1970 chevy c10 cranks and runs but when you step on gas, it sputters
The accelerator pump may not be working properly.
It should be given a through tune up. It may be a bad coil, carburetor needs work, or a plugged fuel filter? Its it is a carbonated engine, your float may be bad and your flooding the engine with too much fuel. Have you checked the timing? The distributor may need attention also. Distributor springs may be broken or weak, and the points may be bad or need cleaning or adjusting. Or a major tune- up.
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