 410 small block Mopar and I bought one of the holley 850 carbs and I am having a bit of trouble getting rid of a off idle stumble and over all tune is crap. Nozzle size controls more than just the initial volume of fuel — it also determines the duration of the shot. 31 size pump nozzles. 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. Set the transfer slot to . slight stumble when suddenly going from part throttle to WOT. The engine is a 350 with Vortec heads, Comp 268H cam, air-gap intake, and new Holley 4160 600cfm (list # 0-80457s). Aug 24, 2007 · First, here's my setup, Ford 331 stroker with a Paxton blow thru (enclosure). Operate the carburetor throttle lever by hand to assure the correct travel (no sticking or binding) by opening to wide open throttle and back to closed throttle several times. I'm new to carbs so keep that in mind. 50 range. Had the worst luck with a 600 Eddy carb, found it was the secondary side, got it fixed and it was lighting quick after that. Incorrect adjustment is the typical culprit. Apr 11, 2019 · I have used the holley HP carbs and the quick fuel brawler carb and the classic holley double pumper which I converted to a 4 corner idle system several years back and I have used them on three different builds and I also have done a lot of research on setting and tuning holley four corner idle carbs and the old Demon brand carbs from early Jul 27, 2015 · Replaceable idle air bleeds (yellow arrows) are used in the top-of-the-line street and race Holley carbs, making a change easy. - While cruising at low speed (<40 MPH), engine surges lean, then rich, then lean, then rich, etc. it works good but think the jetting my be too rich or something. idle still a little rough, and a little loss of mid to top end acceleration, great bottom end, but getting closer. The car came with the 400 with the Holley 750, Edelbrock aluminum heads, beefy looking rockers, a good sounding cam, and long tube headers. And obviously with digital you would be able to make a better decision as to how much of a change to make. In the context of racing carburetors, it helps to think of them as (4) one barrels. 5:1. Holley pro series carb, turbo B&M 400 Jul 28, 2015 · The stock accelerator pump on a 4150-style carb has a capacity of 30 cc for ten strokes of the pump. then at WOT, the idle feed restriction tubes in the main jet wells, restricts WOT flow, and leans WOT out. Helps in understanding what each does Feb 2, 2020 · How to fix Holley accelerator pump stumble caused by a sudden lack of fuel (or too much fuel) when aggressively opening your throttle. Dec 2, 2009 · Footage taken from Holley Carburetor Installation & Tuning DVD Get expert technical support for Holley Performance products, including EFI systems and fuel injection, on the official support page. 73, & 3. 015". This has worked for me on a part throttle to wide open throttle stumble. Perhaps a mech secondary carb with 4 corner idle has lower slots, but I really don't know. Jan 31, 2021 · If you logged such an issue you would simply correct via carb tuning. Dec 17, 2020 · Wide-open throttle: 11. entering the carburetor. 5:1 compression Holley 670 cfm street avenger carb w/ Vac Sec. This assembly delivers an initial shot of fuel in the right amount, and duration, to provide crisp throttle response right off idle. I've played with timing, idle mixture screws, checked for vacuum leaks, fuel pressure varies from 5-6 psi, changed pump arm positions, adjusted idle speed screweverything but bought a needle and Jan 9, 2015 · I am trying to cure a carburetor hesitation on my newest member of the family. These tips apply to all Holley carbs from 4150 to 4160 to 4500 series. But when I'm driving and get on it, it will stumble for a split second and take off. On some carbs changing the spring/weight is easy and aids tuning, but on others like the Holley it’s tricky to do on the engine and the choke has to be removed. You can hit the throttle hard enough to pump fuel into the engine and launch with tires Sep 17, 2015 · About a month back I swapped in a brand new Holley 1850 carb on my '66 (motor is a Fast Burn crate 350 with Edelbrock performer RPM air gap manifold). Tried the rear plates open more, and less on the fronts. Oct 9, 2002 · I read the following quotation off the holley web site reguarding the accellerator pump adjustment. I used a pink cam in #2 position with large nozzles and this fixed my WOT issues. Having the right transition mixture is the reason that some people think that a Holley is better than an Eddy, is better than a Q-jet. Dec 22, 2015 · So, if your vehicle is surging or coughing through the carb (popping) at wide-open throttle, you can richen it up with larger restrictors. 