If they are way off, thats good. Jun 11, 2009. Part throttle hesitation (going from light acceleration) 3.) No carb heat will cause an off-idle stumble and driveability issues every day of the week, unless pump shot and primary jets are made unnecessarily rich. The metering rod seems to be in place. I actually use a small, broken drill bit that's just the right size. JavaScript is disabled. http://i2.photobucket.com/albums/y34/kcwrrn/Wheels001.jpg, http://i2.photobucket.com/albums/y34/kcwrrn/100_0298.jpg, http://www.aedperformance.com/Tuning Tips.htm. First, make sure that the fast idle cam lever is disengaged so that the operating lever opens all the way. Start the engine and try turning both idle mixture screws in about 1/16-turn (this is a very slight movement). We transferred the new Edelbrock intake and carb to the new engine. Join. This can be fixed by doing a rough adjustment. That cam should lower the dynamic compression a little. Too much gas, Flooding. . Idle-Eze throttle plate assm., 650/750-cfm, mech. If you have a carburetor that has the vacuum advance port, plug it with a 1/8 pipe plug fitting. There is like no resistance while turning the air screws. Check the fast idle. If it has enough overlap for a loping idle, fuel injection wont have enough vacuum to not be a pain in the butt to tune. When you purchase through links on our site, we may earn an affiliate commission, which supports our community. 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. I believe we have the same cam. 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. Spray carburetor cleaner around the mounting gasket and the gasket that connects the throttle body to the main body. High vacuum could mean an overly advanced distributor. To narrow it down, tap the roll pin out of the accelerator pump lever by using a small pin punch or a small finish nail. i preferred a .025" squirter with tubes and a white 218 pump cam when i was running 6paks. I agree to receive emails from RacingJunk.com. Hesitation off Idle. Does it still jerk? . Then Starting with one idle mixture screw, turn it until you get the highest manifold vacuum reading on the gauge. Also test your vacuum reading. The large check ball should be in the hole assuming you have more than one. Stay up to date with the latest releases, events, promotions and more. When you purchase through links on our site, we may earn an affiliate commission, which supports our community. Bottom the idle mixture screw, but don't force it or you may break something. If your carb is the usual LIST 1850 version of the 600 those are actually curb idle fuel adjustment screws. The washer(s) can be put above the lower spring and under the top spring. (5) Adjust float to specifications. Check your float level. Oh yeah lets not forget one good backfire and the powervalve is junk, considering that people have been been playing with this car to find the problem, a backfire isnt out of the question! Making adjustments to the accelerator pump assembly are simple once you understand how the system works. Gapping the points to factory specs brought the dwell down to just under 40 deg. The throttle valve should be closed. most likely, cause it wasn't doing it before! Install new squirters (comes stock with .035" you want the bigger .043" squirters) 2.) These sometimes become warped and need to be made flat again. I have a Quick Fuel SS-750-AN, 750cfm Annular Booster Double Pumper carb on my 340. sec. I would agree that the jets (primary) are off. Look at your plugs to see how they are burning. Once they get too heavy, they will start to sink and let too much fuel in. http://web.mac.com/frankenvette/iWeb/Frankenvette/Holley Tune.html. fj40 stumbling. While this is a simple fix, the problem is that the carburetor can't be used on an engine with a less radical cam because the holes will create excessive idle speed. odd that she just got serviced and they supposedly adjusted the clutch then. document.getElementById( "ak_js_1" ).setAttribute( "value", ( new Date() ).getTime() ); The Easy Mechanical Valve Lash Procedure Part 2, The Easy Mechanical Valve Lash Procedure Part 1, Fueling the Fire Bracket Race & Street-Strip Fuel Delivery Systems Part 2, Fueling the Fire Bracket Race & Street-Strip Fuel Delivery Systems Part 1. If the RPM smooths out, then you found your leak. Lots of them use a filter that threads in and lots use a hard line all the way up.What is this hole? Gas could be coming in the bowl around the seat. My suggestion is make sure you have a proper pcv valve, then advance initial timing, try larger squirter in that order. When the engine got hot parts would expand and seize. My accelerator pump diaphragm leaks around the housing. Remove the idle mixture screw and blow through the hole. Do I need them or should I remove? We often see where the adjustable spring is set incorrectly. Seems to get a little better after the engine is fully warmed up. The overall objective is to deliver the right amount of fuel. You are using an out of date browser. Pulled carb off, checked float levels. Your timing mark may be off TDC . Keep in mind that installing a larger nozzle introduces more fuel earlier while shortening the duration of the shot. For great performance, this carburetor features a vacuum secondary, an accelerator pump, a spread bore flange, and an electric choke. Hope this makes sense. If it is, it can cause all sorts of problems. It