'64 C60 w/ 292/420/2 speed and original Rochester.
When I first rebuilt the truck I drove it how I always drive the larger trucks and would use engine load to assist in slowing down, rarely applying the brakes until <10mph. At the time I was on regular 292 Delco plugs and a points dizzy. Everything worked beautifully. After a year I upgraded to an OEM HEI unit that I sourced off a 250(?). Put heavier advance springs in, rewired the ignition, matched with HEI wires, and installed larger gapped plugs (Autolite 3923 copper gapped at .044). Truck still runs like a dream and pulls strong under load.
I cannot however, utilize engine load for braking anymore. Doing so causes engine popping/miss, almost like backfire but not exactly. Typically symptoms of over fueling as the same things happen if accelerating with the choke partially on. I've torn down the carb numerous times, checked float levels etc, and all is within spec. Pulling and inspecting plugs seems to indicate good combustion. If she's running rich the plugs aren't indicating. Cold starts (sub 32F) require heavy choke but once warmed up she idles great with no choke and doesn't idle rich based on both smell and exhaust color. For the last two years i've scratched my head on this and cant seem to diagnose it. Again, under any throttle the engine purrs like a kitten, but as throttle is released while in gear and rpm start to fall, it occurs.
Am I missing something small? Does the carb need tuned differently than standard? Maybe its with the plug gap or advance springs? Im at a loss and appreciate any input. For now I just drive and use the brakes, but id like to get back to engine braking to save on pad and drum wear since brake parts are hard to come by.
Last edited by HFfarms; 02/13/2024 7:00 PM.