5 a/f, it seems crazy rich just from the smell and the eyes burning. Jul 16, 2007 · C3 Tech/Performance - Street Avenger Stumble Issue Solutions - I keep running into Holley Street Avenger carb problems related to off-idle stumbles and part throttle hesitations. Rated in inches of mercury (InHg), as an example, the most common rating is a 6. I'm guessing it's not getting any fuel so the squirters aren't able to keep up. The first thing to do is to look at the discharge nozzle and make sure you are getting a good strong pump shot. May 17, 2017 · These will be the correct heat range or very close. A very broad generalization is to select a […] Jul 26, 2020 · Do you have any tips about tuning a holley 850 double pumper at cruising. After installing the Sniper 2, it ran good for about two months. No sure way to tell were it's lodeged PS useing spray carb cleaner is a great visual medthod to find and identify all the metring cucuits in a carb. dont know if it is the secondary power valve or what but the carb acts a bit strange to me too at wot. You Can Also Read: Holley Carburetor Troubleshooting: Tips and Tricks; Holley Power Valve Identification: A Simple Explanation Nov 27, 2005 · '64 Chevelle 383ci 10. The carb is a Holley 750 cfm double pumper (4779 if I remember correctly). I suggest try bigger nozzles and if needed place a 50cc pump on the primary side with a sharp nosed cam. rpm airgap intake, Holley strt avg 670cfm vac sec carb, MSD HEI dist w/6AL box The engine stumbles when at WOT, wether it's off a rolling start, or cruising at 40mph and punching it, but ONLY at WOT. and jetting down to try to clean up the idle Apr 29, 2009 · i have a brand new holley 600 cfm vacuum secondary and electric choke carb on a new 350 engine with a 700r4 trans. As the throttle opens, manifold vacuum drops from a high of around 16-18 InHg down to around 0. I have been trying to dial away an off-idle hesitation and have tried swapping springs for the vacuum secondaries, different size pump nozzles, different pump cams, etc. I fooled with it for another 3 years until I replaced with an Edelbrock #1405. If this helps you may have a smog friendly VA on the carwhen you stomp on the gas pedal and the carb blades open there is a decrease in pressure in the plenum and the vacuum drops considerably, takes a while for the airflow to get moving through the intake to create Dec 28, 2014 · If it bottoms out @ WOT it will damage the accel pump. Jul 4, 2024 · I've spent the last 3 weeks scouring forums for answers and have learned quite a bit about tuning the circuits of a Holley carb. 85 at idle. Fuel line is intact, vacuum line from stock points distributor to carb and carb to pcv hooked up all other vac line on carb are plugged and electric choke is working. Even Holley says to run a PV half of what you read at Idle. So I changed out the quirters from 31/28 to 35 in front and 31 in rear. 7 and WOT is now 12. Zach says that . Nov 15, 2023 · In this video, we explain the most common fixes for a off idle stumble on your Holley Carburetor. On the road it is worse. There should be no play between the arm and cam at idle and you need to be sure that at wot there is still some extra room for movement (. For a progressive linkage, adjust the linkage so that the rear carb opens slightly before the front Jan 25, 2019 · The car runs fine once the rpm is up and cruising, but it has a terrible stumble when I hit the throttle. - Replaced all plugs, Ohm tested all plug wires Jul 4, 2019 · Holley’s power valve is a simple, spring-loaded diaphragm valve that uses engine vacuum to pull the valve closed. The most common cause of a stumble is not having an adequate accelerator pump shot. 6 for my Charger and it goes there and stays there as soon as WOT. Had to richen up the idle mixture screws by one turn and raised the fuel level to the proper height. Jun 22, 2023 · I have a situation re: carb stumble and backfire under acceleration. I think adjusable air bleeds may help, but my carb doesnt have the screw in air bleeds Carb is now 74 pri, 86 sec, 4. May 13, 2014 · 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. 3)Drive and check plugs for primary jetting. I ran my truck with my old edelbrock for a couple weeks before i bought this Holley. 015" feeler gauge so they don't bottom out. inspect white insulator. The car would stumble as soon as the throttle was cracked open from idle. 0, and at cruise(3000 rpm)it is reading about 11. The carburetor is a Holley 750 with vacuum secondary. So far I have put in a 3. The adjustment procedure is exactly the same except that all four idle mixture screws are adjusted instead of just two. But that’s not all that a carb requires of its owner. Seems like its too rich in the secondaries. The stumble isn't from the PV. And when I say "stumble", I mean it stumble, then die. I bought an 88 Chevy truck, the truck has a STOCK 350 motor, Edelbrock intake, and aftermarket air filter with OF COURSE a Holley Street avenger 770 CFM Carb (08770-1) which is a 4150 if I have done my research correct. Sep 29, 2011 · Ok, so to describe the stumble. Jan 20, 2014 · Reconnect the throttle and transmission kickdown linkage and throttle return spring (Holley P/N 20-89). 507 lift 225-235*@. I was told to replace the discharge nozzles to correct this problem. Nov 11, 2011 · have one on my 10. eegx zhziuqh kebo myk teehc jhmlxl pifmxmh nkgjc zymu rsus