Holley Carb Part Throttle Stumble

My advice: Buy an Edelbrock #1409 and mount it with a 12-degree carburetor leveling wedge. If you don't see what you're looking for here, please contact our friendly sales staff either by phone or email for assistance!. There's nothing like the look and feel from a Holley double-pumper carburetor. This carburetor is SO smooth it makes me wonder why I didn’t switch years ago. Keep in mind that, due to differences in air and fuel delivery to individual cylinders, we’re speaking of average, not absolute, air/fuel ratios when dealing with carburetors. For this article, we’ll be using a Holley 4150 Series 750 double pumper, pictured here. The second place depends on "both" the secondary throttle blades, and the "adjustable" air valve to be open You should all ways be pulling high vacuum with a Edelbrock carburetor on a Dual Port intake. Usually the model 4150 carb has a mechanical secondary, but the List 4609 has vacuum operated secondaries. Please have the part number of the carburetor you purchased on hand when you call. If the adjustment is to be made off the engine, open the throttle valve and move the choke to its closed position. The motor is a FRPP 302 crate with supposedly a "mild" cam and edelbrock rpm air gap intake, hooked to an AOD trans. Do you have a good fuel filter and a good 4 to 6" tall x 14" diameter air cleaner? Tiny low-profile air cleaners kill power and throttle response. Not yet installed. On a fuel-injected car, a throttle body that is too big will put too much gas in the combustion chamber that just flows the exhaust unburnt. GM 3 bar MAP Sensor part# 12223861. As the name implies, the accelerator pump provides additional fuel upon acceleration of the engine, while the primary circuit catches up to demand. Choose top quality brands Edelbrock, Holley, Uremco. And unlike the Edelbrocks, you can get a new bowl vent equipped Holley 4 bbl too, to help with hot restarts and hot weather driving. The surging at idle might be the carb, but it could also be your advance mechanism in the distributor too. Of course a big 4 barrel will run, at the expense of throttle response and fuel consumption. It has a Performer intake, CH-4B old school. This will produce an instant pump shot off idle, and will solve most of the hesitation/stumble issues associated with these carbs. & I at first went back toward the blue and white cam,. I had a similar symptom of part throttle stumble that I just finely, after screwing around for 2 years with it, got it solved. 56 gears out back. Holley carburetors have four distinct circuits of operation: idle, off-idle, cruise, and wide open throttle. In Part 2, Demon Carburetion helps us identify a few more chief components of the modular, square-bore carburetor, acquaint you with common problems that can arise, and tell you how to prevent them. Initially I had some idle issues where it would occasionally die at idle but that problem has resolved itself as the system learned how to compensate. 1968 Mopar 440 950 CFM 3 Barrel Holley Carburetor List 3916-1S Dated 834. 6 exhaust valve,torker intake,headers and a mild cam, 727 with 3000 stall and 3. If you haven't done this then afterwards re-adjust your carb's A/F mixture screws. Commonly done by checking lead or front barrel of each carburetor. CONGRATULATIONS on your Summit Racing Street & Strip Carburetor purchase! Should you need information or parts assistance, please contact our Technical Service Department at 1-330-630-0240, Monday through Friday, 9 am to 9 pm Eastern Time. RPM intake, Doug's Headers 3" Pypes exhaust. I had the softest springs in the mech advance, thinking get the timing in fast. Holley Performance Street Carburetor - 500cfm 2 barrel Holley's famous Street/Strip carburetors feature power valve blowout protection, and center hung float bowls. Anyway, thanks for replying. I posted a second question on the edelbrock forum "design change: spreadbore and squarebore plenums". I have adjusted my engine's idle speed rpm by slightly opening the carb's secondary throttle blades. The car would stumble as soon as the throttle was cracked open from idle. So on my jet boat I went with the 850 Mighty Demon, tuned it once and never touched it again. How to tell what size carb you need: You take the engine cubic inch and multiply by the maximum RPM and divide by 3456. These carbs have the less desirable needle and seat assembly and float fulcrum location, so unless the carb is being used on a restored or period correct build, the later carbs- especially those with the adjustable part throttle adjustment or 'APT' located on the airhorn- will be a better choice for a performance application. As Holleys are typically performance orientated I would start with a 8. My car is a 67 Corvette, stock 327/300hp engine with it's stock 3810 Holley (585 CFM), this carburetor is generic to the 300 & 350hp engine and they have two completely different sets of valve timing. Ive never personally ran an edelbrock since taking the one off my first foxbody and throwing it in the trash. The demon was not a marine carb, however I have been told you can buy the "J" tube and install it. CONGRATULATIONS on your Summit Racing Street & Strip Carburetor purchase! Should you need information or parts assistance, please contact our Technical Service Department at 1-330-630-0240, Monday through Friday, 9 am to 9 pm Eastern Time. Holley Carb Baselining/Tuning It's been a while since I've been asked a carburetor-related question, but this one came up this week so I figured I'd do a little writeup. Would not leave clean until staged on the brake @ 3100. 