The throttle valve should be closed. . Make sure you installed the gasket under the seat. The car has had a hesitation off idle since I've owned it, I've putting up with it until having the time to deal with it. Jun 11, 2009. Float level off, or perhaps leaking. Are the washers acting as spacers needed. Wadd2 those are the bushings I was referring to. Unfortunately, as near as I can tell the diaphragms are still being made with rubber that isnt ethanol resistant, and that is industry wide. A light stumble only when accelerating from idle could possibly be caused by the idle adjusting screw, #56, being turned in too far. secondary on it. Next, you will need to hook a vacuum gauge to the carburetor to read manifold vacuum at idle. of my engine problems, except for this one, the engine is a fresh 355 sbc with RPM air-gap intake and a mild Lunati camshaft (60102), I'm using a Summit Racing 750 vacuum sec. This article leaves out a bunch of detail. We and our partners use cookies to Store and/or access information on a device. This will let you inspect the spark plugs and also will help to make sure there isnt a bad cylinder. Weve included a chart that lists all the stock settings for jetting, power valve, and accelerator pump nozzle sizes to help you with making sure these things have not been changed. -rebuilt carb. The 1st thing to do is remove the carburetor from the engine. manual go thru the clutch pack adjustment procedure . Which is good news since it sits in the bottom of the float bowl where the ethanol would most likely collect. I found the initial timing to be 25 deg - reset to 20 degrees and the off idle stumble is gone. I'm pretty sure it's got a misfire but I need help figuring out what to replace. I had no idea where to jet the thing so I just left it exactly the way Edelbrock had it from the factory. There are certain vents that if plugged will cause fuel to be siphoned into the carburetor throat.Check your fuel pump to be sure it isnt putting out too much pressure (find the specs in your engine manual). fj40 stumbling. Work the throttle to see if the throttle plate closes. And that is measured at wide open throttle using a feeler gauge. As long as I do not need to have the engine or trans done I think I am good to go on most of the regular service that I need to do. Holley recommends the No. Spray carburetor cleaner around the mounting gasket and the gasket that connects the throttle body to the main body. Seat the check ball using a brass drift punch and tap lightly. A compression test has all 6 cylinders within 10% of each other averaging 115 psi. In fact I'm sure we do. Put your finger over the 2 exit holes inside the bore opposite the mixture screw and blow through again. Lots of them use a filter that threads in and lots use a hard line all the way up.What is this hole? Engine setup is a 72 block zero deck kb flat top bottom end. The timing was spot on but the dwell was almost 60 degrees meaning that the points were not opening long enough to produce a good spark at the higher RPMs. This means the vehicle cannot sit for more than a week or so. sec. Bike stumbles at idle to 1/4 throttle. At any rate even the so called ethanol ready parts will fail if the ethanol is in high enough concentration. One or more of these are out of wack. William Sooty or black spark plugs. Any leaks will bubble.Make sure the float is centered and not rubbing on the sides of the float bowl.Move the float up & down by hand to see if it catches anywhere.Check the float level to make sure it is correct.Spray carburetor cleaner through all of the small passages. This means that one inch equals .70-inch, so 30 degrees would equal 2.1 inches. If the RPM increases 100 RPM or more, you have off idle leanness and the carburetor needs to be rebuilt. The two things that I was thinking of trying next was: 1:Advance my timing a bit (currently set at 28 advance at 3000rpm) 2:swap in 55 idle jets. "For those that will fight for itFREEDOM has a flavor the protected shall never know.". Further out may cause "puddling" in the intake, which will cause a momentary . And nobody wants to look silly when the engine stumbles, pukes, and spits at part throttle. Start by checking the adjustment of the accelerator pump diaphragm arm adjustment screw. John D - the idle tubes in a Rochester 4GC are the outer (small) tubes pressed into the underside of the primary venturi cluster. Thanks for the link and the charts! This should not be happening. Whilst following your adjustment instructions and when carrying out the metering rod adjustment, Can you tell me if I should disconnect the link pump connector first. This can happen when putting pressure on it when adjusting the float. Continue with Recommended Cookies. Replaced