Where is the fuel filter located on a 1980 Chevy 305?

More than likely mounted near or in the carburetor. Some screw directly into the carb, follow the fuel line. It is a very large bolt. Use a line wrench in order to not round it off. Watch for a fuel spray when you loosen it, and pay attention to how it and the spring go in. Buy the filter and you will have an idea what your are looking for.

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i just replaced the filter on my truck

make sure the plastic washer is in good shape otherwise the filter chamber will go too far in to the carb bending the filter.

make sure the hole is in the front of the filter.