Throttle Linkage suggestions

[JSabah]

I came up with the linkage shown below. I’ve never driven a 40’s or 50’s American car, but to me the gas pedal feels a bit off. I might describe it a heavy or stiff. With my heal on the floor I don’t seem to get enough leverage so I end up lifting my foot and pushing the pedal up higher. Even then it doesn’t feel smooth. I suspect that it is my home made linkage. Issue was that I needed to have it positioned as it is so that it pulls the throttle lever. I made the vertical linkage out of a threaded coupler and drilled out the threads for the vertical portion of the rod (I rounded the top of it so it wouldn’t look like a hardware store part). It is secured to the swivel with a bolt from under, the theory being I wanted it tight to the swivel so there was no play but needed the rod to turn as the swivel came around. One option I was thinking of trying was to leave the coupling threaded and put threads on the vertical rod with grease or anti seize and possibly support my linkage with some 45’s but I was hoping that there is a better solution (suggestions please) ... or is the pedal supposed to feel as I described?  

[greg g]

Might try a cable from the bell crank to the carbs. Too many different force directions as it is. Vibration will likely bring failure of the connecting vertical  to horizontal joint.

[Ed-D24]

Very nice looking engine bay. From the firewall to the 'L' lever attached to the head looks stock - but the big 'Z' rod (with 90° angles) from the lever to the carbs looks 'very custom'. I'm not sure how to help, other than in a purely mechanical way... Try to make that linkage out of a single rod, that has more gradual bends (no more that 45° if possible). I'm not sure if that will fix your problem, but I'm pretty sure it won't hurt.

So, out of the 'L' bracket on the head, make a ~30° bend a bit below the second corner on your current (90° - 90° bend) bracket. Then make a 45°+45° radius bend upward to the 90° to the carb linkage. You can use a tubing bender, but might need to heat the rod a bit to allow for good bends.

I attached a picture of my '48 D24 (the return spring and hand throttle are currently disconnected), but it is a single carb. Maybe try something similar, where you go more stock out of the bracket on the head and then try to make a lever on the two carbs that comes down to the rod coming off of the head assembly. In other words, try to make the rod coming off of the block lever 'flat' like that going to the single carb and then make something that connects the two carbs together.

 

Edited February 24, 2020 by Ed-D24
Realized that he mentioned that it isn't a stock assembly.

[JSabah]

14 hours ago, Ed-D24 said:

Very nice looking engine bay. From the firewall to the 'L' lever attached to the head looks stock - but the big 'Z' rod (with 90° angles) from the lever to the carbs looks 'very custom'. I'm not sure how to help, other than in a purely mechanical way... Try to make that linkage out of a single rod, that has more gradual bends (no more that 45° if possible). I'm not sure if that will fix your problem, but I'm pretty sure it won't hurt.

So, out of the 'L' bracket on the head, make a ~30° bend a bit below the second corner on your current (90° - 90° bend) bracket. Then make a 45°+45° radius bend upward to the 90° to the carb linkage. You can use a tubing bender, but might need to heat the rod a bit to allow for good bends.

I attached a picture of my '48 D24 (the return spring and hand throttle are currently disconnected), but it is a single carb. Maybe try something similar, where you go more stock out of the bracket on the head and then try to make a lever on the two carbs that comes down to the rod coming off of the head assembly. In other words, try to make the rod coming off of the block lever 'flat' like that going to the single carb and then make something that connects the two carbs together.

 

I had a chance to work on the linkage a bit today with what I had in the garage.  Basilisks extended the swivel with a pice of metal and put a twist in it to get a vertical. From there the linkage is straight with a less sever bend in the horizontal. It seems to have less play but the pedal is still stiff (but smoother). Any additional advice? I don’t know how to reduce the return spring tension on the 2 motorcraft progressive carbs (was thinking that might make for a more comfortable pedal). 

 

 

 

 

Edited February 25, 2020 by JSabah

[DJ194950]

How is the pedal feel with spring left off and checked by hand from inside of car using your hand to push and return the throttle pedal?

 

DJ

[JSabah]

On 2/25/2020 at 1:47 PM, DJ194950 said:

How is the pedal feel with spring left off and checked by hand from inside of car using your hand to push and return the throttle pedal?

 

DJ

getting smoother. I found that the rod that goes to the pedal had a tendency of Rotating just a bit but enough that it would bind up in the holes that it went through. In addition, the end by the pedal had no clip and was able to just fall out. I drilled a hole for a cotter pin and used some washers. Doing that made it safer and got rid of binding.  Also, I’ve decided to use the higher hole on the lever that rotates at the carbs (thinking that the higher leverage would be a benefit as well as keeping the rod off the lip of the air cleaner. Finally, I shortened the short rod that runs parallel to the head (just before the rotator) which raised the pedal a bit. Waiting for a new linkage rod to come in the mail before this is hopefully 100% ..... but to answer your question: I don’t feel a difference with or without the return spring. But as I said, it is getting smother and a bit less stiff   

[JSabah]

I decided that the rods were never going in a pulling sutures the ball joing always had some give. While I got it better, I decided to try a cable system. Made a couple of brackets and bought a $15 cable. MUCH happier with the pedal action. 

[Andydodge]

One of the few benefits of a RHD car was the less cluttered accelerator linkage that came straight up from underneath the pedal to a small bellcrank beside the carby, whilst this pic shows the Oz GM Holden  sourced single barrel Stromberg that is/was a common replacement for the stock Carter carby the linkage was essentially the same..........note there nothing going across the top of the engine apart from plug wires..........and that cable system is nice & neat..........andyd  

Edited May 7, 2020 by Andydodge

[JSabah]

Interesting.... but my heater duct is on that side and it is crowded there too. Look at my 1st post pics.  I think that my engine builder should have turned the carbs around and had the linkage more towards the center of the car. But then my fuel lines would have been wrong - always something but I think I’ve got it now.