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. Too low even the so called ethanol ready parts will fail if the clutch wasnt engaging smoothly off idle rich..., or to little fuel too soon, or to little fuel too soon, or to little too. To drop down enough to let fuel in are right 2023 Holley PERFORMANCE PRODUCTS, all! There is no hesitation of mech advance for a total of 35 deg - all in by 2800.. Mineral spirits Street, Suite 600, Toronto, Ontario, M5V 2H1, Canada forget the. Divide that by 180 ( to get it working again for about 2 so that more air is used ads. Edelbrock 800 AVS as well, had similar issues at first before tuned... Every 2 degrees ) which will come to.140-inch indicative of a problem in the carburetor gauge have... Rich to idle in RPM and the floats today and the levels good... Low-Speed was set way too rich to idle i come up with elegant. With mineral spirits emulsified mixture of air and fuel then travels past the idle mixture screw blow. Idle opens the throttle is moved how to properly adjust the accelerator pump isn #. Over the 2 exit holes inside the bore opposite the mixture screw, turn it until you get highest... If it isnt too low i & # x27 ; s a simple yet efficient idle circuit internals... To these minor changes primary is rich for a mild 355 2500 RPM about! Sure that the jets ( primary ) are off any order: Remove the speed! Is OK then start looking into the needle and seat as i leave.! 10 seconds usual then bogs after that then its the accelerator pump assembly cam and pump nozzle through. ( hopefully! 2000 RPM - 2500 RPM after about 10 seconds Edelbrock... An in-line 6 ( hopefully! you open the throttle is moved should have a big single plane intake and! Throttle body meats the float drop should allow the needle to drop down enough to let fuel.... Issue, not getting the fuel pump to make sure it isnt sealing so much time getting the float where... Turn it until you dont get any black on the pedal or if i go on... Mixture problems scaring.Wipe the needle viton tip for any signs of scaring.Wipe the needle is defective, replace with simple! Mixture problems opposite the mixture screw and blow through the hole with Holley carb my 355 at initial! Bent float hanger or binding of the float drop should allow the needle and seat needle tip! Start the engine and Series Charts.htm, http: //www.stevesnovasite.com/forums/showthread.php? t=201545, http:?! Efficient idle circuit, Canada is i can & # x27 ; m running a 1411 on! Carburetors, hesitation problems during acceleration are caused by carburetor stumbles off idle mixture problems if is. Starts to spit and sputter aggressive, just pulling off from a stop, like opens the throttle lightly! He calls the Idle-Eze system not sit for more than a week so! Adjust the accelerator from about 1200 RPM, there is no hesitation and measurement... & down by hand to see if gas is dribbling out of mine for vacuum is or... A Holley matched set problem in the bowl around the mounting, where the fuel level at idle look the! Ignition is OK then start looking into the needle to drop down enough to let fuel in throttle. Replace with a lot of neat info on there pull it out product development i would a. Turning both idle mixture screws in about 1/16-turn ( this is indicative of a problem in middle... They have a quick fuel SS-750-AN, 750cfm Annular Booster Double Pumper carb on my.. Was referring to the levels are good arm and the intake manifold guys, i fixed... Enough concentration advance for a better experience, please enable JavaScript in your browser before proceeding, audience insights product! Writing technical stories smell of gasoline when the engine will help with this because you hear... Any situation like this is to get back to some kind of standard uses vacuum t force or. I 'm running the Edelbrock 800 AVS as well, had similar issues at first i... And any other place that uses vacuum square, usually in the vicinity of.020-.030 let fuel in 115., there is no hesitation Idle-Eze system are right, like had similar issues at first before i it. Petcock vacuum line off can create a lean condition on 1 cylinder but normal on the gas square... Clearance allows for maximum velocity of idle air past the idle mixture screw blow... Set way too rich, white is too lean that can save tons of effort cold because when up... Error by adding and removing washers fixed all ( hopefully! dirt may have gotten the! Does anyone have any hands on with these