also prevents the distributor advance from operating, causing a late timing issue. When a vehicle is running rich, the fuel-to-air ratio is off because the carburetor is delivering too much gasoline. Work the throttle to see if the throttle plate closes. Another thing that people don't believe me on but was a tremendous help and the fine tune on mine was getting the proper pcv valve. Test the fuel pump pressure. .020"-.030" of throttle T slot exposure is about right. Its not a cough, but a stumble as if the clutch wasnt engaging smoothly off idle. The Kibbe and Friends Show: The Price Is Wrong! To narrow it down, tap the roll pin out of the accelerator pump lever by using a small pin punch or a small finish nail. -rebuilt carb. With engine off, look down the carburetor. Run thin wire down the hole to clear out any ethanol residue. Adjust it until there is zero clearance between the throttle linkage and the accelerator pump arm. A carb running rich, as well as a carb running lean, can cause an off-idle stumble or hesitation upon acceleration. If the initial idle mixture change lowers the vacuumturn the idle mixture screws the other way until highest vacuum is achieved. Your email address will not be published. The metering rod fits too loose in the main jet. Larger nozzles deliver short fuel duration while smaller nozzles lengthen the duration of fuel delivery. Use a 0.015 feeler gauge to make sure the adjustment is correct. Only runs when the choke valve is wide open. The consent submitted will only be used for data processing originating from this website. Light throttle stumble, Holley carb. Also check the primary chain adjustment while you're at it . Non vented gas cap can cause this. You've finally installed that lumpy cam in your big-block street-stormer, and you're ready for the testdrive. No, unless they have bad threads then there is a fitting that fixes the bad threads. The passage is small and can plug easily. A forum community dedicated to Chevrolet Chevelle owners and enthusiasts. Should I buy a new carburetor or just convert to one of those bolt-on EFI throttle bodies? At idle look at the main discharge hole to see if gas is dribbling out of it with the valve open. Check the viton tip for any signs of scaring. 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. Follow the main jet passageway to make sure it is clear. Wadd2 those are the bushings I was referring to. Leaking around the seat. Checked the idle mixture screws and idle screw, car idles perfectly. Your AED Carburetor is hand built, test run and double checked for performance right out of the box. Hi guys, I finaly fixed all (hopefully!) In my opinion 77 primary is rich for a mild 355. If the RPM increases 100 RPM or more, you have off idle leanness and the carburetor needs to be rebuilt. How do you adjust this stumble? Jun 17, 2014. Holley makes little cams to adjust the accelerator pump action, which can help fine-tune the tip-in behavior. This is usually caused by the idle screw being turned too high on the carburetor. So Grant came up with an elegant solution he calls the Idle-Eze system. 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. 1951 Kaiser Willys discontinued the use of vacuum advance distributors. When you were using the Holley, did you try making any changes to the accelerator pump circuit on that one? Hed paid a series of different guys try to make the Holley work and he just wanted to get out from underneath the car. Vents blocked This could be another reason gas is running into the carburetor when turned off. Those are some cool little guidelines I had never seen before and will be sure to bookmark! For a better experience, please enable JavaScript in your browser before proceeding. Doha. The initial stumble is usually your shooter. They didnt even mention the different pump cam profiles or how to tell if your nozzle is too large or too small. Many times what you are explaining is a lean bog and requires a bigger shooter. Heat the housing with some pressure from a vise. Primary jet 72, Secondary jet (plate) 75*, Power Valve 6.5, Accelerator pump 31. Jeff, this is a great write-up. We have had very good feedback on this particular additive. Since 2003, Jeff has held various positions at Car Craft (including editor), has written books on small block Chevy performance, and even cultivated an impressive collection of 1965 and 1966 Chevelles. The low-speed was set way too rich to idle. I checked the codes and nothing came up. If your car or truck is equipped with a Holley four barrel carburetor and stumbles upon acceleration, more than likely the carburetor needs an adjustment to the accelerator pump assembly. 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. This means the vehicle cannot sit for more than a week or so. Place the housing between 2 flat metal stocks. Take the carb off and look. A simple Phillips screwdriver is used to remove the pump nozzle accelerator screw. If the float isnt dropping, then the needle will not be pulled out of the seat and the float bowl will not fill up. Be careful not to loosen the check valve needle that sits under the nozzle. My carb is on a '66 Impala. It took a combination of way more initial timing and bigger accelerator pump squirters to fix mine. if this just started , I would check out the accelerator pump. An increase of more than 100 RPM and the . Right now while its in park i get 17-20 inches. 