Reproduction Parts for 1916-1964 Chevrolet Passenger Cars & 1918-1987 Chevrolet & GMC Trucks


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Joined: Jan 2023
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axel Offline OP
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i replaced my carb
i have a number 57 main jet
runs very rich
car runs good but does not run smooth
tail pipe very sooty

How do I adjust?

Last edited by Peter_Gariepy; 01/19/23 04:56 PM.
Filling Station - Chevrolet & GMC Reproduction Parts


Filling Station


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I assume that the automatic choke is opening completely and that the float level is correct. Those would be the first 2 items to check. I also assume that you did replace it with a correct year Rochester carburetor.

I would also check for vacuum leaks as well as make sure the idle mixture screw is set correctly. I know that idle mixture does not have much if any affect on operation at speed but if the idle mixture is rich it will produce soot.

I do not know what size the main jet should be. Hopefully one of the experts will respond.


Rusty

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Typical problem when the vacuum power piston is either stuck, its spring is missimg or not recieving vacuum due to port between carb. base and intake manifold restricted by gasket or improper insulator under cabuetor.
To make a long story short power piston is stuck in the rich position.
First thing I would do is remove the carb. and see if the litle hole on the bottom of the card. base is covered up.
The correct insulator block under the carb. has four notches, one of them must line up with the hole under the base. f you have a gasket in this area remove it, it is NOT necessary.

Last edited by Chev Nut; 01/19/23 07:57 PM.

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axel Offline OP
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you are a genius!when replacing carb i did plug the port.repaired and runing great.thanks that carb is rtelativily simple but wish i could find technicial explanation. thanks again axel

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axel Offline OP
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i got a reply from chev nut.followed his advise and found and repaired prob.i had plugged port with gasket...tks axel

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axel Offline OP
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chnverted my chev to 12 volts.what is the resistor size to use for the fuel gage tks axel

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axel Offline OP
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thanks for reply.chev nut led me to a fix.i had blocked a port pn carb base while installing...fix and doin great tks axel

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Do a Google search for 6 volt fuel gauge resistor. There are lots of sources. They are sometimes called a “Runtz” resistor.

You also might want to start a new thread when you change the subject. Otherwise people might not realize that you ask a different question.


Rusty

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