I’m seeking troubleshooting tips to solve an apparent engine surging issue on a ‘66 4-spd coupe. I don’t know the engine history, but I expect it is equivalent to a 350 HP-327, with relatively low miles since being rebuilt. The car has a Holley 1850-12 carburetor installed on an aftermarket aluminum intake with a heat spacer under the carb base. The carburetor is very clean and probably not very old (at least mileage wise). It has an electric throttle solenoid to raise the idle for the A/C compressor. The choke is electric. Overall, the engine runs strong, starts very good hot or cold, good acceleration with no stumbling / hesitation or backfire, smooth steady curb idle, etc. The car idles about 800 rpm w/o A/C, about 1k rpm with A/C on.
The surging (jerking) is most prominent with foot off the gas, letting the car coast in gear. It also occurs at slow speed (in gear) with foot on the gas slightly. In these instances, the car will jerk repeatedly until gas is steadily applied. At cruise speed 30 mph and above the situation is less prominent but slightly noticeable. This happens whether the engine is hot or cold. The choke, A/C solenoid, and throttle mechanism all seem to be operating correctly as best I can tell. The situation is annoying, but the car is drivable. I would appreciate thoughts on the cause and possible remedies. Thanks in advance for taking time to respond.
The surging (jerking) is most prominent with foot off the gas, letting the car coast in gear. It also occurs at slow speed (in gear) with foot on the gas slightly. In these instances, the car will jerk repeatedly until gas is steadily applied. At cruise speed 30 mph and above the situation is less prominent but slightly noticeable. This happens whether the engine is hot or cold. The choke, A/C solenoid, and throttle mechanism all seem to be operating correctly as best I can tell. The situation is annoying, but the car is drivable. I would appreciate thoughts on the cause and possible remedies. Thanks in advance for taking time to respond.
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