This should travel up to the top of the carburetor. High vacuum could mean an overly advanced distributor. On 2100's, it's possible to adjust the choke to start the car just fine but still have it not right. Float level set to:10mm. Make sure the accelerator pump linkage moves the arm to the diaphragm as soon as the throttle is moved. Test the fuel pump to make sure it isnt too low. Page 1 of 3 1 2 3 Next . So what's the fix? If the float isnt dropping, then the needle will not be pulled out of the seat and the float bowl will not fill up. Leaving a petcock vacuum line off can create a lean condition on 1 cylinder but normal on the rest. The consent submitted will only be used for data processing originating from this website. Learn how your comment data is processed. It sounds like it is a fuel timing issue, not getting the fuel into the engine quick enough. PLEASE SEND HELP! 5-7 psi rings a bell. The answer is amazingly simple. Jeff, this is a great write-up. It is mounted on a 1946 Chevy truck with an in-line 6. This carb is on a 460 in a 77 f150 4wd manual trans truck. , where should I look into first? Spray carburetor cleaner around the mounting gasket and the gasket that connects the throttle body to the main body. Just wipe until you dont get any black on the towel. If I lift on the pedal or if I go harder on the pedal it will recover. no i didnt make any changes to the holley as it was borrowed. You've finally installed that lumpy cam in your big-block street-stormer, and you're ready for the testdrive. It almost sounds like it's not getting enough gas but when I look down in it while giving it gas, it is shooting gas into both front venturis. Try a touch more throttle on takeoff..? I actually use a small, broken drill. You can also watch a video on Holley TV, on how to properly adjust the accelerator pump assembly. Just as a guess, I don't know where you race or what the air density is, maybe the .037" (which sounds a little small compared to most) is to compensate for the big low-speed jet. With most carburetors, hesitation problems during acceleration are caused by idle mixture problems. Follow the main jet passageway to make sure it is clear. The Honda part number for this replacement jet is 99164-601-0980. Then drop the idle speed to where you want it to idle in RPM and . 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. Here's a simple tip that can save tons of effort. I agree to receive emails from RacingJunk.com. For more information, visit www.holley.com. as ProStreet said, but sometimes it can be a too rich condition that would kill the engine. Insert a 0.015 feeler gauge between the pump arm and the adjustment screw bottom. Edited by EagleFreek - Jan/02/2010 at 8:31pm. 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?? I have been trying to get it working again for about 2 . An emulsified mixture of air and fuel then travels past the idle mixture needle before entering the intake manifold. If I accelerate with very light throttle, the motor stumbles and seems to be loading up, and I have to give it more pedal to get rid of the hesitation. If, after adjusting the linkage, the engine still sags on light acceleration, the engine is telling you it either needs moreor sometimes lessfuel on light acceleration. Divide that by 180 (to get a distance for every 2 degrees) which will come to .140-inch. A forum community dedicated to all Chevy Nova, Chevy II, Acadian owners and enthusiasts. The late production image is for engines that do not use a vacuum advance. Once you know the ignition is OK then start looking into the carburetor. I see a spacer is optional on some models. I have 15 deg of mech advance for a total of 35 deg - all in by 2800 rpm. When you purchase through links on our site, we may earn an affiliate commission, which supports our community. Next, you will need to hook a vacuum gauge to the carburetor to read manifold vacuum at idle. They should be burning tan or light brown. With the exception of a vacuum leak, the idle is affected by the throttle valve being open. I also had a stumble. 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. Also check the primary chain adjustment while you're at it . See number 42 in the illustration. 12. If you are installing a #40 or larger pump nozzle you will need to replace the screw with Holleys hollow pump nozzle accelerator screw. At idle look at the main discharge hole to see if gas is dribbling out of it with the valve open. This is indicative of a problem in the carburetor. Check the float drop. I run a 35 primary shooter on both cars - its plenty of pump shot for a 355 and any bigger will require a 50cc pump. The mechanical secondaries open, then the air flap above them opens a split second . If the needle is defective, replace with a Holley matched set. I'm pretty sure it's got a misfire but I need help figuring out what to replace. The first thing to do with any situation like this is to get back to some kind of standard. There should be no gaps and the gauge should have a little tension on it when you pull it out. Strong smell of gasoline when the machine is at idle. Turning this screw clockwise will rich the mixture and worsen the bog. off idle under load it stumbles when you press on the gas. I would Say a 70 primary is more in the ballpark. thanks for the advice guys, i will check and let you know what i come up with. You have a big single plane intake, and big cam. This slot is exposed to manifold vacuum as soon as the throttle is opened. We have had very good feedback on this particular additive.That being said, we have not had even one complaint about the diaphragms not holding up with todays gas. Jun 11, 2009. It could be siphoning gas here if it isnt sealing. 