The Stovebolt Site Forums The Shop Area Engine Shop Throttle Linkage

Hello,

I have a 53 3100 truck, with a 57 235 engine. The engine was re-built in '97 and passed down to me. I do not believe the current throttle linkage/return spring set-up is correct. According to my research, the current linkage is for a chevy car. I am running fenton dual carbs with dual exhaust. Based on my set-up, can I switch this to a truck linkage/vertical spring set-up? Will this work with a car engine? I notice at times, that the throttle doesn't fully return to resting. I have attached 2 photos.

Any help would be great.

Thanks

Have you tried running your spring straight down?

You have duals so whether truck or car, it's not original, so you can do most anything even make it cable operated.
I would concentrate on where the problems is. Do the easy things first.
Throttles not fully returning to rest could mean your spring is not strong enough or is located in the wrong position.
You can add another spring.
You can also add individual return springs on each carburetor.

As mentioned above, run your spring straight down. Hook it to the lip of the pan for testing. You can usually find an assortment of lengths of springs at your local hardware store. Get a shorter/stiffer one if you need to.

I have tried a few other springs, and they don't work as well as the current set up. I will try running it down to the bottom by the pan. Should I turn around the linkage bracket and run the spring to the petcock on the head?

If you are running both the Fenton dual carb intake & the Fenton headers...
They make a custom throttle linkage kit that fits that set up perfectly..

HERE...

You have the same problem that I inherited when I bought my ‘52 3100 with a ‘59 235. My engine also came from a car with the linkage from the same. I bought a used linkage, from the gas pedal to the carb. I don’t know what year, but it matched what is shown in the Assembly Manual. Unfortunately none of the linkage from the car was correct necessitating replacement of it all. There is an excellent write up in by a fellow “Bolter” chev235guy about the alternative pivot point used on the truck. [Link]

The pictures are from my engine with the proper linkage installed (except the linkage to the pedal. I included the Assembly Manual page I got my info from to buy replacement parts.

In the pictures note the round head screw. I found that in the alternative position and swapped the pivot for the screw and reinstalled the screw in the old position. Unfortunately access to that area is tight. I found it was easy with the removal of the intake and exhaust manifold.

This info assumes that the Fenton manifold does not block any portion of the linkage.

I picked up a variety of springs and tried running straight down. It did not work well, and the throttle remained open. The current set up works well, but I know it is not correct and to spec. I think I will order that linkage on Ebay that Mother.Trucker recommended. I appreciate all the help and will let you know how it works.

Thanks for all the replies. I looked a little closer, and it looks like the Ebay set-up will not work because of my Fenton dual exhaust blocking where the return spring would go. And I picked up a variety of springs and tried running them straight down to the pan on my current set-up. This did not work well, and the throttle stayed open. Any other advice?

Actually your throttle return spring is improperly installed & it also looks like the improper spring.
The kit on eBay includes the proper return spring bracket that attaches to the original location on one of the oil pan screws.

I did the same set up Fenton intake manifold and Fenton headers I bought the linkage from mother trucker and other parts as well it makes life so much easier just follow the easy directions and you will be on your way.
Not to mention if you buy from joe ( mother trucker) 100% great to buy from and you will get the right parts the first time and fast to ship.

It will fit I did the same set up Fenton intake manifold and Fenton headers the linkage joe( mother trucker) sells will make your linkage so nice follow instructions and it’s done mother trucker is great to buy from you will get the right parts the first time .

Before I bought the linkage from mother trucker my stock linkage was getting hung up about half throttle on the exhaust manifold
I also thought my spring wasn’t returning it back to the idle position

Your bell crank is the issue. I had the same issue where the linkage was getting hung up and going to the stock setup or buying the setup mother trucker is talking will solve your issue as attested to by latroca52.

Do you see the petcock near the bellhousing? That is where the other end of the spring on the bell crank goes, around the petcock. You spring is not the right spring so you will want to get something that looks like the one in Mother Truckers photo. Next, weld a little tab on your bell crank linkage, the linkage that goes straight up to the carbs, drill a a small hole in the tab and install another spring. Run this spring down to the pan and hook it to the pan ledge. The tab is better but in the absence of a lower tab, the pan method will work.

the other thing is that the linkage that connects the two carbs does not have enough slop in it to allow the carbs to fully close. You may have to make up some new linkage that allows for a tiny bit of slop on the part of each carb to get them both to seat completely on just the spring pressure.