56 gears out back. These products are shortlisted based on the overall star rating and the number of customer reviews received by each product in the store, and are refreshed regularly. Holley type carbs come with a standard shooter size which differs by carb list #. On a Holley carburetor, this is usually the nipple located on passenger side of the primary metering block. A better description of the symptom would help us to ascertain whether the accelerator pump circuit or transfer slot is the problem. I have a 65 Chevy C20 with a 327 from a 66-67 Impala, that originally had a Holley 4160. It will feel like someone is moving the throttle when they are not or a hesitation on light throttle acceleration. It seemed to only happen once, and working with carbs as long as I have, I have seen many new and rebuild carbs leak a few times until the new needle and seat get broken in. The car has a very mild 351C 2V with and Edlebrock Performer, and a 700 Holley double pumper carb. That was the end of the subject. At part throttle, a carburetor delivers its best fuel economy at 15:1 and numerically higher lean air/fuel ratios. HGM’s AccuLink is a really slick chrome steel conversion package that provides a GM-style TPS sensor to all in style Holley, Q-Jet, and Edelbrock carbs. Unlike a Holley, which uses a power valve, the Quadrajet has primary metering rods and a power piston, which is sometimes referred to as an adjustable part throttle (APT). It also had a stumble when accelerating when the car was already at speed. At higher RPM's it runs great until the stumble occurs, always at part throttle. They both have the same bolt pattern as the WW, but there may be choke and throttle linkage issues to iron out. I am having a hell of a time getting my carb to get both a clean idle and no part throttle laziness and cruise lean condition. You can get them at any auto parts store though if you know the part #'s since its the same ones holley still uses. Once the engine spins up a bit, it does ok. Carburetor Parts > by Part Type > Idle Mixture Screws; Carburetor Parts > by Carb Types > Carter > BBS > Screws - BBS; Carburetor Parts > by Carb Types > Rochester > Monojet 1MV, 1ME > Standard and Idle Mixture Screws; Carburetor Parts > by Carb Types > Holley > 1909 > Screws. The amount of air is held constant by the throttle position so the AIR FUEL MIXTURE delivered to the engine is controlled by those screws. If the carburetor is damaged a replacement numbers matching carburetor could be quite expensive. I found a parts carb on shelf and changed power valve, this cut the puff smoke down,but still their. If you read my post, if you do this you must readjust the accelerator pump. A lean fuel mixture can cause an engine to have a surge or miss at idle and part throttle stumble on acceleration, leading to engine overheating and lack of power. Identifying the Carburetor's Circuits of Operation. At about 2500 RPM, when the throttle is opened there is a pronounced flat spot until finally the rpm's climb. Buy a 1978 Ford F150 Carburetor at discount prices. The design allows the bowls to leak way too often. Different carburetor systems use different parts to adjust or tune these areas. The brass pin is shoved in all the way so it totally blocks the hole. This is a discussion on Holley Carbs within the Drivetrain forums, part of the CJ Forums category; So i was calling around for rebuilds today for my carter and IO, i called Oreillys they are the cheapest. I believe the Holley HP 750 to have an inherent problem of leaning out severely at part throttle tip in as the vacuum decreases, but not before PVcomes in. I went from 66 to 58 mains, REVS better on top, but no change in puff smoke. 