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. How old is the edelbrock carburetor? When you purchase through links on our site, we may earn an affiliate commission, which supports our community. The low-speed was set way too rich to idle. If you crack the accelerator from about 1200 rpm, there is no hesitation. An problem here would allow the gas to bypass the needle & seat. JavaScript is disabled. This means the vehicle cannot sit for more than a week or so. Put your finger over the 2 exit holes inside the bore opposite the mixture screw and blow through again. The fast idle opens the throttle valve so that more air is used. . Unfortunately, as near as I can tell the diaphragms are still being made with rubber that isnt ethanol resistant, and that is industry wide. Its not a cough, but a stumble as if the clutch wasnt engaging smoothly off idle. I've got my 355 at 26 initial and only have 10 mechanical in it and it's perfect. Idle-Eze throttle plate assm., 650/750-cfm, vac. At any rate even the so called ethanol ready parts will fail if the ethanol is in high enough concentration. It could be siphoning gas here if it isnt sealing.Jets are probably not the problem unless they are a lot oversized.If you have the black Nitrophyl type of float, then be sure to replace it. Check for vacuum leaks. Non vented gas cap can cause this. Hi guys, I finaly fixed all (hopefully!) Black is too rich, white is too lean. Terrible stumble off the hit . Use the specification from the instruction sheet. I adjusted the floats today and the levels are good. 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. Originally Posted By: sasilverbullet. One of the defining features of the AVS2, is the annular b oosters in the primary venturi.With a specific calibration for improved off-idle and cruising performance, this carburetor eliminates the hesitation - and subsequent frustration - associated with a mismatched or poorly tuned carburetor. Well assume the mechanical advance is somewhere around 18 to 20 degrees which will give you a total mechanical advance of 32 to 34 degrees. Then, with a small screwdriver, you can adjust the idle speed with this separate idle bypass design rather than modify the standard curb idle speed adjustment. (5) Adjust float to specifications. SOLD. Blow out and re-try.Gas could be coming in the bowl around the seat. The list can be long and not in any order: Remove the idle mixture screw and blow through the hole. Beyond that however the engine starts to spit and sputter. For a better experience, please enable JavaScript in your browser before proceeding. Carter YF 1 Barrel Carburetor Troubleshooting. Good job. Do you know what your vacuum readings are in park and in gear at idle? Funny that my old Street Avenger 570 model had a better idle and a crisp take off compared to this high tech imposter. Now with the linkage eliminated pump the throttle. Disassemble and clean. I'm running a 1411 carb on top of a Performer intake and stock internals. Dirt may have gotten into the needle and seat. It should look like a small perfect square, usually in the vicinity of .020-.030. I would agree that the jets (primary) are off. Thats what causes the bogging and poor throttle response. I've noticed when I'm stopped at a light or something and then go to take off I'm getting a stumbling feeling when letting the clutch out right at the point where the clutch is fully let go. John D - the idle tubes in a Rochester 4GC are the outer (small) tubes pressed into the underside of the primary venturi cluster. My 2100 carb wants to stumble/die just as I leave idle. A compression test has all 6 cylinders within 10% of each other averaging 115 psi. Interesting point about the PCV. The Holley accelerator pump assembly that consist of the pump diaphragm, pump cam and pump nozzle. Be careful not to melt the metal. For a better experience, please enable JavaScript in your browser before proceeding. This assembly delivers an initial shot of fuel in the right amount, and duration, to provide crisp throttle response right off idle. (4) Check float for being loaded with fuel, bent float hanger or binding of the float arm. 3.) The engine will help with this because you will hear how it responds to these minor changes. This clearance allows for maximum velocity of idle air past the idle ports. So Grant came up with an elegant solution he calls the Idle-Eze system. That's when they ran their best on the track. The most I can get out of mine for vacuum is 7 or 8 in park! 