My choke and high idle on my 81/300/carter 1bl work fine, but the high idle is too high for comfort. I don't have the factoy tach, or a hand-held one, but i'd estimate its about 1800rpm. The problem is when I try to adjust it down the engine doesn't start smoothly. It will sputter, and then roar to life. I have been tweaking this forever, and it seems like every adjustment has an unwanted side-effect. I really don't want to mess with the choke anymore, because its working and not hindering normal driving anymore. Can someone give me some advise on this, or maybe a pic of their's on the high idle step? I had the high idle perfect at one time, but the choke was wrong with that adjustment, and it made the engine bog under aceleration.

Few notes:
Choke heater is connected and operational
Intake snorkel duct door working
electric assist choke connected and working
Truck runs, drives acelerates, idles fine otherwise

 

Look on your carb for the fast idle cam. It will look like a large plate with steps on it. There should be a screw that you can adjust that hits the steps on the cam.

 

there are 2 idle screws a fast idle and a normal idle, the normal idle is closest to you (if standing at the grille) the fast idle hits the stepped cam as stated.

 

My mistake for not clarifying, I know which screw is the high idle and everything, its just the adjustment thats giving me the problem. I am unsure of which "step" the screw should be contacting. I set it to what I think is the top step. The "lobe" has three steps on it (unless the top of the lobe itself counts). Does the thing automaticaly move down the steps as the truck warms up? The problem is the idle is too high, and when I lower it, it hesitates pretty bad before starting. It starts low and sounds like its gonna die, and then roars to life.

 

Yes it does but you have to blip the throttle to allow it to move to the next step or all the way off the cam when the choke is fully opened.

 

Yes, the choke determines where the cam is and what step the screw is on. So on a cold day, with the choke fully closed, it will be on the highest step, giving you the fastest idle. As it's warming up, if you "kick" the gas pedal, the screw will come off the cam, and that will let the cam fall to the next step IF the choke is starting to open. You usually have to kick the throttle, since the choke mechanism is usually not strong enough to slide the screw over the cam. So if you start the truck and then go back in the house, after a few minutes, yes the engine will be screaming unless you go outside and kick the pedal to knock it down.

The choke system is very difficult to get correctly adjusted. You have to turn the large black round plastic piece to set how much the choke activates, you need to make sure the choke pull-off is working correctly, all the lines to the choke housing and the exhaust manifold are hooked up(if your truck has them), and after that, the fast idle adjustment. It will probably take a few cold mornings to get it close to being right.

 

Thanks Franklin,

Thats the issue I have, I adjust it and try it out in the morning, and have to live with any side-effects until the next day. I guess i'll have to adjust the choke a bit to match the lower high idle rpm. So when you engage the choke in the morning with the truck cold, it starts on the high cam step, and then you can give it a small pedal push to move down a step without canceling the choke completely?

 

Yes, but it all depends on how you have the round black piece adjusted. You can have it adjusted more to the "richer" direction(I believe that is written on the black piece) and it will have more pressure to close the choke and keep it closed. So it would have to warm up more before you could kick it down.

If you have the round black piece adjust more to the "leaner" direction, and the choke just barely closes on the cold morning, then when you kick it down, it might even go to the second step on the cam, the choke door may open too much, and it may stall.

You need to also make sure the "choke qualifier" or "choke pull-off" is working. That is a piece that works off engine vacuum, and depending on the carb, it has a arm that goes to a vacuum diaphragm and then to the choke linkage. When you hit the throttle once before you start it on a cold morning, the choke is going to slam shut. This is ok to get it started, but is too much for it to run and it will "choke out" the engine. The choke pull off builds vacuum from the engine, and as it does it cracks the choke door open just a little bit so it will keep running. There is a spec for this crack, and you bend the linkage to set it.

 

Hmmm, I think mine is just the thermal-electric choke that opens itself as the hot air from the heater tube passes through it. I think I have my choke adjusted more to the rich side (towards the driverside). I may need to lean it out a bit in order to get it to high idle on a lower setting.