yeahbuddy

I have a 68 Cutlass Supreme with a 350 small block and a 4 barrel QJet. It overall runs well with a couple issues. There is a drain-back issue so if it sits overnight I need to pump it 2-3 times prior to starting. Here is my issue. Once I prime the carb and start it up, it starts on a very high idle. About a month ago, if tapped on the pedal once it goes from high to mid-range idle and tapped it would turn into a low idle. Lately, it fires up at a high rpm idle and regardless of how many times I tap or press the pedal it does not change. If in park it will continue to stay revving high until I drive for a few minutes it eventually idles properly when I come to a stop. This morning, it did the same issue so I turned the car off once it got to around 190degrees to take a closer look at the carb. Once I turned it off the engined knocked/fired for a couple seconds after shut down then shot out some white/blue smoke from the carb and choke. I thought I caused some serious damage but it started up again. Do these issues sound like it is choke related? The car also has a hard time hot starting after sitting for 15-20min from shut down. Any help would be great. Thanks.

BlackGold

First, if the carb is draining (or all the fuel is evaporating) between starts, pumping the pedal multiple times does no good. Pump it once to set the choke, then simply crank the engine until the fuel pump has a chance to fill the bowl. I bet it'll start just as quick this way as what you've been doing. Also, if the fuel is draining from the carb, this can be fixed.

As for why it won't kick down from a fast to slow idle, there's two possibilities. First, the choke linkages might be dirty or corroded. Believe it or not, the kick down simply relies on gravity to pull the fast idle cam to the next lower step. Clean everything with carb cleaner spray and inspect for corrosion. Work it by hand (when warm, so choke is not set) to see if everything moves freely. Don't lubricate anything, as that will only attract dirt.

The other possibility is that the choke thermostat coil is either adjusted too tight or has simply lost its spring and won't unwind itself once warmed up. Start by adjusting it more lean. That will probably fix the "stuck on fast" problem, but if it now doesn't choke enough when cold, you know you need a new thermostat coil. I'm not sure what that means for you '68 people with a divorced choke.