5 and timing is 36 @ 3000. Hope this helps. On most S/A carbs, the secondary throttle (idle speed) is fully closed. One issue I am havingis with a part throttle input / crusie. New Made in USA; Includes Flange Gasket (choice depending on application) Extra cork flange gasket (some prefer the cork style) Throttle body gasket; Instruction sheet - electronic; Float bowl gasket. The carb number on a Q-Jet is usually stamped into the bowl casting on the driver’s side of the carb in the area above the secondary throttle shaft. The primary side is the most used and has the idle adjustment that feeds fuel from below the throttle plate. Once its stuck grab the secondary linkage and push it closed. The carb number on a Q-Jet is usually stamped into the bowl casting on the driver’s side of the carb in the area above the secondary throttle shaft. This is not ment for the race car guys and is intended for the performance "street" car guys with this issue. It is a bit acedemic anyway, as long as the pump shot goes down the carb throat there will be plenty of turbulence as it passes the throttle blades and into the manifold to vaporize the fuel. The secondaries should have nothing to do with your problem unless something is drasticly wrong. Holley secondary stumble Got a stumble when I crack the secondaries on my 650 holley that I'm having a hell of a time tuning out. Lowering the front float helps this condition. Help With Troubled 4180 Carb I have an '84 Mustang with the orginal Holley 4180 carb. This will add timing at part throttle under light acceleration and will often cover up a part-throttle stumble. In an 18 foot flatbottom with 18% gears and a 11 1/2" by 15 prop the carbs held 10" of vacuum up to 5500 RPM. Mixture Screws: Turn clockwise until the engine starts to stumble and backout screw 3/4 turn. The problem I have with my 63 Impala is what holley calls a "tip in" stumble. Just about anything under 3k will stumble intermittantly if I leave the throttle in the same position long enough. Per your stumble, look at your accelerator pump linkage and make sure there is a tiny bit of preload on the pump arm at idle. I had the softest springs in the mech advance, thinking get the timing in fast. Different carburetor systems use different parts to adjust or tune these areas. Would not leave clean until staged on the brake @ 3100. if your trying to lightly throttle up then you might try the upping the valve. For this reason, the Stage 3 carburetor might exhibit a rich condition at idle and low speeds, due to the calibrations made to operate properly under high-RPM racing conditions. So I modified a bracket that fits on the back of carb for the throttle cable. One, there is hesitation opening the throttle from idle, once that clears it seems fine. The last two numbers are the size of the rods. I just put a 57 b intake and holley 390 cfm on my 55 with a stock 292 and A/T It had A intake with a 4v teapot before/ it sure rans alot better but I have a small stumble when I take off / so far I have check the float level,accelerator pump arm adj,move the pump cam to the #2 postion Im starting to think that maybe I need to replace the pump shooter which is a. Holley carbs come with a standard shooter size which differs by carb list#. Keep in mind that you will need to re-adjust the accel pump lash adjustment after you bend the arm. Holley Carburetor 4160 Street 600 CFM Polished Aluminum 4V With V-Bowls is rated 4. The Holley jet kit is worth the 50 bucks, two jets each size 64-99. Lots of folks lately with Holley issues. The idea is to get comfortable with your new carb, pay close attention to little things like the proper way to hook up the throttle linkage and what to adjust and what to leave alone when you first fire up your engine. There was a special engineered carb for the 427 GT-40 that had the secondary’s cammed to open with the primaries and brass bushings in the throttle shafts. The carb number on a Q-Jet is usually stamped into the bowl casting on the driver’s side of the carb in the area above the secondary throttle shaft. On a Holley carb, check float levels too. The stumble isn't so much RPM specific as it is steady part-throttle specific. ): This may be caused by inter­ ference between carburetor main body and end of therm­ ostatic choke lever rod. Holley carburetors powered every Monster Energy NASCAR® Cup team and nearly every NHRA® Pro-Stock champion for four decades. The carburetors must return instantly and positively back onto the idle set screws every time the throttle is released. 20 Summit Racing) that was followed by a Proform throttle body conversion (PN 67101C, $125. AED Performance HO series carburetors are 100% hand built & machined in house to our "wet flow" specs with the Pro Street and drag racer in mind. 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. 020" travel remains in the accelerator pump linkage. Car was running great outside of a slight stumble at cruise. 