I have a 750 cfm 4160 with vacuum secondaries on the stock 283 in my T bucket. The car always immediately stalls if I try to accelerate from a standing start. I realize that 750 is too big for a 283, but I figured since it's a vacuum secondary carb I might be able to get it to work ok. I thought I'd fool with the accelerator pump nozzle to get rid of the stall, but I'm not sure which direction to go, leaner or richer. From what I've read and heard, if the car stalls off idle, you should go richer, but I don't know if the fact that the carb is oversize is something that I should take into consideration. The current nozzle is a 31. Any ideas?
Its lack of fuel causing the bog, some of the 4160's do that. Its my experience if you have one that bogs you won't get it out, I believe it is a manufacturing defect where the throttle shaft is out of phase with the throttle plate so the ****erflies open before the squirter and transition slot is overly exposed.
Here's a read http://garage.grumpysperformance.com/index.php?threads/holley-accelerator-pumps-cams.1790/
Stick you mug up there and look at the squirt I'd say it's the pump cam or an old pump diaphragm, Or just needs a good cleaning. Tell us what you found I've never seen a 4160 or any other Holley I wasn't able to get to run as perfect as a carb can work. My favorite tuning tool for carbs is a wide band O2 sensor..
Properly adjusted pump lever, proper cam and nozzle size... No hesitation. Of course ignition timing and advance curve can make a big difference too. Try putting a little timing in it to see if that helps. Does it just lay down and die or does it pop back thru the carb also? There are a lot of variables. My advise would be to find someone in your area that can check it out and get the right tune on it. I will say this....you and the motor would be a lot happier with something closer to 600 cfm on it. Sent from my Moto G Play using The H.A.M.B. mobile app
Had a stock 283 many years ago, bought a NEW model 1850 (600 cfm) Holley mounted it to the original cast iron intake with an adapter, ran great after a simple float adjustment.
Put one of the Summit brand former Holley carbs on a small block . Worked great right out of the box. Does your carb die if you just baby it from a dead stop or just if you stomp it. Stronger spring to delay the secondaries adjust the pump arm, check the powervalve if it backfires. Check dist for advance.
Bog or hesitate? two different problems. Bog is too much fuel, hesitation is too much air. A cam (longer ramp)and nozzle (bigger), power valve (earlier opening)change may be needed to compensate for too much air. A bog may be related to the power valve opening too soon. Work with what you have. I made two 4100 Autolite 1.12 carbs work on a 272...... ^ 90% of carb problems are ignition related......
I have run a lot of 283's with the old 3310 , 780 cfm holley. It's not too much carb if jetted correctly. I usually ran #29 acc pump nozzle. It doesn't take a big nozzle on the street for this weight of car. Pull the aircleaner and look down the primaries of the carb with the engine off. Now open the throttle arm slowly, you better see a shot of fuel immediately start when you start moving that arm. If you don't, you need to possibly adjust the pump arm adjustment screw , I THINK, without looking you should have at least .020 clearance when the throttle is completely open between the adjustment screw and the pump arm before the pump arm bottoms out the pump itself. If all is well, you may have to change the pump cam or it's position. Just make SURE you have fuel immediately coming out the nozzle when you move that throttle arm or you will have a stumble. Hope this helps. Lippy
It'll help if you understand that there are 2 circuits designed to prevent the hesitation or stumble. Everybody has mentioned the 2nd circuit, the 'accelerator pump' circuit. There is another circuit that comes in quicker than the accelerator pump and it is called the 'transition' circuit. That circuit shares the same fuel source as the idle circuit and it's discharge is a slot just above the throttle blade. When the throttle is properly adjusted the throttle blade will have a slight angle and the transition slot will be exposed and should appear as a 'squareish' looking hole, as the throttle blade sweeps upward when open more of the transition slot is exposed. Fuel is coming thru that transition slot, turn the carb upside down and you'll see a clean spot where fuel washes that area. The vacuum beneath the throttle blades is what is acting on the transition circuit, when the throttle blade sweeps open the fuel is introduced in milliseconds while the accelerator pump is just beginning to act. The sequence is that the throttle blade opens and fuel is introduced thru transition circuit only in that very brief time the throttleblade is p***ing the transition slot and then the accelerator pump shot comes in on top of the transition circuit fuel. All of this happens very quickly, it happens as quick as it takes for the throttle blades to open. The cause of the traditional stumble as you describe is that the throttle blades are open too far at idle so thta the transition slot is overly exposed. Turn the carb over, is the transition slot a 'squareish' opening or can you see that it is a slot. If it appears as a slot then it'll stumble as sure as the siun rises in the East. The only cure is to close down the throttleblade. A doublepumper you can open the secondaries a little in order to close primaries - can't do that with vacuum secondaries. Some holley carbs have .080 holes drilled in the throttle blades. Other carbs have notches milled into the throttle blades right at the transfer slot. Some carbs have an adjustable bolt you can screw in or out to let air past the throttle blades, Holley even has a carb that has an adjuster beneath the air cleaner stud. All of these are controlled vacuum leaks that let air into the engine so the primary throttleblade can close down and pinch off the air to the transition slot. It'd be better if we could see a picture of what your throttleblades look like, if they are open too far and you have mild cam etc then the first thing is to figure out why the blades are open so far. Adding controlled vacuum leaks would be 'Plan B'. Sorry about being lengthy, I'm not very good with words.
