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My '53 Chev 3/4 has run a little rough since my restoration was completed and I'm starting to wonder if I have the right carb. Here's the situation. The truck had a '55 235 in it when I bought it. The carb was a Carter YF-2101S which according to the manual is correct for 55-56. I replaced the '55 235 with a '61 235 out of a '61 Chev Biscayne. That engine didn't come with a carb and I went ahead and used the Carter YF-2101S. It starts and it runs, but is sluggish and I have to keep the throttle pulled out about half-way to keep it running. Driving it is not cool because it wants to stall constantly. In checking a few sources, I'm seeing that a '61 235 had a Rochester BC carb. Both the Rochester and the Carter are downdraft carbs. I also found 2 different carb model numbers and no indication as to which one would be appropriate for the Biscayne motor. A '61 Motors manual lists a model BC-7013003 and also a BC-7019000 for '61 vehicles without specifying which one would go with a Biscayne of that model year. Then a later Motors Truck manual lists a Rochester 'B' (not 'BC') for 60-62 with a model number of 7015011. I'm guessing that one of the two BC model carbs would be appropriate for a Biscayne CAR motor of that year, but that's as far as I can get. Does anyone have a parts manual or something that would give additional information as to which is appropriate? Would it matter which model I use for that year? And last, would this likely lead to the problem I described in the first place? Any help would be appreciated. Thanks.

Rick- I can't tellyou what carb was intended for your 61 engine, but if your carter will bolt on it will work. It sounds as though you have a vacuum leak. Check at the base of the carb and at the intake manifold where it meets the head. It could be many other things as well, but get the tune baselined to stock specs for your engine year, set the timing and idle speed correctly, adjust the idle mixture on the carb and see how it runs. I've spent too much money over the years trying to fix stuff like this without truly knowing where I was to start with.

Devin

Rick,

First, I agree with Devin about the possibility of a vacuum leak and/or a gasket problem (the gasket at the base of the carburetor needs to be there and needs to be orientated correctly to a hole in the base of the carb).

It is odd that Rockauto.com does not show a carburetor for a 1961 235 Biscayne but shows a one-barrel Rochester for a 1961 235 Bel Air. Nonetheless, the 1-barrel Rochester should work satisfactorily on any 235 that it can be bolted onto (as long as it is equipped with a properly working manual or automatic choke mechanism).

Tim

Also check for a worn throttle shaft. If the idle mixture screw does not produce changes in RPM when turned both in and out, you have a vacuum leak. With the engine running, try and move the thottle shaft, wiggle it it up and down and listen for a variation in RPM and look for gas seeping out along the shaft and running down the base. I have this problem with a couple YFs I am dealing with right now. I have one with a machinist who is attempting to make me some new bushings and polish the shaft.

Your truck has/should have a manual choke. Passenger car carburetors had automatic chokes after 1949, so if you have a passenger car carburetor without a manual choke conversion, you will have trouble with cold starts, and maybe low speed operation. Your late-model passenger car carburetor has an automatic choke that won't work without the stove on the exhaust manifold and the heat pipe to the choke housing on the carburetor. Does the stalling problem improve or disappear when the engine gets to normal operating temperature? If so, you have a carburetor heat matter to resolve- maybe the heat riser valve is not working properly. If the problem persists or worsens as the engine gets warm, the carburetor may be getting too hot- heat insulator under the carburetor is missing. Memory is foggy on that matter, but most 6-cylinder engines used an insulator of some sort. As mentioned by others, the base gasket may be blocking a vacuum passage, and causing the power circuit to be continuously fully open. That condition will give you poor idle and low-speed operation, which can be concealed by pulling the throttle a small amount as you indicate you are doing.

Harvester