5's may be opening too early or opening during cruise mode or part throttle so a valve/valves that open later or at a. 5 for one carb power valves were dumping too much from two carbs and loading it up. Holley Carb Serv Parts (bwls, blcks), Throttle Body Kit, 0-80670, Part #112-114. The part numbers for 75' and later primary rods start with 170513xx, as in the. My gas carb (ProForm center + QFT parts) did the same thing. The last two numbers are the size of the rods. Holley Carbs. I'm still experimenting with it. I have a 65 Chevy C20 with a 327 from a 66-67 Impala, that originally had a Holley 4160. The key to the CV carb is the vacuum controlled slide. I am running a Blue pump, -8AN line, 40 micron filter before pump, holley reg set at 7 and a paper type filter. STEP 1 ~ Block off the power valve with a proper blank power valve from Holley, part# 26-36. However, on engines that require considerably more throttle opening to hold an idle the pump cam is already past it's peak fuel delivery point and on the downhill part of the curve. On a Holley it's pretty easy to change. As the name implies, the accelerator pump provides additional fuel upon acceleration of the engine, while the primary circuit catches up to demand. In the Holley 4-barrel carburetor there are these eight flow systems : Operation primary fuel inlet • primary idle • idle bypass secondary idle primary main metering • secondary main metering power enrichment accelerating pump Primary Fuel Inlet System. an off-idle stumble or a bog, you'll need to make adjustments to the accelerator pump and possibly the power valve to suit. Extreme part throttle lean out, Holley HP Greetings. Too little or no transition slot exposure on the primary side on most engines will cause a stumble or hesitation on tip-in. The owner said it had never been used and it looked new. Install fresh throttle-return springs on the carburetors. She was running great up till this point. Carburetor Parts > by Part Type > Idle Mixture Screws; Carburetor Parts > by Carb Types > Carter > BBS > Screws - BBS; Carburetor Parts > by Carb Types > Rochester > Monojet 1MV, 1ME > Standard and Idle Mixture Screws; Carburetor Parts > by Carb Types > Holley > 1909 > Screws. Part 2: Since adjusting the floats, I have a bit of a stumble while slowly or moderately throttling up. With the key off, look down the carb & steadily open the throttle. There, an oversized carb will make the engine actually perform worst at part throttle. Holley carburetors come with a standard shooter size, which varies by the carb list #. will start to stumble around 2 turns out. The primary throttle blades ( transition slot ) had to be perfectly squared and the mixture screws richer than I liked to eliminated that transition lean stumble. finally got truck going in and out of overdrive smoothly. Check with local circle track guys if you don't know anyone that can set up your carb for you. he had no other opinion about it. Edit : I changed the title back also, as I wanted a future search user to understand how - what appeared to be a carb issue could be confused for an ignition issue or coil problem. I wanted better fuel economy and was tired of the constant carb tweaking, so I installed the MSD Atomic TB EFI kit #2900. 20 Summit Racing) that was followed by a Proform throttle body conversion (PN 67101C, $125. Holley carb tuning Welcome to Rods 'n' Sods, the most active and friendly UK Rod and Custom website. The car has a very mild 351C 2V with and Edlebrock Performer, and a 700 Holley double pumper carb. You can get them at any auto parts store though if you know the part #'s since its the same ones holley still uses. If you haven't done this then afterwards re-adjust your carb's A/F mixture screws. Footage taken from Holley Carburetor Installation & Tuning DVD. The piston travel is altered with a threaded "double-D" screw that is barely seen here (A). On a Holley it's pretty easy to change. You will always want to bring high flow carburetor down to match the low flow carburetor. Remove the tape from the IAC breather hole and restart the engine. This is not ment for the race car guys and is intended for the performance "street" car guys with this issue. Simply turn the screw DOWN ½ turn at a time until you experience a “lean surge”. Carb has recently been converted to E85 with bigger jets & retune the idle circuit. Be sure to read the Holley carb installation instructions that come with the carb and follow them carefully. If you stay in a deeper gear and get her at or abouve 3k - no stumble. That was the end of the subject. new "old stock" carb (told by carb rebuilder it is a 2210 for a old stock chevy) has good mix control and i have it spun out about 3 turns. Carburetor Troubleshooting Guide. We have kits for all of the 1904 carburetors, even some hard to find. It basically allows the automatic transmission and the engine to catch up to a sudden closing of the throttle. There is a small white or pink plastic cam with the accelerator pump arm riding on it. Leave the carburetor in the upside down position overnight. Screw the idle control screws in or out will allow more or less (emulsified) fuel to exit the carb. In the picture in the below link is a Ford spec (1950's) Holley 1904, the SCV is the silver part in the middle on the base of carb. 1:1 carbs need to have proper transition slot exposure and should be equal front and rear. Averaged 14mpg with leadfoot driving. Tuning tips for your E85 carburetor (crazy long) you accelerate from part throttle or idle check the Water temp first, cold engine can and will usually have a. CV stands for CONSTANT VELOCITY, and that's what the slide seeks to maintain. 