Choke/throttle rods set up

Clem Clement

Clem Clement

Well-known member
I've got something connected wrong on my choke/throttle setup. The throttle is very stiff. When the choke is pulled full out for starting, the engine races as the starts. It is a '39 pickup 85 carb # 94, 91-99. The choke does not push full in.
 
Clem the rods on my 39 pkp. Took some tweaking , bending to get to not bind on the new dash grommets . I am still not able to get the throttle to stay where. I want it .Sunshine
 
The throttle on my stock '46 Coupe won't stay where I set it, and returns to idle. Were they ever built to stay where they were set? Can they be repaired to stay set, and how?
 
Same trouble with the throttle on my "36. Somebody said they used a clothes pin to keep it in place. Maybe i'll just do the same. Terry
 
From what I've read and heard, they never stayed in place; always returning to idle. Seen some story about a guy using his company gas card wedged in to it to use a cruise control. Long story short, the card snapped in half and couldn't pay for gas for his return trip...
 
I improved movement through the firewall by bending the rods and putting a little silicone grease on the rod where it passes through the firewall grommet.


Regarding the slipping of the throttle rod, I have a small hose clamp on the back side of the instrument panel grommet that tightens the grommet to rod enough to keep it from sliding easily.


Glenn
 
I find that when the '39 /85 hp truck starts with the the throttle full in and the chock sliding in from full out, it immediately goes to hi rpm? I catch it with the ign switch. The butterflies seem to move correctly. I do not have a elect. fuel pump
 
If I understand your question: When the choke is pulled out, the throttle is advanced and won't release until the accelerator is patted. Sliding the choke to a reduced position won't release the throttle by itself.
 
So, when you "catch it with the ignition switch" have you looked at the carburetor to see what is holding the throttle open? I suggest disconnecting the hand throttle rod completely and just start the engine using the choke and foot pedal and see if you still have issues.
 
Never thought of that.
Today I trued to start the engine to no avail. I primed it and it started and backfired up thru the carb. A couple of starts and hi rev occurred, so I quit.
 
I once had a lawn tractor (Simplicity) that had a push/pull throttle. It had a speed control built into the dashboard mount for the cable mechanism. You could pull the throttle out to your desired engine speed, then lock it in place by rotating the knob clockwise. When you desired to reduce the RPM's you would turn it counter-clockwise to its free position. You could then, push in or pull out as desired. This works similar to a drill chuck or collet, that applies a locking force on the sliding shaft, which is a little larger (about 1/4" OD) than the cable itself. That principle could be applied here to the hand throttle if one could find a mechanism like i described.

Al Hook
 
thanks. I'm thinking a good "brogan maintenance" kick would help as a well.

As a very young pilot flying the BoeingWB-50, we had the props go out of electric sync. The control box had a bunch of spring bells it and lots of electrical contacts to keep the props in sync with the masker. I watched my engineer front his seat reach out an kick the control box. The box went "brrrrrasfwewf" shaking on its spring mounts. The props changed speeds with loud noises and settled back in positions. God love the senior flight engineers!!
 
Hi Clem,

As mentioned above, you need to see what is either hanging up the choke and throttle rods or the position of the choke plate.

I would shut it off shortly after it races without touching the throttle pedal or the choke and throttle rods. Have the air filter off and just look at the position of the carb plate and carb throttle shaft and linkage. Just look at first and if something is not returning you can nudge things one by one to see what's hanging up.


If you don't see anything you may have a large vacuum leak. Turn the idle screws all in and count the turns back them out so you're in maybe 1/2 turn or more in from were you started. Start it up and the RPMs should be reasonable. If not shut it off and turn the screws in more.


You can find the leak using carb cleaner or propane used very carefully, no sparks flames, etc. When you pass say a low puff of propane over the leak source, the RPMs will climb.


Glenn
 
Some other things to consider...after reading the V Tardel's booklet #7 Stromberg 97 there were some assembly tips worth noting and may apply.

My 39 has a Stromberg, there are a bunch of small springs on that carb and a darn $2.00 baby return spring might be it.

Ensure we also do not have some wear in the throttle body bore, binding.

Also the ball ends of the throttle-linkage do wear and can cause binding, sand paper and a small round file to round out the ball if misshapen.

Tighten the choke pivot and levers, and make sure the throttle linkage is @ about 90 degrees. Again this applies to a 97 but probably similar to a Holley.
 
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