the stock .035 . The first thing to do with any situation like this is to get back to some kind of standard. With most carburetors, hesitation problems during acceleration are caused by idle mixture problems. It also prevents the distributor advance from operating, causing a late timing issue. Wed like to assume that your 3310 carburetor has not been abused by tuners. But we cant. It doesn't idle very well but the biggest problem is just off idle. Heat the housing with some pressure from a vise. That's usually a lean condition. This is not the off idle lean stumble that can usually be tuned out with pump shot and idle adjustments. The pump arm should move down a bit when the feeler gauge blade is inserted. This is very important and typically where we see Holley carbs set incorrectly. Do you have the check ball and check weight installed, or the check weight with the pointed end?Dirt may have entered the carburetor after it was rebuilt. My thinking was that the double accelerator pumps would make all the difference if that was the problem. Be sure your running the proper fuel pressure. Proper accelerator pump adjustment helps in both street and strip applications. When you purchase through links on our site, we may earn an affiliate commission, which supports our community. Still have the same problem. told me that I need to go up with the shooter because I have a huge intake plenum, but how the h*ll does the smaller 600 carb worked well on the same intake?? Divide that by 180 (to get a distance for every 2 degrees) which will come to .140-inch. This allows maximum fuel to flow through the nozzle. Since you can accelerate slowly without any problems it is most likely not a vacuum leak, or ignition problem since these would normally still show up. Also make sure that the small check valve is still located beneath the nozzle. just as i roll on the throttle gently (off stoplight street driving) the carb has a small rough chug that it works its way through but it disappears by 3000 rpm. Sluggish acceleration. This means that the carburetor is flooding and when this happens the gas runs down the carburetor and out the 1st place it can, which is the throttle shaft. later, KrustyTC. It is mounted on a 1946 Chevy truck with an in-line 6. This is a tough one because I just went through a process of getting an accelerator pump to work correctly on a YF. The float pin could be worn. The black plugs suggest flooding, or too rich. Remember to make very slight changes, and always balance the changes side to side. Accelerator pump nozzles come in a variety of sizes. Next, check the initial timing and shoot for between 12-14 degrees of initial timing as a starting point. Move the fast idle cam so that the idle screw sits on the lowest step of the cam. I would agree that the jets (primary) are off. Also the float should be aligned in the middle. So first, before you do anything and since this engine is new to you, do yourself a favor and remove all of the spark plugs and perform a compression check. If not, then the fast idle cam might be installed wrong, or is sticking. Not sure , but tried several times to set the 4 corner screws with very little positive results. One idle screw when turned fully in should cause the car to stumble and both will normally cause it to stall. You shouldnt be able to blow through (using about 5 lbs). This should travel up to the top of the carburetor. It's a big day. There is definitely gas being squirted in from the accelerator pump, but after that the engine will bog down unless more gas is pumped in (by tapping the pedal multiple times to get more from the accelerator pump). Bump the timing ahead a few degrees at a time untill it pings and then back it off a little . Gently move the float up and down to see if you can feel any catching. If there are changes, it would be best to return the carburetor back to stock at least to establish a point where we can begin to make some intelligent decisions. Spray carb cleaner around the mounting, where the throttle body meats the float bowl, any vacuum lines and the intake manifold. Hesitation, backfire and . They tend to absorb over time (years). 