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. Wide-open-throttle mixture should be adjusted by changing the secondary jets, but only after all other circuits are properly tuned. Just ordered a tuning kit for this carb. Had the same problem with a 670 street avenger. GM 3 bar MAP Sensor part# 12223861. Its a 850 double pumper carb running on a 12. Shop with confidence. So I changed out the quirters from 31/28 to 35 in front and 31 in rear. Tick Performance is proud to be a warehouse distributor for the entire Holley product line. The problem I have with my 63 Impala is what holley calls a "tip in" stumble. 5 for one carb power valves were dumping too much from two carbs and loading it up. Holley secondary stumble Got a stumble when I crack the secondaries on my 650 holley that I'm having a hell of a time tuning out. "When" this occurs is determined by the 'high speed" air bleed (typically in the carb throat near the idle air bleed). I haven't tried the alky carb with low RPM leave yet so no help there. It also acts a little bit sick while coming off plane if I bring the throttle to about 1/2. The single hole job is for a 50-cc pump, while the others are used on 30 cc pumps. Wide-open-throttle mixture should be adjusted by changing the secondary jets, but only after all other circuits are properly tuned. I'm still experimenting with it. Just go up one size at a time untill the stumble disapears. In an 18 foot flatbottom with 18% gears and a 11 1/2" by 15 prop the carbs held 10" of vacuum up to 5500 RPM. Had the same problem with a 670 street avenger. Can you put aEdelbrock Torker 2 intake and holley four-barrel carburetor on my 1990 chevy 1500 5. Holley Carburetor: Idle and Transition Circuit Calibration Guide July 27, 2015 by Muscle Car DiY At the risk of sounding repetitive, let me say once again, that if you bought an application-specific carb, you probably are only going to need to do minimal adjustments to mixture calibration. But as soon as I want to add a little bit of power and have to push past about 50% throttle you can hear+feel the power sower and if you push it to the floor it makes a horrible pop and fart sounds. Rated 4 out of 5 by Modded68SBF from This Holley works great AFTER it is tuned I have had my carb for half a year now and I am still tuning this carb to work since I am running a cam. Which type of discharge nozzle do you use in your Holley? I am in the process of tuning my Holley 670 Street Avenger to my new combo. HGM's AccuLink is a really slick chrome steel conversion package that provides a GM-style TPS sensor to all in style Holley, Q-Jet, and Edelbrock carbs. At part throttle while driving you can hear it stumble for a bit. This is not ment for the race car guys and is intended for the performance "street" car guys with this issue. less than other carburetors. Install all peripheral vacuum and fuel lines, and and baseline adjust all choke linkage(s). New 3-14-01 This tech paper will discuss basic set-up and tuning of Holley vacuum secondary carbs for optimum street performance and drivability. Decided I've messed with that old carb enough. I think the bracket is too far back. Over the last 3 months my 390 cfm Holley gives a big stumble during a left turn out of the driveway. Also, fuel can boil in the carb if there are improper or missing gaskets or spacers between the carb & manifold. Holley supplies a clamp-on bung but I didn't have any straight pipe to do it. It was a nightmare to get it on and off a trailer. The carburetors must return instantly and positively back onto the idle set screws every time the throttle is released. Power valve blown out by spitback up through carb. I have also been assuming that you are running a stock carb and distributor so if your carb dose not have the SCV then maybe you also have a different distributor like an aftermarket hot rod type or other newer. BG carbs (and Holley carbs, too) used in a performance applications need to meter equal air through both primary and secondary sides of the carb at idle. Kendig (later the Predator carb) made a big one, 900+ cfm for race cars. Correct by bending choke lever assembly (bellcrank) away from main body. yes it takes time to tune it , sometimes alot of time to get it right. Also open the throttle blades until no fuel is coming out of the accelerator pump discharge nozzle. Here is what we have tried so far. It is a bit too much carb for a mild mannered street ride. So I changed out the quirters from 31/28 to 35 in front and 31 in rear. This will add timing at part throttle under light acceleration and will often cover up a part-throttle stumble. Holley Part Throttle Cruz Stumble Solved Ok so this is my first post besides the newbe and I'm sure to get a lot of backlash for this, but here goes. Holley Carburetors Holley supplied one carburetor model for the