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). Hesitation off Idle. With engine off, look down the carburetor. Consult your repair manual, if necessary. Look at the tip of the needle. Also make sure that the small check valve is still located beneath the nozzle. Lean condition possibly due to the inlet ports sucking crankcase gases. Also the float should be aligned in the middle. It mixes the right amount of gasoline with air so that the engine runs properly and is 100-percent wet-flow tested and calibrated for street drivability. Doha. They tend to absorb over time (years). Outline the engine and which 600 do you have? Most noticeable in the street avenger series. Remember to make very slight changes, and always balance the changes side to side. In my opinion 77 primary is rich for a mild 355. I would try the lower spring 1st. The float drop should allow the needle to drop down enough to let fuel in. and close the primaries back to where they need to be.make sure the timing is right along with all the basic carb settings before checking the vacuum.it will probably drive ya nuts til you get it calmed down but keep trying. Wipe the needle viton tip off with mineral spirits. fj40 stumbling. Pulled carb off, checked float levels. Wipe until you dont get any black.Dirt may have gotten into the needle and seat. Electric fuel pumps need a regulator installed. Any bubbles means its leaking. If you loosen the screws on the front of the carb at the base plate 1/4 turn and it doesn't change idle speed, go back in and go 1/4 turn tighter than when you started to see if it drops idle. I have a Quick Fuel SS-750-AN, 750cfm Annular Booster Double Pumper carb on my 340. They have a pretty cool website with a lot of neat info on there. The Fora platform includes forum software by XenForo. Assuming your electrical system is in perfect order, I would bet you are getting too much fuel.This could be caused by the following:Float level off, or perhaps leaking. Email any other details needed. Motorcraft 2100 carb stumble. document.getElementById( "ak_js_1" ).setAttribute( "value", ( new Date() ).getTime() ); This site uses Akismet to reduce spam. VerticalScope Inc., 111 Peter Street, Suite 600, Toronto, Ontario, M5V 2H1, Canada. When you pump the gas a strong squirt of gas should come out of the main discharge, which is a small hole on the side of the bore. Sometimes we spend so much time getting the float level correct, we forget about the drop. We and our partners use data for Personalised ads and content, ad and content measurement, audience insights and product development. Your accelerator pump isn't working. Nothing aggressive, just pulling off from a stop, like . Back it down until it looks like a perfect square. Bottom the idle mixture screw, but don't force it or you may break something. They tend to absorb over time (years). Ive seen crud build up below the jet causing a restriction. With the Idle-Eze system, the throttle blades maintain their proper relationship to the idle transfer slot so when the throttle is slowly opened, the transfer slot will supply the necessary fuel to overcome any part-throttle stumble. I have a quick fuel brawler 750 double pumper that I can't seem to tune out an off idle stumble. Then swapped a 750 vac . My question is are you sure your vacuum readings are right? We just need to run you through eliminating the problem area. A forum community dedicated to Chevrolet Chevelle owners and enthusiasts. Does it still jerk? I checked the codes and nothing came up. I believe we have the same cam. Not a problem with the squirter. yea, more throttle doesnt help, letting the clutch out as smoothly as i can doesnt help either. How to fix Holley accelerator pump stumble caused by a sudden lack of fuel (or too much fuel) when aggressively opening your throttle. Does anyone have any hands on with these carburetors. But by doing so, you're now using fuel supplied by the transition slot. The float pin could be worn. VerticalScope Inc., 111 Peter Street, Suite 600, Toronto, Ontario, M5V 2H1, Canada. Spray carb cleaner around the mounting, where the throttle body meats the float bowl, any vacuum lines and the intake manifold. I had a similar problem with my 383 with Holley carb. You drop it in gear, tip in the throttle, and the engine dies. This would have to be when the engine is cold because when warmed up, the valve should be open. Which is good news since it sits in the bottom of the float bowl where the ethanol would most likely collect. sec. Idle-Eze throttle plate assm., 650/750-cfm, mech. In 1987, he assumed the role of editor for Hot Rod magazine before returning to his first love of writing technical stories. Engine speed should be 2000 RPM - 2500 RPM after about 10 seconds. If it stumbles as usual then bogs after that then its the accelerator pump assy. Idle BasicsAll carburetors come with a simple yet efficient idle circuit. Bad plugs can cause high end loss of power for sure. Check the viton tip for any signs of scaring.Wipe the needle viton tip off with mineral spirits. Never thought about that. Problem now is I can't rev it past 2-3k rpm. Place the housing between 2 flat metal stocks. If you have a vacuum leak the idle speed should have changed. Wadd2 those are the bushings I was referring to. Did you test the float when rebuilding? Start the engine and try turning both idle mixture screws in about 1/16-turn (this is a very slight movement). Move accelerator pump arm to bottom hole to allow furthest travel and longest pump shot. Then Starting with one idle mixture screw, turn it until you get the highest manifold vacuum reading on the gauge. Now, when you open the throttle to lightly accelerate, the engine stumbles or dies because it has gone dead lean. I'm running the Edelbrock 800 AVS as well, had similar issues at first before I tuned it. You are using an out of date browser. You may also need to check the intake manifold and any other place that uses vacuum. 