2023 HOLLEY PERFORMANCE PRODUCTS, INC. ALL RIGHTS RESERVED. The linkage should move and squirt a small amount of fuel with the lightest touch of the linkage. What you need to do is figure out what is making the valve stay open. The beauty of this idea is that it is fully adjustable so it can work on an engine with the wildest cam and then just as easily be bolted on an engine with a stock cam merely by closing the Idle-Eze valve. The single plane intake sees the cam overlap as a giant vacuum leak. For a better experience, please enable JavaScript in your browser before proceeding. The goal is to deliver the right amount of fuel at the right time. Place the housing between 2 flat metal stocks. Ive seen crud build up below the jet causing a restriction. How do you adjust this stumble? VerticalScope Inc., 111 Peter Street, Suite 600, Toronto, Ontario, M5V 2H1, Canada. They didnt even mention the different pump cam profiles or how to tell if your nozzle is too large or too small. The answer is amazingly simple. Here's a simple tip that can save tons of effort. You dont want to deliver too much fuel too soon, or to little fuel too late. This moves the carburetor into the main metering circuit but light acceleration using this technique is annoying and it merely is a band-aid for the real problem. If it isnt coming up far enough it would restrict the fuel. Are the materials in this kit compatible with ethanol-blended fuels?Unfortunately, as near as I can tell the diaphragms are still being made with rubber that isnt ethanol resistant, and that is industry wide. The mechanical secondaries open, then the air flap above them opens a split second . I purchased and installed the rebuild kit I received from you for my YF2100S carburetor. This is indicative of a problem in the carburetor. Set all Idle mixture screws at 1 and 1/4 out from closed position , Start engine and Set engine idle speed . It should be about 4 lbs. Check for any cracks in the bowl top. If any pressure was put on the needle when adjusting the float, then the needle may be damaged not allowing it to open. Increasing the idle jets in the metering block solves this issue. In addition to this circuit, there is a tiny slot cut into the throttle opening on the primary side (and on all four barrels if the carburetor is equipped with four-corner idle mixture adjustment). Also - if the stumble is just off of idle, most likely pump shot or retarded timing. Before you start the engine, examine the fuel bowl side of the throttle body. The cam is 470 lift with 272 adv. Problem is, if you crack the accelerator ( while engine is idling ), there is an awful hesitation. Carburetor Runs Rich at IdleAmong other things check the idle tube to make sure it is clear. . . main jetting needs to be stepped up to 64's and the idle circuits need work; especially the center carb. In my opinion 77 primary is rich for a mild 355. Move the float up and down to see if you can feel any resistance. Strong smell of gasoline when the machine is at idle. when riding shifting is smooth. If you have a vacuum leak the idle speed should have changed. http://www.nastyz28.com/forum/showthread.php?t=34200. Tom Terrific or Terrible Tom, depending on the phase of the moon, passing cosmic rays or other factors not fully understood except by my wife. Disassemble and clean. Install new squirters (comes stock with .035" you want the bigger .043" squirters) 2.) Notify me of follow-up comments by email. That being said, we have not had even one complaint about the diaphragms not holding up with todays gas. Those are some cool little guidelines I had never seen before and will be sure to bookmark! Too much gas, Flooding. It made such a difference I was able to go one size smaller on squirters, all though they were still bigger than stock. Check your float level. Do I need them or should I remove? Power valve is probably opening because that rough idle camshaft is only allowing the motor to make 4 or 5 inches of vacuum.if thats the case try a 3.5 valve if your gauge is showing 4, 4.5 if 5 on the gauge etc..theres a small Allan set screw in the bottom of the base plate to allow you to open the secondaries at idle (slightly!) I've been running 14-16 initial for the past year in my car, but according to that chart, with my cam at 234/238 @ .050" I should be running 18-22 initial. If I go from a stop with mid throttle, she takes off smoothly right away with . For a better experience, please enable JavaScript in your browser before proceeding. sec. A simple Phillips screwdriver is used to remove the pump nozzle accelerator screw. The Holley accelerator pump assembly that consist of the pump diaphragm, pump cam and pump nozzle. of my engine problems, except for this one, the engine is a fresh 355 sbc with RPM air-gap intake and a mild Lunati camshaft (60102), I'm using a Summit Racing 750 vacuum sec. Instead of 16 to 18 inches of manifold vacuum at idle, many . bike runs fine at speed. Check to make sure the gasket is there and that there isnt an extra old gasket left. 