Sounds like you need to invite another SF Bay Area Stovebolter over for ideas, opinions, etc. LOL - Though I don't have a dual carb setup, I need to go and see where my return spring is connected down at the bottom.

A few thoughts:

(1) I was unaware that Fenton made carburetors, so no comment on how to hook to the carburetors.
(2) Some carburetors (notably those originally on MoPar products) have the internal accelerator pump spring designed so that the carburetor (without a return spring) is at half throttle! Anytime MoPar carburetors are used, the throttle return spring(s) must be significantly higher in tension to overcome the internal accelerator pump spring(s).
(3) If both carburetors are using chokes (and I highly suggest that they do, MUCH better low end torque by using the choke butterflies as "straightening vanes"), if one of the chokes is not at the maximum opening, an idle screw could be on the second step of the fast idle cam.
(4) I have yet to see aftermarket linkage that I personally like, and make my own, which is much heavier than the A/M stuff. Mine doesn't bind. No, I don't make it for others, don't ask.
(5) We have ALWAYS used a return spring on EACH carburetor. Having a spring on the linkage may never cause all carburetors to return to the idle position.

Jon.

Mother Trucker is mentioned in this thread. Does anyone have a link to Mother Truckers (Joe in Arizona?) (or is it Mother Trucker)? Is there a website? Is it Mother.Trucker? I can't seem to find anything. Thanks.

Regarding return springs: For safety reasons (yours and the engine's) a spring should be attached to each carburetor throttle arm so that should the linkage to one or both carbs become detached, the carb will go back to idle. Otherwise the engine can suck them open to full throttle; I have seen this happen while I was standing next to the engine and could do something about it.. That (these) need not be the only spring(s). You'll still need one on the lower part of the bell crank, in my experience.

For rod-ends I have used Heim joints and threaded the ends of the rods which gives a nice, fine adjustment. You may be able to get left-hand threaded ones so you can make adjustments without disconnecting the linkage come tune-up/carb-sync time. A Heim-joint remedies the usual worn rods and holes in the throttle arms and bell-cranks. Washers can only make up for a little slop. Also try to keep spring tension to the minimum required or with multiple carbs your foot will get tired on a long trip.

Rusty, his username here is Mother.Trucker. He hangs out mostly in the Swap Meet Forum. He will usually respond to PM’s.

Thanks, Martin.

Thanks for the information. I looked at Mother Truckers set up...I don’t think it would work for me based on the lack of clearance behind the exhaust and the block. The spring would not have the space needed...my exhaust is nearly touching the block.

I tired turning about the bell crank and running the spring back to the petcock....this did not work and the throttle would close appropriately

You might use the later chevy compound springs (one inside the other )for a safety factor if one spring brakes you still have some return so it doesnt run off. Then maybe you can still get home !

Fixite- do you have a photo of the compound spring you can share?

It’s nothing special, just a spring like you show with another smaller spring inside it giving a little more pull.

This is how the spring is supposed to be installed. Also, Your spring is not the right spring so it may not have the correct tension. You may also need an additional spring as I mentioned, on the vertical throttle rod. Fenton use to make linkage for their intakes that had the tab already welded, to assist with the upper linkage rod.

Others have mentioned a spring for each carb. That works but if you are using the straight unadjustable rod and tab style linkage (like the offy intakes use) the carbs have to be set exactly the same in terms of throttle arm opening/position or they may not close, especially if one carb is open a bit more then the other. You need some independent adjustment for each carb and a tiny bit of slop in the linkage. Also, it’s easier to synchronize the carbs if they can be independently adjusted.

IMO a properly engineered linkage only requires 1 spring near the bellcrank regardless of 2,3, or 5 carbs. If you need more you are trying to hide shortcomings and stressing out the throttle shafts. Anybody see a spring in my setup?

Curt, can you send a photo of your bell crank spring set up?

I don't have a picture of that area but there is nothing custom about it. Mine looks like the pictures posted by Phak...there's a tab on the vertical rod for one end of the spring and another tab on an oil pan bolt for the other end. Good luck.

This thread sure reminds me of the struggles I had trying to make a rigid linkage work. It kept me awake at night until the following criteria came to me when designing a solution.

My food for thought on this is specific to multiple rochesters on a Stovebolt and not other applications.

1. The accelerator return spring would ONLY have that function and have NO influence on the carburetors whatsoever.

2. The only pressure on the carbs idle stop screw would come from the internal pump spring and free from influence from an external spring, bolt, or other means. The linkage should lift it just as your finger would with no stress.

Accomplish these goals and it’s a zero maintenance item.

Happy new year bolters