general - carb. maintenance

[Matt F.]

Is there anything I should be doing as far as cleaning, etc., for an installed carburetor that gets fairly regular use? What's the normal service life for an AFB type carb?

thanks,
Matt

[Duke W.]

Re: general - carb. maintenance

The AFB is probababy the simplest, most reliable and trouble free four-barrel carburetor on the planet, but it does have some faults. The Quadrajet is not far behind, and is only "worse" because it was an emission era carb that has more bells and whistles, but it has a less finnicky choke system. The WCFB is also a good design. All these share an architecture that has no "wet" gaskets - the fuel bowls are contained completely within the main body casting unlike Holleys whose fuel bowls are sealed below the fuel level by gaskets, which are a major leak source.

Assuming your AFB has a hot air choke system, this system tends to get dirty causing the choke vacuum break piston to get sticky, so if choke operation degrades cleaning the choke mechanism is called for.

The choke housing can be removed from the carburetor on the engine, disassembled, and cleaned.

When reinstalling, make sure you install a new small O-ring that seals the vacuum passage.

Also, be sure you change the fuel filter at reasonable intervals. Same with the air filter and make sure the filter seals to the housing and the housing to the air horn, so as not to allow unfiltered air to leak in. If the carb tends to get a dirt film buildup on the choke valve and venturis, it's drawing dirty air.

The throttle shaft bores wear with use and will eventually cause idle speed issues, but this is common to all carbs.

They can be rebuilt and overhauled virtually indefinitely. Renewing throttle shaft bushings is expensive, but worth it if you have a correct model/date code carb for your engine.

Duke

[Duke W.]

Re: general - carb. maintenance

The AFB is probababy the simplest, most reliable and trouble free four-barrel carburetor on the planet, but it does have some faults. The Quadrajet is not far behind, and is only "worse" because it was an emission era carb that has more bells and whistles, but it has a less finnicky choke system. The WCFB is also a good design. All these share an architecture that has no "wet" gaskets - the fuel bowls are contained completely within the main body casting unlike Holleys whose fuel bowls are sealed below the fuel level by gaskets, which are a major leak source.

Assuming your AFB has a hot air choke system, this system tends to get dirty causing the choke vacuum break piston to get sticky, so if choke operation degrades cleaning the choke mechanism is called for.

The choke housing can be removed from the carburetor on the engine, disassembled, and cleaned.

When reinstalling, make sure you install a new small O-ring that seals the vacuum passage.

Also, be sure you change the fuel filter at reasonable intervals. Same with the air filter and make sure the filter seals to the housing and the housing to the air horn, so as not to allow unfiltered air to leak in. If the carb tends to get a dirt film buildup on the choke valve and venturis, it's drawing dirty air.

The throttle shaft bores wear with use and will eventually cause idle speed issues, but this is common to all carbs.

They can be rebuilt and overhauled virtually indefinitely. Renewing throttle shaft bushings is expensive, but worth it if you have a correct model/date code carb for your engine.

Duke

[Clem Z.]

Re: general - carb. maintenance

i have found that most all rebuild kits for AFB carbs have a needle seat to carb top gaskets that have too large a inside diameter and leak thru under pressure with the engine is shut off causing flooding. if the gaskets do not require being "threaded" onto the needle seat they will leak. JMHO

[Clem Z.]

Re: general - carb. maintenance

i have found that most all rebuild kits for AFB carbs have a needle seat to carb top gaskets that have too large a inside diameter and leak thru under pressure with the engine is shut off causing flooding. if the gaskets do not require being "threaded" onto the needle seat they will leak. JMHO

[Matt F.]

Re: general - carb. maintenance

Thanks to you both for the information, I'll put it in my garage file.

-Matt

[Matt F.]

Re: general - carb. maintenance

Thanks to you both for the information, I'll put it in my garage file.

-Matt