Please forgive me if I post this in the wrong location, I am new here and this is my first post. I have a 1960 Bel Air with the original 235. I recently rebuilt the single barrel Rochester b due to the float Bowl gasket leaking. During the rebuild I replaced everything brand new internally including the accelerator pump. Now that I have put it back on the car it idles fine and if you slowly accelerate, it will accelerate fine. The problem is when you step on the gas like you were taking off from a stop light the car wants to die. When it does this you can hear the carburetor sucking an excessive amount of air and if you do not let off the accelerator the engine will die. The vacuum advance is working. I have been struggling with this for a couple weeks now and I am not sure if it is something I did wrong while rebuilding the carburetor or if the timing may be off. After I installed the carburetor I noticed the vacuum advance was not working so I checked the gasket between the carburetor and the intake manifold and noticed there was not a slot in the gasket for the vacuum port that leads to the vacuum advance. I remove the gasket, cut a small slit in the gasket to supply vacuum to the advance and it works now. Any advice or helpful tips would be greatly appreciated. Thanks in advance.
Engine off, looking down carb, choke open, do you see it squirt had when opening throttle? (Accelerator pump working)? Then at idle, try carb spray around carb checking for vacuum leaks (it will rev up). WD-40 works also & safer. Many years ago my wife's 55 with 235 was doing that once. Mice had built a nest in air cleaner housing. Easy test...air cleaner off it ran fine. Another time I rebuilt carb, accelerator pump circuit not working properly. Carb off car I used water testing. Turned out the check ball in kit was too light weight. When corrected I air blew everything out, accelerator pump was leather so I oiled leather. Back on car it worked great. It has to squirt quite a bit of gas to prevent stumble, like about a teaspoonful. Sent from my SM-S320VL using Tapatalk
First step is to do as Sevenhills1952 suggested and take the air cleaner off and while looking down the throat of the carb work the throttle to see it you get the squirt of fuel out of the accelerator pump discharge nozzle. If there were more than one gasket for the same spot in the kit did you match the new gasket to the old gasket you took off? Some of the kit manufactures now make kits that fit several modes of the same basic design carb and they include several choices for gaskets in spots and the wrong gasket blocks a passageway for one of the circuits. Looking at this link there are several different throttle body to bowl gaskets and even more bowl to top gaskets. https://www.carburetor-parts.com/B-BC-BV-Gaskets_c_597.html Other things that might cause it. Float level too low and it runs out of gas in the bowl on acceleration but will idle. Restriction in the fuel supply line that lets a little bit of fuel flow but the bowl runs dry on hard acceleration about the time you go to shift. I don't think that applies here though. Part missing, like a check ball or the wrong piece such as a too big or too small check ball. Accelerator pump linkage not hooked up or hooked up wrong.
Years ago I had a 1957, 235 Chevy truck....SAME, EXACT thing happened to me. It took me about an hour to figure out that a piece of flaky rust was laying in the fuel line and every time I tried to accelerate quickly, the flake of rust would pop up and push against the fuel line causing it to block and stall out. At idle, the rust would lay down and fuel would flow. Blow the line out from the carburetor towards the rear and you might just fix the problem.
I don't think new made rebuild kits are as good as they were 30-40 years ago.Losts of accelerator pumps aren't leather any longer.I would check e bay/swap meets for old unused kits to get better parts.
With the air cleaner removed and looking down the throat of the carburetor you can see gas squirt out but it does not look like it's a teaspoonful. Yes when I removed the old gaskets then I matched them to the new gaskets in the kit to make sure I got the correct ones and if I remember correctly the float is set to 1 3/4 drop and shuts off at 1 9/32. The only other thing is that I may have put one of the balls in wrong since there is a small aluminum and a small steel ball in the kit. I replaced the pump with one that has a rubber cup on it where as the old one had a leather cup. I had to measure the old pump to make sure I ordered the correct one since they make 2 different ones with the round stem. I may pull the carb and open it up again to make sure everything looks and working correct. Thanks for the tips.
So first of all I want to say thank you to everybody that made a suggestion. What I ended up doing was removing the carb, and replacing the accelerator pump and spring with the old one and it seemed to take care of the issue. What I noticed was that the new accelerator pump would not go down all the way even with the old spring in it. Like it was getting hung up on something inside. When I removed the new pub with the rubber cup it had actually started to pull the cup off the stem. Just want to say thank you again for all the suggestions.
If you're talking about the idle mixture screws, they will have very little to no effect on fuel mixture at any speed much above idle. The idle circuit, by design, will not effectively alter the fuel mixture of the main circuit, the power circuit, the choke circuit or the accelerator pump circuit.
No, I was referring to the air fuel mixture screw. Not the idle screw. It seems he's found his culprit now anyway.
OK. Well I may have confused things a bit by saying idle mixture screws instead of "screw" (singular) since it's on a one barrel carb. This interweb thing is handy and all but sometimes it would simpler and clearer if we were both looking at this carb in the same room at the same time and could point to which screws we were talking about. But if it's fixed, it's fixed. Unless it isn't.
All rebuilding kits are not created equal. There are still excellent kits with leather accelerator pumps available; but they cost more money. Jon.
I tried to save money when I bought my kit, which was a mistake. It was a "standard" kit for these carbs which came with gaskets, springs, check balls and the pump which has a rubber cup and a flat stem on top. My carb has the round stem and leather cup so I had to order the correct pump separately which cost more money and turned out to be an issue and I also had to order the air idle mixture screw and spring since it didn't come in the kit either. Now I wish I wouldn't have been such a tight wad and just bought the more expensive one to begin with. Probably would have saved myself a lot of headaches from the beginning.
I am building a 1957 chevy truck. I didn’t have a motor or transmission when I got the truck. Do you know if the 1960 rochester will fit my 57 235. What’s the difference between the 1957 and the early 1960 1 barrels without the vacuum advance?
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