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Expert
Posts: 1730
   
Location: Michigan | So I put a 4bbl carb on my 55 Chrysler when I did the engine but I knew I was going to have a issue with the Travel capabilities of the 55 Linkage.
The system is designed for the 2bbl carb and it moves like only 1.5 inches of travel. I can just crack the secondaries with the pedal to the floor.
The system is based on a floor mounted foot pedal that has a lever sticking out through the floor pan connected to a rod the pulls on a pivot mounted to the firewall. This has another rod that goes to a junction on the engine that has another rod going to the carburetor.
The system has limitations and I have tried to modify the junction on the engine to increase the travel with some success, but it's not enough. I can never get to full throttle with the stock setup.
I have looked at this setup on ebay, summit racing, etc. http://www.ebay.com/itm/BILLET-ALUMINUM-FLOOR-MOUNT-GAS-PEDAL-BLACK...
But before I go down this full modification path I thought I would see if any of you have come up with creative ideas on how to modify the stock pedal linkage to accomplish the travel requirements of the 4bbl carb. |
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Expert 5K+
Posts: 8445
 
Location: Perth Australia | Without seeing (or knowing) how the 55 might be different, you should be able to increase the pull on the carby by lengthening the arm on the bell crank (the arm that the rod from the carby connects to) or shortening the one from the pedal
Just note that either way will increase the force needed to operate the throttle, so be careful of how strong your return spring is
The other way is to get the actual pivot in the carby closer to the throttle shaft, but this is not possible most of the time
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Expert
Posts: 1730
Location: Michigan | here are some pics. note the extension in the second pic. This is how I got full travel on the primary circuit.
Edited by Beltran 2015-04-09 6:16 PM
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IMG_0396 (480x640).jpg (165KB - 79 downloads)
IMG_0395 (480x640).jpg (179KB - 83 downloads)
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Expert
Posts: 2196
Location: Muskego, WI | I ran into the same issue with my 1956 with 354 Hemi. It originally had a 4 barrel, but I lost the original mount for the bell crank (shown in your first picture) when I went with the Hot Heads dual plane aluminum intake. The bell crank originally mounted on the last two intake manifold bolts, but I moved it toward the carburetor one bolt so it bridged the gap between the last and 2nd to last intake manifold runners. I then made all new linkages from 1/4" stainless rod and heim joints, that took a TON of slop out of the original setup. The travel seemed to work out, but I did have to do lots of adjusting for everything to work properly. |
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Expert
Posts: 1730
Location: Michigan | I did resolve this. I converted it using my existing pedal. I just bent the arm of the pedal so it was nearly straight and this gave me all the travel I needed. I then crafted the mounts for the cable under the car and the one off the carburetor for the top side cable. I left the linkage in place as it controls the kick down system still. Still working out the adjustments on that. I think it is too reserved and would love for it to kick down into first gear if I can work that out. It seems to do the 2nd gear downshift ok. I can't seem to get it to hang onto first gear when accelerating with the pedal to the floor. More tinkering required.... |
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Expert
Posts: 2196
Location: Muskego, WI | I don't know how mine works yet, haven't driven it. But when I do I'll let you know what kind of luck I've had. I adjusted mine so I have maximum trans pressure when the carb is at WOT (versus minimum pressure when the carb is at idle). |
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4bbl throttle travel on a 55 Chrysler
