55.2-59 Carb linkage issue - The 1947 - Present Chevrolet & GMC Truck Message Board Network

**popeyestruck** · Yesterday, 10:21 AM

Ive been fighting with the rochestor bc trying to get it to idle . It idles way too high and wont adjust down around 1200rpm. Ive checked all the usual vacuum leaks etc . When I put the truck together I needed to make my own linkage. The linkage that goes from the bellcrank on the block to the bellcrank on the carb seems like I made it a little too long. Would this keep the throttle open too much? If I turn it down a few threads and shorten it would allow the upper bellcrank to rotate further. Does this make sense? Its acting as if I have my foot on the gas .

**1project2many** · Yesterday, 10:53 AM

If the linkage is holding the throttle open you might be able to feel the pressure on the linkage and on the pedal. Normally old parts will have a little play in them but if there's pressure due to the length of the rod you probably won't feel any play. At the least I think I would disconnect the throttle linkage to see if the engine idled at the correct speed before adjusting it.

Do you have a throttle return spring on the linkage? I believe he original system did use a spring. That might help close the throttle. Have you seen this post?
https://www.67-72chevytrucks.com/vbo...28&postcount=1

If I had to adjust the linkage, I might take some time to install a threaded section like a turnbuckle in order to make additional adjustments easier.

leegreen · Yesterday, 01:52 PM

Too long would hold the throttle open, that makes sense.

Most linkage like that has a Z bend in it so you can adjust the length by bending more or less.

You probably have to take it off the carb regardless, so start by disconnecting one end and see you if can get it to idle down when disconnected. Just make sure you still have a throttle return spring with the linkage off before starting.

**popeyestruck** · Yesterday, 03:30 PM

If you look closely at the third photo you see I threaded the end so I just need to remove the cotter pin at the top and twist the rod to shorten it. Hopefully this is the issue. Ill disconnect it first and work it by hand before I do anything. Thanks to both of you! this carb has been driving me crazy. If I push down really hard on the linkage i can get it to idle down about 100 rpms so I knew I was going in the right direction

Yesterday, 10:21 AM	#1
popeyestruck Senior Member Join Date: May 2022 Location: Longwood 59 chevy Posts: 330	Carb linkage issue Ive been fighting with the rochestor bc trying to get it to idle . It idles way too high and wont adjust down around 1200rpm. Ive checked all the usual vacuum leaks etc . When I put the truck together I needed to make my own linkage. The linkage that goes from the bellcrank on the block to the bellcrank on the carb seems like I made it a little too long. Would this keep the throttle open too much? If I turn it down a few threads and shorten it would allow the upper bellcrank to rotate further. Does this make sense? Its acting as if I have my foot on the gas . Attached Images

Yesterday, 10:53 AM	#2
1project2many Senior Member Join Date: Mar 2012 Location: Lakes Region NH Posts: 3,211	Re: Carb linkage issue If the linkage is holding the throttle open you might be able to feel the pressure on the linkage and on the pedal. Normally old parts will have a little play in them but if there's pressure due to the length of the rod you probably won't feel any play. At the least I think I would disconnect the throttle linkage to see if the engine idled at the correct speed before adjusting it. Do you have a throttle return spring on the linkage? I believe he original system did use a spring. That might help close the throttle. Have you seen this post? https://www.67-72chevytrucks.com/vbo...28&postcount=1 If I had to adjust the linkage, I might take some time to install a threaded section like a turnbuckle in order to make additional adjustments easier.

Yesterday, 01:52 PM	#3
leegreen Registered User Join Date: Mar 2022 Location: Surrey BC Posts: 946	Re: Carb linkage issue Too long would hold the throttle open, that makes sense. Most linkage like that has a Z bend in it so you can adjust the length by bending more or less. You probably have to take it off the carb regardless, so start by disconnecting one end and see you if can get it to idle down when disconnected. Just make sure you still have a throttle return spring with the linkage off before starting.

Yesterday, 03:30 PM	#4
popeyestruck Senior Member Join Date: May 2022 Location: Longwood 59 chevy Posts: 330	Re: Carb linkage issue If you look closely at the third photo you see I threaded the end so I just need to remove the cotter pin at the top and twist the rod to shorten it. Hopefully this is the issue. Ill disconnect it first and work it by hand before I do anything. Thanks to both of you! this carb has been driving me crazy. If I push down really hard on the linkage i can get it to idle down about 100 rpms so I knew I was going in the right direction



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