VCCA Home Forums TECHNICAL - 1945 AND NEWER 1949-1954 carb jet size

what is the correct carb jet size for a 1959 chev 235 carb? Thanks

Ross, I have one of those carbs in my shop and will check it out this afternoon, is the carb for a passanver car, or pickup truck?

Ross the carb (Rochester BC), passanger I checked has a 58 main jet, I also have several Rochester model B carbs for trucks with manual choke, I always replace the BC with a B on my vehicles, I just don't like the Rochester automatic choke. On the last tour someone asked me what that extra vent knob was for, it is the choke. I only use it for cold starts, half choke unless it is really cold and reduce it to no choke after the engine warms up ,3 to 5 minutes. I believe the automatic choke was added so that the lady drivers would not pull the knob out to hang their handbag on!( after the auto choke was introduced they went to pulling the hand-brake out for a handbag hanger Ouch!, I remember one old maid school teacher back in 1954 that complained to the Service manager that her Belair 4 door had lost power and the hand brake was pulled out several clicks!

My parts book only goes up to 1954 and it also shows a 58 is standard, a 57 one step lean and a 59 is one step rich the part numbers are 7002958 (standard) 7002957 (one step lean) and 7002959(one step rich) FYI The 261 engine has a slightly different carb (larger venturi etc.) and it runs a 7002965 (Standard) a 7002964 (one step lean) and a 7002966 (one step rich) Note: the last two digits of the part number are stamped on the face of the jet. I check them with a number drill bit and then mike the drill rod to verify that the jet has not been drilled out, which some shadetrees did to richen the mixture.
Generally in a passenger car the mean altitude at the home location was the guideing factor in which jet was best.

The 1959 standard transmission cars had a #57 jet and the P.G.s had a #53.The small trucks had a #56.The Power Glides were leaned down and recalibrated for economy in '59 and did give good milage.Most 235 carbs ran a #56-#58 jet size.

I remember in 1958 gasolene was what everyone now considers "Cheap" Gas was about 30 cents per gallon and 20 mpg was considered good, the minimum wage was $1.25 per hour. now Gas is $1.40 a gallon and the minimum wage almost $6 per hour. and good milage is around 25 mpg for a full size auto, so how about that "cheap" gas?

THANKS EVERYONE FOR YOUR HELP. I PUT A 59 MOTOR IN MY 50 BEL-AIR BUT IT ALWAYS SEEMS TO RUN RICH SO WILL HAVE TO CHECK JET SIZE WHEN I REBUILD CARB THIS WEEK. ROSS

Ross, Check to be sure that the vacuum power piston is moving.I have seen several lately that were froze in the rich position.Also be sure that you have the correct insulator under the carb..The "notch" in the insulator MUST line-up with the vaccum hole in the bottom of the carb..If it dosen't the power piston will be in the full rich postion all the time.

Also check that the choke pulloff is operating fully and be sure the choke isn't closeing after the engine is warmed up. The instructions for the rebuild kit and the shop manual tells how to set the choke operating apparatus. yes the "power piston" can stick in the rich position on the Rochester carbs, for several reasons.