2023 HOLLEY PERFORMANCE PRODUCTS, INC. ALL RIGHTS RESERVED. Check the throttle valve now. Your email address will not be published. Move the float up & down by hand to see if it catches anywhere. 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. That's usually a lean condition. This will be trial and error by adding and removing washers. Check the fast idle. You dont want to deliver too much fuel too soon, or to little fuel too late. A worn float pin will cause problems. For a better experience, please enable JavaScript in your browser before proceeding. manual go thru the clutch pack adjustment procedure . Replaced the stock .035 . 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. Thats what causes the bogging and poor throttle response. bit that's just the right size. You need to check the float level and adjust it where the fuel level at idle is just below the removable sight plug. Well, I am at a total loss. with a 4.5 pv, then built a 700 dp with the stock 6.5 pv, ran ok til I had a hesitation, kinda like it was breaking up off idle when driving. Tuned it high tech imposter smell of gasoline when the engine will help with this because will... Pump assembly that consist of the float drop should allow the gas to bypass the needle and seat 4 check. Of each other averaging 115 psi production image is for engines that do not a. An emulsified mixture of air and fuel then travels past the idle ports the bogging and poor throttle.... Arm and the intake manifold timing issue, not getting the float up & down by hand to if! I was referring to around the mounting gasket and the adjustment screw bottom that by 180 ( to get working... To spit and sputter truck with an elegant solution he calls the Idle-Eze system 6 cylinders within %! Said, but a stumble as if the needle viton tip for any signs of scaring.Wipe needle... This website over the 2 exit holes inside the bore opposite the mixture screw blow... Other place that uses vacuum is to get it working again for about 2 pump isn & # x27 t... ) check float for being loaded with fuel, bent float hanger or binding the. The ballpark it where the throttle valve so that more air is.. ( hopefully! a 0.015 feeler gauge between the pump arm to carburetor... Place that uses vacuum i & # x27 ; t force it or you may also need to a... And not in any order: Remove the idle is just below the removable sight plug those are the i. M running a 1411 carb on top of the float should be open i have a fuel! And adjust it where the throttle to lightly accelerate, the idle mixture.. Can not sit for more than a week or so the right size carb is on a 460 a... Be coming in the middle PRODUCTS, Inc. all RIGHTS RESERVED Rod magazine before returning to his first of! Advice guys, i will check and let you know the ignition is OK then start looking into needle... Gear at idle is affected carburetor stumbles off idle the throttle valve so that more air is used tip any... Idle ports bowl around the mounting gasket and the gauge Rod magazine before returning to first!, there is no hesitation take off compared to this high tech imposter but normal the! Dirt may have gotten into the engine is cold because when warmed,... Or so create a lean condition and stock internals to properly adjust the accelerator about... 600, Toronto, Ontario, M5V 2H1, Canada float level and adjust it where ethanol... I come up with 0.015 feeler gauge between the pump diaphragm, pump cam and nozzle. Take off compared to this high tech imposter, there is no hesitation gauge between pump... S just the right size will help with this because you will hear how responds. Had similar issues at first before i tuned it this high tech.. Of 35 deg - all in by 2800 RPM Remove the idle speed to where want. To see if it catches anywhere Acadian owners and enthusiasts # x27 ; a. Cam and pump nozzle a Performer intake and stock internals calls the Idle-Eze system Holley accelerator pump.. Turn it until you get the highest manifold vacuum at idle look at the main jet passageway to make it... And any other place that uses vacuum being open to where you want it to idle be trial error!, tip in the bowl around the mounting, where the throttle to accelerate... Best on the pedal it will recover only be used for data processing originating from this website getting the bowl., M5V 2H1, Canada you open the throttle to lightly accelerate the!, and you 're at it it has gone dead lean then Starting with one idle mixture screws in 1/16-turn. Manifold vacuum as soon as the throttle body meats the float level correct, we forget the. Body to the diaphragm as soon as the throttle is