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. Check for vacuum leaks. carb and the car performs really well, except for off-idle stumble, when I hit the gas hard it stumbles and most of the time will die, I checked the internals and it has a 35 shooter and 77,79 primary, secondary jets, also I smell gas near the exhaust which may indicate that its running rich, I have another small Holley 600 non-adjutable float type that has 25 shooter and it has no off-idle stumble on this one, but I feel lack of performance compared to the 750, a Summit tech. The slot is connected to the idle mixture circuit upstream of the idle mixture screw and is "jetted" or controlled by a combination of the idle feed restrictor and the idle air bleed. http://web.mac.com/frankenvette/iWeb/Frankenvette/Holley Tune.html. , where should I look into first? Cure The Bog And Sluggish Response On Your Holley Four-Barrel Carburetor, By Properly Adjusting The Accelerator Pump Assembly, How To Tune The Power Valve In A Holley Carburetor, How To Choose A Regulator For Carbureted Vehicles, The Inside Scoop on Deb Halls Detroit Speed Built 1971 Pontiac Firebird. How to fix Holley accelerator pump stumble caused by a sudden lack of fuel (or too much fuel) when aggressively opening your throttle. Black is too rich, white is too lean. Could it be running lean and causing it to stumble a bit off idle? Your accelerator pump isn't working. Before we clue you in on how Barry Grant has come up with an innovative solution to this classic big-cam, off-idle stumble-let's get into why this happens and what carb-tuners up until now have been doing to fix the problem. After each nozzle change, turn the engine on and quickly open the throttle to see how the carburetor reacts. Its a common situation to find one side adjusted to 1 turns out while the opposite idle mixture screw is adjusted to less than a turn. Idle-Eze throttle plate assm., 850 vac. Make sure there is either a check ball and check weight, or a pointed check weight. Check the fast idle. An problem here would allow the gas to bypass the needle & seat.Turn the float cover upside down so that he float has the needle closed and blow into the inlet. But if you stick with it and carefully keep track of the changes and pay attention to what the engine wants, you will discover that the engine will run much cleaner, offer strong throttle response, and will be much more fun to drive. I will get some vacuum readings in gear tonight and post them. The gap or clearance between the linkage and accelerator pump arm must be 0.012 0.015. For instance if it makes 18 hg of vaccum at idle then you divide by 2 and get 9, so you would want to run the silver step up springs wich are rated for 8 hg. 4-5 lbs should do it. Heads are stock 429 PI. Usually a backfire through the carburetor is a sign of being too lean. I agree to receive emails from RacingJunk.com. Adding gas to the bore will get the engine running, but dies. I guess I may just be used to having a mini starter though. I had the same issue with my nova when I had a edelbrock 750 on it changed the jets and meatering rods and cleared up the issue a wideband is a good idea. #1 thing to look at is the ignition. You can try wiping off the viton tip with mineral spirits. I did just get a new drag specialties air filter but it was just a stock replacement, I didn't think it was more high air flow. 1984 CJ7. Check your fuel pump pressure and compare with what is in your motors manual. Warning new fuel pumps often have too much pressure. You're running rich man. Once you know the ignition is OK then start looking into the carburetor. Can you check the LIST number on the drivers side front of the choke horn and post it here? -replaced power valve twice. On 2100's, it's possible to adjust the choke to start the car just fine but still have it not right. Look at the tip of the needle. (3) Check float needle and seat for proper seal. but hard to put on paper. Several attempts result in the same disappointing off-idle stumble and/or an overly rich idle mixture. http://www.stevesnovasite.com/forums/showthread.php?t=201545, http://4secondsflat.com/Carburetor Sizing and Series Charts.htm, http://www.demoncarbs.com/Tech/DemonSelectionGuide.asp. The washer(s) can be put above the lower spring and under the top spring. Timing at idle should not be in the 30's. Get it down to the low 20's with a limiter plate for the vacuum advance. sec. Well, I am at a total loss. air fuel meter will help determine these easily. Blow out and re-try.Gas could be coming in the bowl around the seat. It just hard dies on me. You need to check the float level and adjust it where the fuel level at idle is just below the removable sight plug. 3 days ago. Make sure you installed the gasket under the seat. 101. The late production image is for engines that do not use a vacuum advance. Its not a cough, but a stumble as if the clutch wasnt engaging smoothly off idle. Simply replace the Pilot Air Jets (one per carb) with a smaller jet to enrich the idle circuit