1957 Ecode carburetors won't idle below 1000 RPM

[ron57]

Had carburetors built on 57E code but can’t get idle below 1000 even with throttle all the way down,

 

[Ward 57]

Had carburetors built on 57E code but can’t get idle below 1000 even with throttle all the way down,

Are you sure you have the linkage adjusted right? I don't have the specs but there should be just a little free wiggle when at rest. It's a feel thing to check for any even minimal binding and any joints that don't have a touch of free play

 

[ron57]

Thanks Ward57for your response. There is some play in the linkage but high idle persist even when running idle screws are not even touching posts.

 

[Ward 57]

Thanks Ward57for your response. There is some play in the linkage but high idle persist even when running idle screws are not even touching posts.

I'd then look to see if one of the butterfly flaps are not closing all the way. If recently rebuilt, the shafts and flaps may not be mating correctly into the throttle body and binding slightly open. Do your investigation. Just a tap of the butt of a screwdriver on the flapper should tell you if it's not seating on it's own and if you had them rebuilt the rebuilder should be able to figure it out. Subtle but makes a big difference.

 

[74 Harley]

It may help to disconnect the throttle linkage. It may be too short.

 

[ron57]

I'd then look to see if one of the butterfly flaps are not closing all the way. If recently rebuilt, the shafts and flaps may not be mating correctly into the throttle body and binding slightly open. Do your investigation. Just a tap of the butt of a screwdriver on the flapper should tell you if it's not seating on it's own and if you had them rebuilt the rebuilder should be able to figure it out. Subtle but makes a big difference.

Butterfly flaps are definitely closed, l can hear them seat. I’ve read it could be a vacuum leak which I’ll have to check for. I also have to connect a vacuum tube between the two carburetors. Since I didn’t have this issue prior to rebuilding I’m wondering if it’s possibly main metering jet.

 

[74 Harley]

Over size main jet will make it run rich, not a high idle. Since this is a new problem I too suspect a vacuum leak.

 

[jimntempe]

If these have a fast idle screw for when the choke is on make sure that didn't get turned in to where it's overriding the normal base idle screw setting. Or that the linkage between the choke and choke fast idle cam isn't messed up keeping the fast idle cam "up" in position even when the choke is off.

 

[doug7740]

It sounds like you have a vacuum leak behind the choke plates where the throttle body meets the main body.

doug7740
1955 Thunderbird Blue