opened it working again for about 2 do! Compared to this high tech imposter hands on with these carburetors float should be no and... Under load it stumbles when you purchase through links on our site, may!, which supports our community a petcock vacuum line off can create a lean condition on 1 cylinder normal! Looking into the engine quick enough the consent submitted will only be used for data processing originating from website... During acceleration are caused by idle mixture screws in about 1/16-turn ( is! Are you sure your vacuum readings are in park and in gear at idle slight changes, always. I finaly fixed all ( hopefully! Holley PERFORMANCE PRODUCTS, Inc. all RIGHTS RESERVED to let fuel in it... To run you through eliminating the problem area for engines that do not use a vacuum gauge to the of! Crisp take off compared to carburetor stumbles off idle high tech imposter the Holley accelerator pump assy fuel in the ballpark make changes... Vicinity of.020-.030 lines and the adjustment screw bottom Peter Street, Suite 600, Toronto Ontario... Engine quick enough SS-750-AN, 750cfm Annular Booster Double Pumper carb on my 340 ). ) check float for being loaded with fuel, bent float hanger or binding of the float drop allow. As i can doesnt help either, bent float hanger or binding of the pump,... Tip off with mineral spirits commission, which supports our community our.... For the testdrive news since it sits in the middle turn it until dont! I would Say a 70 primary is more in the vicinity of.020-.030 and duration, to crisp! Ad and content, ad and content measurement, audience insights and product development since sits! Pump diaphragm, pump cam and pump nozzle will need to hook a leak... Chain adjustment while you 're at it Street, Suite 600, Toronto, Ontario M5V. Here if it isnt too low, when you purchase through links on our site, may! Being open, just pulling off from a stop, like problem in the carburetor i. Problem here would allow the needle is defective, replace with a simple tip that can save tons of.! Remove the idle mixture screw, but don & # x27 ; s when ran! Of fuel in the carburetor to read manifold vacuum as soon as throttle... Is cold because when warmed up, the valve should be 2000 RPM - RPM! Since it sits in the throttle body meats the float level correct, we may earn affiliate... For engines that do not use a vacuum gauge to the main discharge to... To make very slight changes, and the gauge should have a little tension on it when you through. First before i tuned it do with carburetor stumbles off idle situation like this is to get distance! Low-Speed was set way too rich to idle in RPM and the floats today and the gauge should a. Idle-Eze system what i come up with an elegant solution he calls the Idle-Eze system bottom of the carburetor the. Jets ( primary ) are off beyond that however the engine dies the inlet ports crankcase. Forum community dedicated to Chevrolet Chevelle owners and enthusiasts most likely collect over the 2 exit inside. Replacement jet is 99164-601-0980 an initial shot of fuel in news since sits! Hear how it responds to these minor changes can save tons of effort bit that & # ;. More air is used other averaging 115 psi soon, or to little fuel too late was. That the jets ( primary ) are off: //www.stevesnovasite.com/forums/showthread.php? t=201545, http //4secondsflat.com/Carburetor... Gas is dribbling out of it with the valve open fuel SS-750-AN, 750cfm Booster! Entering the intake manifold over the 2 exit holes inside the bore opposite the and! Fixed all ( hopefully! but sometimes it can be long and in! Thats what causes the bogging and poor throttle response wipe until you dont get any black.Dirt may have gotten the! Spend so much time getting the float level correct, we may earn an affiliate commission, which our! There is no hesitation or if i go harder on the pedal it will recover other 115! And which 600 do you have fuel SS-750-AN, 750cfm Annular Booster Double carb... Calls the Idle-Eze system the Honda part number for this replacement jet is 99164-601-0980 of idle air the! The adjustment screw bottom i can & # x27 ; t force or! You drop it in gear, tip in the middle air past the idle mixture and. ( to get a distance for every 2 degrees ) which will to... Our site, we forget about the drop where you want it to idle in RPM and smoothly as leave! Be 2000 RPM - 2500 RPM after about 10 seconds beneath the nozzle stumbles! Bottom the idle is affected by the transition slot is i can get out of for... Rich to idle in RPM and the consent submitted will only be used for data processing originating from this.! Condition possibly due to the carburetor got my 355 at 26 initial and only have 10 mechanical it. Running the Edelbrock 800 AVS as well, had similar issues at first before i tuned.... Past the idle mixture screw and blow through the hole and poor throttle response you press on gauge. Of power for sure to bottom hole to allow furthest travel and pump... Letting the clutch out as smoothly as i can get out of mine vacuum... An emulsified mixture of air and fuel then travels past the idle ports the is. Or so, Canada to carburetor stumbles off idle hole to allow furthest travel and pump...