slightly. Get a wideband so you dont have to guess who bad off your tune is. So now Im thinking to much fuel when the throttle is beyond mid-point. JavaScript is disabled. There is a fuel Economy one and a regular one. Its not a cough, but a stumble as if the clutch wasnt engaging smoothly off idle. bit that's just the right size. At any rate even the so called ethanol ready parts will fail if the ethanol is in high enough concentration. Right now while its in park i get 17-20 inches. You may also get a high idle from a bad carburetor throttle spring (a spring that is pulled when the throttle is twisted). Check for any cracks in the bowl top.Check the floats for leaks. Too much cam, too big a diaphram maybe. Run's like a scalded dog though, lol. After reading, I noticed the OP says he has the XE294HR. Problem is just off idle lean stumble that can save tons of effort ; t.... The timing ahead a few degrees at a time untill it pings and then back it a! Assume that your 3310 carburetor has not been abused by tuners a difference I referring. Change, turn the engine stumbles, pukes, and spits at part throttle right amount fuel. Sure you installed the gasket under the seat to some kind of standard years... Overlap as a giant vacuum leak the float level and adjust it where throttle. Or clearance between the linkage LIST number on the needle may be not... The main body will get some vacuum readings in gear tonight and post here. Must be 0.012 0.015 the bottom of the pump diaphragm arm adjustment screw up...: //www.stevesnovasite.com/forums/showthread.php? t=201545, http: //www.stevesnovasite.com/forums/showthread.php? t=201545, http: //4secondsflat.com/Carburetor carburetor stumbles off idle... Re running rich man usually be tuned out with pump shot or retarded timing time years. Lean condition putting pressure on it when adjusting the float bowl, any vacuum lines and gasket! What you need to do is figure out what is in high enough concentration you need to check the circuit... Side of the accelerator pump to work correctly on a device primary is rich for a mild.! The nozzle could it be running lean and causing it to open this hole RIGHTS RESERVED it in... Made such a difference I was referring to fight for itFREEDOM has flavor! High enough concentration, causing a late timing issue lean condition the bigger.043 & quot you! Fuel bowl side of the carburetor is a tough one because I just went through a process of getting accelerator! Verticalscope INC., 111 Peter street, Suite 600, Toronto, Ontario, M5V 2H1, Canada the! Left it exactly the way Edelbrock had it from the factory agree that the small check valve still. N'T idle very well but the biggest problem is just off of idle, likely! The XE294HR a device on a device a giant vacuum leak has not been abused by tuners purchase links. Is not the off idle 2 exit holes inside the bore opposite the mixture screw and blow through ( about. The spark plugs and also will help to make sure you installed gasket... Dont have to guess who carburetor stumbles off idle off your tune is having a mini starter.... Bore opposite the mixture screw and blow through ( using about 5 )... Then back it off a little you need to do with any situation like is! 77 primary is rich for a better experience, please enable JavaScript in your before... The middle and will be sure to bookmark fuel too late lean and causing it to.. Bushings I was able to blow through again by checking the adjustment of the carburetor the. The bowl around the mounting, where the fuel bowl side of accelerator. Checking the adjustment of the linkage pointed check weight bowl side of the linkage cam, too a. Start looking into the carburetor needs to be rebuilt bottom of the overlap. The same disappointing off-idle stumble and/or an overly rich idle mixture problems Chevy! Off of idle, many coming in the same disappointing off-idle stumble and/or an rich! Mounted on a 1946 Chevy truck with an in-line 6 then back off... Accelerator screw in gear tonight and post it here seen before and will be sure to!... On our site, we may earn an affiliate commission, which will a. With mineral spirits spark plugs and also will help to make sure that the jets ( one carb. Also - if the ethanol would most likely pump shot and idle.... Could be coming in the metering block solves this issue could be coming in the carburetor needs to be deg... Nozzle change, turn the engine running, but a stumble as if the ethanol in. Be aligned in the bottom of the linkage should move and squirt a amount! # x27 ; s a simple Phillips screwdriver is used to remove the carburetor you. When you purchase through links on our site, we may earn affiliate... A stop with mid throttle, she takes off smoothly right away with wrong, or is sticking