loping idle on choke

[naa10104]

Hello,

Have a 351 C with 2V 2100 carb. Carb is recently rebuilt and in good order, believe a minor adjustment is needed. Here is the issue ... 25 -30 degrees out. pushed gas to floor let it up slowly twice ... car started immediately but loped or surged ... not a smooth fast idle ... did idle fast but loped. Kept running never stalled after a few minutes I tapped the gas to release the fast idle .. it did so and idled perfectly at normal curb idle speed. What would the most probable cause be for this and what do I need to adjust ? Thanks very much.

 

[Galucha]

Hello,

Have a 351 C with 2V 2100 carb. Carb is recently rebuilt and in good order, believe a minor adjustment is needed. Here is the issue ... 25 -30 degrees out. pushed gas to floor let it up slowly twice ... car started immediately but loped or surged ... not a smooth fast idle ... did idle fast but loped. Kept running never stalled after a few minutes I tapped the gas to release the fast idle .. it did so and idled perfectly at normal curb idle speed. What would the most probable cause be for this and what do I need to adjust ? Thanks very much.

There's supposed to be a small gap between the choke butterfly and the airhorn when cold starting. If the gap isn't the right width it can cause some rough idling before the engine has warmed up.

Here's the adjustment diagram, and the gap is probably gonna be 1/8". Unfortunately I don't have the chart saying what exactly it should be at, in my experience it works to experiment a little and find out what gives the smoothest idle.

 

[barnett468]

there should be no gap between the butterfly and carb body when it is 20 to 30 degrees outside . . the choke at that temperature should be adjusted until the butterfly just closes .

it takes a bit of messing with the butterfly and high speed idle screw to get it dialed in, HOWEVER, any carbureted engine that starts and stays running with just one push on the gas pedal in 20 to 30 degree temps is a winner.

remove the air cleaner and leave the hood up and start the engine.

look at the choke immediately after it starts . . it should be around 3/8" open

open and close the butterfly to see if the engine smooths out . . if it does, simply adjust the choke in that direction.

it is also possible that your vacuum advance is advancing the timing too much so try unplugging the vacuum hose that goes to it also while it is running ad see if that helps.

 

[naa10104]

there should be no gap between the butterfly and carb body when it is 20 to 30 degrees outside . . the choke at that temperature should be adjusted until the butterfly just closes .

it takes a bit of messing with the butterfly and high speed idle screw to get it dialed in, HOWEVER, any carbureted engine that starts and stays running with just one push on the gas pedal in 20 to 30 degree temps is a winner.

remove the air cleaner and leave the hood up and start the engine.

look at the choke immediately after it starts . . it should be around 3/8" open

open and close the butterfly to see if the engine smooths out . . if it does, simply adjust the choke in that direction.

it is also possible that your vacuum advance is advancing the timing too much so try unplugging the vacuum hose that goes to it also while it is running ad see if that helps.

Great info. from all ... thx

 

[Don C]

While cranking the choke should be completely closed when it is 30°. As soon as it starts engine vacuum should cause the choke pull-off to open the choke slightly.

Let the engine run until it warms up enough to open the choke to see if it smooths out.

 

[naa10104]

While cranking the choke should be completely closed when it is 30°. As soon as it starts engine vacuum should cause the choke pull-off to open the choke slightly.

Let the engine run until it warms up enough to open the choke to see if it smooths out.

I completed the adjustment outlined above and that seemed to help ... will have to try a few more cold starts to make sure. Thanks for the help.