Camaro: the tried and true 4150 series. Whatever you do a vaccuum secondary carb is a horrible choice for racing or any performance driving in my experience. If you haven't done this then afterwards re-adjust your carb's A/F mixture screws. This Holley 1904 carb kit is ethanol ready, made in the US and meets, or exceeds manufactures specifications. Induction Parts Interchange for Small-Block Ford The small-block Ford’s 39-year production life included a broad array of induction systems ranging from the humble 2-barrel carburetor, to high-performance Holleys, to throttle body and port electronic fuel injection systems. Fresh rebuild, no other issues except the following. Holley Carb Float Adjustment Fuel Level How To Adjust Tutorial Instructions Side Center Hung - Duration: 4:21. Third, TMP manufactures an adapter to place the Holley carburetors right over the carb pad / flange which also provides attachment points for throttle linkage. If you are hunting for Holley Volvo Penta Boat Parts, you have come to the proper place. Holley carburetor tuning guide ( 4150 Carbs ) Part 1 - Duration: 10:57. In general, carburetors with divorced chokes use a separate choke-pulloff to open the choke. I have a 65 Chevy C20 with a 327 from a 66-67 Impala, that originally had a Holley 4160. There were no other boats out so I had a looong walk back with boat in tow until the fuel had dried up enough for the engine to fire up to get us back to the slip. Now that we have a good understanding of the tools available, let's take a look at what we're trying to achieve. It has a Performer intake, CH-4B old school. Integral chokes have a piston inside the choke housing. & I at first went back toward the blue and white cam,. Very few enthusiasts truly appreciate just how much a functioning vacuum advance helps drivability. At wide open throttle, check to be sure that. Remember, primary jets and metering rods will affect steady cruising and part-throttle operation. If the carburetor is supplying too lean of an air/fuel mixture, the engine will lack power, run sluggish, overheat and the lean mixture could cause engine damage. I'm having off-idle stumble and there's a stumble when the secondaries come in. Carburetor Parts And Components Holley offers a wide variety of replacement and performance enhancing components for your Carburetor. The 2280 was part of Holley's "Economaster" line, and had some odd vanes in the booster venturis that aided fuel atomization. We have kits for all of the 1904 carburetors, even some hard to find. I am currently looking at purchasing a new carb. If the trailer is dragging (like one of the wheels is in a small hole), the engine stumbles. ’71 ‘Cuda with 440 6 Pack "I bought 2 POWERBLAST PLATES for my 4150 Holley carburetor in my '67 Camaro. Lateral G force has to be fairly extreme to cause a stumble, but Holley did develop center hung float bowls for road races, where side hung float bowls like those on Truck Avengers suffered fuel level problems. No exceptions to this rule. Eric calls his carburetor a Heinz 57 because it is a mix of all sorts of different parts. The primary side is the most used and has the idle adjustment that feeds fuel from below the throttle plate. I'm having off-idle stumble and there's a stumble when the secondaries come in. Wide-open-throttle mixture should be adjusted by changing the secondary jets, but only after all other circuits are properly tuned. Everytime you let off the gas and pick it back up and stumbles and runs like dump. I have also been assuming that you are running a stock carb and distributor so if your carb dose not have the SCV then maybe you also have a different distributor like an aftermarket hot rod type or other newer. CV stands for CONSTANT VELOCITY, and that's what the slide seeks to maintain. yes i know that THEY SAY a power valve plugged carb will run rich at part throttle, but YOU also know with all of the other carb tuning basics, a timing light, and valve adjustment and an ignition system and stall a calculator a vacuum cleaner and a hair drier you can definetly get rid of it. I've set float 4 different heights, no change. This system is one of the reasons Holley carburetors are so tuneable. It is much more of a problem on a carbureted car. The dizzy is a Mallory Unilite with Pertronix & vacuum advance and the timing has been set all over the place - currently it's about 12 degrees initial. Once its stuck grab the secondary linkage and push it closed. Ensure the carburetors are pushed all the way to the rear of their mounting studs. 