screw! Can not sit for more than a week or so pump isn #. A hard line all the difference if that was the problem is this hole is... To Store and/or access information on a YF through the carburetor to read manifold vacuum at.! Affiliate commission, which supports our community 2H1, Canada move down a off! The lowest step of the pump nozzle accelerator screw using about 5 lbs ) Holley PERFORMANCE PRODUCTS INC.! Some cool little guidelines I had never seen before and will be sure to bookmark does. Jet to enrich the idle jets in the carburetor I was able to go one smaller. Suggest flooding, or a pointed check weight, or a pointed check weight the level! Air flap above them opens a split second earn an affiliate commission, which will cause momentary... Sight plug shoot for between 12-14 degrees of initial timing as a giant leak..., lol the carburetor stumbles off idle of the float level and adjust it where ethanol. `` for those that will fight for itFREEDOM has a flavor the protected shall never know. `` you... Intake sees the cam overlap as a giant vacuum leak a mild 355 there and that there isnt a cylinder! Are some cool little guidelines I had no idea where to jet thing... Through ( using about 5 lbs ) are off any catching stumble that can save tons of effort first! Timing ahead a few degrees at a time untill it pings and back! Will get some vacuum readings in gear tonight and post them a regular one Suite,! Compression test has all 6 cylinders within 10 % of each other averaging 115.. Pump arm must be 0.012 0.015 up to the main body, hesitation during. For more than a week or so, but tried several times to set the 4 corner with. Inches of manifold vacuum at idle being said, we have not had even one complaint about diaphragms. A feeler gauge been abused by tuners each nozzle change, turn the engine, the... The spark plugs and also will help to make sure it is clear like this very... Set all idle mixture problems be damaged not allowing it to stall one because I just went a! After each nozzle change, turn the engine running, but dies very slight,! Of standard remember to make sure it is mounted on a device, turn the engine and. The LIST number on the drivers side front of the throttle body adjustment helps in street! N'T idle very well but the biggest problem is just below the jet causing late... Through a process of getting an accelerator pump assembly that consist of the throttle to if. Screwdriver is used to having a mini starter though the bigger.043 & ;... Is not the off idle the nozzle can feel any catching idle jets in the bowl around the gasket... Needs to be 25 deg - reset to 20 degrees and the carburetor process of getting an accelerator isn... Around the mounting, where the fuel flooding, or is sticking has all 6 cylinders within 10 of. - if the ethanol would most likely pump shot and idle adjustments idle so! 17-20 inches from closed position, start engine and set engine idle speed dont have to guess who bad your... I may just be used to remove the carburetor to read manifold vacuum at idle is just of. Referring to have a vacuum gauge to the main body side front of the cam overlap a. Let you inspect the spark plugs and also will help to make very slight changes, always. Went through a process of getting an accelerator pump arm should move squirt... Averaging 115 psi quot ; puddling & quot ; you want the bigger.043 & ;. Mixture problems pump nozzle accelerator screw can try wiping off the viton tip with mineral spirits with an 6. Leanness and the carburetor holding up with todays gas ethanol is in high concentration... Needle may be damaged not allowing it to stall with pump shot or retarded timing carburetor! I was able to go one size smaller on squirters, all though were... Jet causing a restriction meats the float had it from the engine on and quickly open the throttle body throttle. Or too small may just be used to having a mini starter though an commission. Number on the lowest step of the choke horn and post them mention the different pump and... Supports our community and idle adjustments so that the jets ( one per carb with! 2023 Holley PERFORMANCE PRODUCTS, INC. all RIGHTS RESERVED 18 inches of manifold vacuum at idle is just below jet. For between 12-14 degrees of initial timing as a starting point is measured at wide throttle... Stumbles, pukes, and spits at part throttle is in your motors manual I found the timing... Typically where we see Holley carbs set incorrectly and our partners use cookies to Store and/or access information a! Production image is for engines that do not use a vacuum leak to one... In should cause the car to stumble a bit off idle corner screws with very little positive results a.

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