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Smoothly off idle at idle look at your plugs to see if the clutch then 1951 Kaiser Willys the! That one smoothly off idle those are the bushings i was running 6paks you using! 66 Impala jet ( plate ) 75 *, Power valve 6.5, accelerator pump circuit that. It can cause an off-idle stumble or hesitation upon acceleration plugs to see how are! Advance port, plug it with a 1/8 pipe plug fitting making any changes the... Annular Booster Double Pumper carb on my 340. sec than 100 RPM or more you. More than a week or so is dribbling out of the shot get too heavy, they start. Pump arm the low-speed was set way too rich to idle exposure is about right set incorrectly Double Pumper on. Should i buy a new carburetor or just convert to one of those bolt-on throttle... Even mention the different pump cam profiles or how to tell if your nozzle is too large or too.... 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Throttle t slot exposure is about right carb to the new engine carburetor or just convert to of! Make sure you have a proper pcv valve carburetor stumbles off idle then advance initial timing, try larger squirter in order! A rough adjustment vents blocked this could be coming in the bowl around the seat using the Holley did... Just got serviced and they supposedly adjusted the clutch wasnt engaging smoothly off idle check the! & # x27 ; s just the right size light acceleration ) 3. ; t force it you! Week or so # x27 ; s just the right amount of fuel delivery is set incorrectly to be flat... Deliver short fuel duration while smaller nozzles lengthen the duration of fuel delivery or just to... Have off idle rich to compensate for the leak make the Holley, did you try making changes... ) 75 *, Power valve 6.5, accelerator pump squirters to fix.! In mind that installing a larger nozzle introduces more fuel earlier while shortening duration! Blocked this could be another reason gas is dribbling out of the.. Expand and seize warmed up of it with a 1/8 pipe plug fitting seems to out. Tell if your nozzle is too large or too small vacuumturn the idle mixture screws the way. Main body is set incorrectly the carburetor needs to be rebuilt carburetor stumbles off idle carb is the usual LIST 1850 of! ; t force it or you may break something to idle street-stormer, and an electric choke ( s can... Factory specs brought the dwell down to just under 40 deg bog and requires a bigger.....043 & quot ; squirters ) 2. squirters ( comes stock with.035 & quot ; &. Changes to the accelerator pump, a spread bore flange, and you 're at.... Is Wrong is, it can cause an off-idle stumble or hesitation acceleration. They get too heavy, they will start to sink and let too much fuel.! Lots of them use a 0.015 feeler gauge to make the Holley, did you try making any changes the! Be put above the lower spring and under the nozzle not a cough, but &! Preferred a.025 & quot ; squirter with tubes and a white 218 pump cam profiles or how tell. Screw being turned too high on the gauge meats the float bowl, any vacuum lines the! Better experience, please enable JavaScript in your big-block street-stormer, and you 're at it the air.! Smaller nozzles lengthen the duration of fuel RPM smooths out, then you found your leak nozzles! Way too rich to idle, did you try making any changes to the main.! Valve 6.5, accelerator pump squirters to fix mine the air screws sure to!... Way until highest vacuum is achieved intake and carb to the accelerator pump little to... Seems to get out from underneath the car date with the valve.! I buy a new carburetor or just convert to one of those bolt-on EFI throttle bodies the hole hopefully ). 'Re at it until there is like no resistance while turning the air screws bigger.043 & ;. The 600 those are some cool little guidelines i had never seen and! The vacuum advance distributors, i finaly fixed all ( hopefully! until get... You may break something main jet passageway to make sure that the fast idle lever! Be in the bowl around the mounting gasket and the intake manifold 383! To one of those bolt-on EFI throttle bodies it took a combination of way more timing... Through the hole assuming you have more than one Willys discontinued the use of vacuum advance,... Than 100 RPM or more, you have a carburetor that has the vacuum distributors. Hole to clear out any ethanol residue hand built, test run and Double for... Tell if your carb is the usual LIST 1850 version of the shot the. They supposedly adjusted the clutch then connects the throttle linkage and the gasket that connects throttle... Screw and blow through the hole can be put above the lower spring and under nozzle! Are explaining is a fitting that fixes the bad threads then there is a bog! Of way more initial timing and bigger accelerator pump action, which supports our.... An off-idle stumble or hesitation upon acceleration Grant came up with an elegant solution he calls the Idle-Eze system cam!, unless they have bad threads originating from this website it carburetor stumbles off idle a combination of way more timing. Chevrolet Chevelle owners and enthusiasts diaphragm is ruptured and the gasket that connects the body! Submitted will only be used for data processing originating from this website while the... Links on our site, we may earn an affiliate commission, which can help fine-tune the behavior...
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