Inliners International Forums General Discussion Engines Throttle Linkage on Chevy 250

I’d appreciate suggestions from anyone on how to set up throttle linkage on my ’56 Belair. I have a Chevy inline 6 cyl 250 engine with dual Carter Weber carbs on an aluminum Offenhauser intake manifold that I bought from Tom Langdon. Also have exhaust headers installed. The picture below shows how it is currently installed. The original throttle linkage for the ’56 will not work. If you have any pictures of a good way to do the throttle linkage, please let me know. Thanks, TexBA (Glenn)

I had those on my '64 van. are you pulling front to back? mine would never work right pulling front to back, those carbs are around 110 degrees from idle to wot so it was restrictive on either extreme. ended up buying the linkage kit and pulled side to side and used a cable but sure you could fab a bell crank and use your linkage with it. vacuum port from any of the plugs on intake.

110 degrees from idle to wot

That's about 25 degrees too much.

the angle at either extreme was too much to overcome. with the steep angle off idle, I had to really push and once started, it would go to the floor. not very safe! move the linkage the other way and it was fine on the bottom but never got full throttle. the side pull linkage corrected all that but I removed them later for bigger webers. probably have pics somewhere.

It's a geometry problem, the leverage between pedal travel and throttle shaft rotation is off.

This is how my linkage works. Parts came from the GMC,40 Chevy
and the three Weber 32/36 carbs. It is similar to the original linkage.

I kept the rod going from the 40 Chevy gas peddle, but had to ad an inch to mate with the GMC pivot linkage which swings in a bolt in the center of the block. The pivot link has two arms 90 deg. apart that hang below the pivot bolt.The two arms are about 2 inches long. The pivot linkage looks like an upside V with the pivot point in the center.

The gas peddle rod is connected to the closest pivot arm. A vertical rod is connected to the other pivot arm. When the gas peddle is pushed down the vertical rod goes up to activate a long rod the runs parallel to the valve cover. This rod pivots on tabs mounted to the three intake runners

The direction of rotation changes here. The rod has four arms on it. One is about 1.5 inches long and connects to the vertical rod. The other 3 arms came with the carbs. and are about 3 inches long They are finally connected to the Webers by adjustable rods that push the carbs. wide open.

My carbs are mounted at 90 deg. to the valve cover so the linkage has to push them open. They open fully because a small movement of 1.5 inch arm is amplified by the 3 inch arms pushing the carbs open.

the 32/36's are not the same as the carter/webers but using a bell crank and running in parallel as you did would definitely help. the issue wasn't the amount of travel but the angle at which it pushed. at 110 degrees rotation, optimal would be 55 before and after but even that meant excessive force to get over the hump and again for wot. in series, 35 degrees at idle "worked" but left 75 for wot so full throttle never happened. in parallel, 55 was easier but still had issues. 45 was what I settled on and used 'most' of my carbs. linkage binding was less of an issue too. of the old carbs I had laying around, several where 78 degrees and one was 60, not sure what the true webers are but much less than the carters. bought the 32/36's and all those problems went away. 38/38's already on there way here.

"110 degrees" of rotation runs from completely closed (they never completely close) to 20 degrees after fully open - beginning to bend backward and close from the other direction.
Do you mean "clock position"?

360 being a complete circle. regardless how it is clocked, there was still 110 from idle to wot. 90 being straight up, that leaves 55 before and after. the only way to truly overcome that issue (that I knew of) was to install grooved semi circles and a cable but it was easier to just buy different carbs.

I am with panic. I am not following the idea of 110 degrees of rotation on the throttle blades. There's only 90 degrees between fully closed –– to fully open | and with the curb idle screw holding the blades slightly open there isn't a full 90 degrees.

Travel is whole other kettle of fish - that is a function of how far from the center of rotation the linkage attaches - which translates into partial travel along the circumference of circle.

If we are talking about clock face degrees - then I get it. On my dual Carter setup I attached aluminum discs to the throttle actuators. This provides mechanical advantage/leverage - but also increases travel which slows tip-in when the gas pedal is applied. My heim joints are anchored between 95 and 100 degrees (where 90 is 12 o'clock):


But to panic's point the further beyond 12 o'clock one attaches (the linkage) the further from 9 o'clock that WOT occurs.

the carter webers were progressive 2 barrels. unlike a 4 barrel, it was not connected directly to the butterfly shaft. carbs are long gone but do remember it being a full 110 degrees to open both butterflies. neither butterfly turned 110 but the center pivot did. I made the discs just like yours, marked 0-180 and verified total degrees from idle to wot. the fulcrum and linkage to each butterfly was part of the carb and not easy to modify. they were less than $200 for the pair so I just jumped ship but not before making several sets of arms based of the original disc and each time, I verified it was a full 110.

https://www.piercemanifolds.com/category_s/226.htm wasn't a center shaft as I stated but same idea. connecting to part #60, it will rotate more than 90 degrees without fully opening both butterflies.