Here's an excellent video that explains what "oj" said above. It's easy to change out that screw for one that permits adjusting with the carb on the car.
Thanks for everyone's help, lots of smart people here. I've half decided to just get a Quick Fuel 450 cfm. I figure by the time I've bought the doo dads to get the carb running right, nozzle, jets, power valve, secondary spring, etcetera, I'll have spent a decent chunk of money, and I'll still have a carb that isn't really intended for an engine as small as a 283. I'll see how much of a spending mood I'm in. Btw, I forgot to mention that the car only stalls when I hammer the throttle. During normal driving it's fine. When I do stomp on the gas pedal, the car instantly dies. It does it very cleanly, no bogging or gasping or hesitating or back firing. It's like I turned off the ignition key, stomp on it and bam, the car isn't running any more. Starts right back up, though.
If you go out there and slam the throttle open, watch the fuel coming out of the nozzle. Pay attention... You will see that the fuel continues to spray after the throttle is open. Why? You are trying to compress a liquid. Watch the pump lever... It has a spring on it. When you slam the throttle open, that spring compresses because the gas won't ... Liquids don't compress.. The spring continues putting pressure on the pump arm which in turn keeps squirting fuel into the motor until the lever and spring reach their max travel. That said... Replacing the nozzle does not allow more or less fuel to be squirted. Pump still only holds a specific volume. A larger nozzle allows the fuel to exit the pump circuit faster, a smaller one, slower allowing for a longer stream of fuel. Changing the cam will change the timing of the pump shot... For part throttle driving. If you are not having a part throttle stumble, don't mess with it. When you stop on the throttle, it is open! Cam can be a slow or fast ramp but it will still be at max no matter which one is on it. Try putting a smaller nozzle on it.. Go several steps smaller. See what it does. If it still doesn't, but also backfires it isn't getting fuel at a fast enough rate. Then go bigger by several steps larger than the first one. If it stumbles but doesn't die, you are heading in the right direction. One more thing to watch.... Are the secondaries opening when you slam the throttle open while it is running? One way to tell is to remove the rod from the lever on the right side of the carb... The one coming straight down out of the vacuum chamber. Go out and stomp on it. If it picks up and runs without dieing, put a stiffer spring in it. Sent from my Moto G Play using The H.A.M.B. mobile app
You will like the quick fuel carb. I have used various quick fuel carbs on different cars and was very pleased with the results.
I thought this was a repair and troubleshooting thread , if I would have known it was a replace it thread I could have saved myself a lot of time, I could have just said......replace it.
Plain and simple, that carb is too big for a stock 283. You can probably mess around and get it to work or you can put the right size carb on and be done with it. With a large bore primary on a small engine, you don't get a crisp signal through the venturi or transfer slot.
Interesting, I got same problem with my stock 283 and 600 Holley on a cast iron 327 intake! I'll try all these advices! Sent from my iPhone using H.A.M.B.
It came off a 383 chevy the owner thought it was the problem,it wasn't it was the dist,I put it on my el camino with and adapter and didn't change a thing
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