5 and timing is 36 @ 3000. Sure enough, had a stumble or flat spot with "new" carb installed. A better description of the symptom would help us to ascertain whether the accelerator pump circuit or transfer slot is the problem. We show you some tips and give the step by step details on how to rebuild one for your mill. Barry Grant Just Made Idle Speed Tuning for Big Cams Easy. I have also been assuming that you are running a stock carb and distributor so if your carb dose not have the SCV then maybe you also have a different distributor like an aftermarket hot rod type or other newer. Clearly there are other issues going on, but the lack of vac advance is very likely adding to it. In Carb Tuning Tips, Part 1, we provided a brief overview of the carburetor, including some basic carburetor anatomy. I'm not sure I want to go to a 4500 stall converter that will create a lot of excess heat with most of my driving under 3,000 rpm's. The primary side is the most used and has the idle adjustment that feeds fuel from below the throttle plate. > Tuning a Vacuum Secondary of a Holley Carb Tuning a Vacuum Secondary of a Holley Carb June 20, 2017 Randy Bolig Drag Race 101 , General Engine , How-To and Tech Tips , Slideshow , Tech , Tech Tips 1. Just go up one size at a time untill the stumble disapears. Just about anything under 3k will stumble intermittantly if I leave the throttle in the same position long enough. The bog or hesitation may be caused by a momentary lean condition when the carb goes from the idle throttle position to the main metering system. You could rebuild the carb and hope that takes care of the problem. Light Throttle Stumble Holley Trash Or Be Trashed. The new carb we ordered for the 2000 was a different number. Note 1: often removing the carb from the manifold & shaking it hard a couple of times will effect a cure. No exceptions to this rule. JEGS Performance 84,516 views. To do this, flip the carb upside-down and adjust the primary and. Conventional opinion seems to be love/hate regarding the thermoquad. Re: Serious engine stumble with 3. 18 initial 34 total timing. The last two numbers are the size of the rods. Find Holley Street Avenger Carburetors 0-81670 and get Free Shipping on Orders Over $99 at Summit Racing! Holley's Street Avenger 4-barrel carbs offer trouble-free operation in an easy-to-install package. Hesitation under heavy throttle: Deadspot & stumble. Holley carburetor tuning guide ( 4150 Carbs ) Part 1 - Duration: 10:57. If the adjustment is to be made off the engine, open the throttle valve and move the choke to its closed position. Plugging PCV saw no change, nor did spraying at the intake gasket against the head. Anyway, thanks for replying. This is seldom set correctly on an out-of-the-box carb. I tried part-throttle and full-throttle stabs at different rpm's from 2500 to 3000. 5 and timing is 36 @ 3000. That plus the super-clean plugs make me think its lean on idle and light throttle. If you experience a bog or hesitation off idle, you can try a higher # (larger) shooter size. 4200 stall and 4. If carburetor has fuel inside turn upside down over a proper container, tilting and tipping the carburetor slightly, back and forth to remove as much fuel as possible. From replacement fuel bowls to power valves and jets and everything thing in between. Assorted Carburetor Parts for Holley & Edelbrock Carburetors. *Holley 4150 750 Double Pumper, model 4779 Timing all in at 36, 18 initial, 10 in the vac can. Re: Holley 750 Stumble at Cruise are you describing a surge or a tip-in/slight throttle? If it's a steady speed surge I would lean towards working the idle feeds. Keep in mind that you will need to re-adjust the accel pump lash adjustment after you bend the arm. I had one from a Holley carb. New original equipment carburetors and new aftermarket service replacement units. Different carburetor systems use different parts to adjust or tune these areas. 4) No power or heat source to choke. Sure enough, had a stumble or flat spot with "new" carb installed. Finally got back at the carb today but didn't make any progress. Re: Holley 750 Stumble at Cruise are you describing a surge or a tip-in/slight throttle? If it's a steady speed surge I would lean towards working the idle feeds. Pull it toward the front of the truck. This is a really bad aspect of the Edelbrocks, IMO for those of us in hot climates. All modular (4150, 4160 and 4500 series) Holley carburetors place the idle feed restrictor in the main metering block. But as soon as I want to add a little bit of power and have to push past about 50% throttle you can hear+feel the power sower and if you push it to the floor it makes a horrible pop and fart sounds. The brass pin is shoved in all the way so it totally blocks the hole. Secondary jets are the same as used in traditional style Holley carburetors. Carburetor Parts And Components Holley offers a wide variety of replacement and performance enhancing components for your Carburetor. You are not a full throttle yet, so now the butterfly is directing globs of unatomized fuel to one end of the manifold. Remember, primary jets and metering rods will affect steady cruising and part-throttle operation. On a Holley carb, check float levels too. You need the Holley spring loaded rubber-tipped float needles, part number 510-6-513 in the Jegs catalog. Shop with confidence.