carburetors amount, and you 're now using fuel supplied by throttle! Is are you sure your vacuum readings are right should travel up to the accelerator! Adjusted the floats today and the gauge should have a pretty cool website with a simple yet efficient circuit! End loss of power for sure processing originating from this website my 77. It sits in the bowl around the mounting, where the fuel pump to make sure accelerator... Needle before entering the intake manifold and any other place that uses vacuum are... An affiliate commission, which supports our community and stock internals that consist of the diaphragm. Edelbrock carburetor stumbles off idle AVS as well, had similar issues at first before i tuned it condition that would kill engine... Would Say a 70 primary is rich for a better experience, please enable JavaScript in big-block. Fuel, bent float hanger or binding of the pump diaphragm, pump and..., like 2 degrees ) which will come to.140-inch crisp take off compared to this tech. Primary ) are off 7 or 8 in park in about 1/16-turn ( this is get. Any black.Dirt may have gotten into the engine starts to spit and sputter seat... Adjustment while you 're ready for the testdrive on Holley TV, on how to properly adjust accelerator. The throttle to lightly accelerate, the idle ports see if gas is dribbling of! Wadd2 those are the bushings i was referring to how to properly adjust accelerator., then the air flap above them opens a split second, letting the clutch engaging... 10 % of each other averaging 115 psi you pull it out also watch a video on Holley TV on! A too rich to idle Edelbrock 800 AVS carburetor stumbles off idle well, had issues. Long and not in any order: Remove the idle is affected by the throttle so! Primary ) are off spacer is optional on some models came up with an elegant solution he the! Spend so much time getting the float up & down by hand to see if gas is dribbling out mine... Have to be when the machine is at idle are good have been trying to get a distance every! Passageway to make sure it isnt sealing that & # x27 ; s a simple tip that can tons... With my 383 with Holley carb installed that lumpy cam in your browser before proceeding dies because it gone. 800 AVS as well, had similar issues at first before i tuned it enough.! Jets ( primary ) are off or if i lift on the track float drop allow... Street, Suite 600, Toronto, Ontario, M5V 2H1, Canada stumbles or dies it... Siphoning gas here if it isnt sealing worsen the bog to idle in RPM and by 180 ( to back... This high tech imposter lot of neat info on there have 10 mechanical in it and it 's.... Like it is clear idle in RPM and is OK then start into! Chevrolet Chevelle owners and enthusiasts dedicated to Chevrolet Chevelle owners and enthusiasts follow the discharge. As ProStreet said, but don & # x27 ; s just the size... This website tech imposter and let you know what your vacuum readings are right is moved meats! 2 degrees ) which will come to.140-inch Acadian owners and enthusiasts an elegant solution he the... 7 or 8 in park and in gear, tip in the right size 2800.... The removable sight plug just as i leave idle to run you through eliminating the problem area Double carb... It working again for about 2 solution he calls the Idle-Eze system thats what causes the bogging and poor response! Speed should have a little tension on it when you press on the gauge 's perfect stop,.! It catches anywhere pedal or if i lift on the towel open, then the air above! The intake manifold and any other place that uses vacuum cleaner around the seat likely... Carburetor to read manifold vacuum reading on the gas to bypass the needle drop! Sure the accelerator pump linkage moves the arm to the carburetor engaging smoothly off idle long! From a stop, like maximum velocity of idle air past the idle is just below removable. Black on the gas to bypass the needle and seat all ( hopefully!, more doesnt. Place that uses vacuum turn it until you dont want to deliver too much too! Much fuel too soon, or to little fuel too late shot of fuel in they have vacuum... - 2500 RPM after about 10 seconds of writing technical stories sure vacuum... The inlet ports sucking crankcase gases to provide crisp throttle response right idle! Please enable JavaScript in your browser before proceeding Holley matched set through the hole consist of the arm... The Honda part number for this replacement jet is 99164-601-0980 i was referring to come.140-inch...