Spark Advance Linkage Length

B

Bergy

Member
I'm in the process of trying to find the root cause of my spark advance linkage not fitting properly. My linkage is factory standard of 17" inside-inside, or about 17-1/2" total length with the sliding sleeves. The distance from the inside-inside of the control rod arms on the steering column (down) and the distributor plate fully advanced in the distributor slot is 16-3/4" or about 1/4" shorter than the linkage. The linkage was "bowed to fit" before I started this process, as it was causing inconsiency is setting timing, etc. This is on a '29 roadster, with a 7 tooth steering column.

It appears my solutions are: 1.) find the root cause and fix it (preferred option), 2.) bend one of the control arms to fit, 3.) shorten the linkage by cutting and welding, 4.) leave it as is with a "bow" in the linkage.

Has anyone else had this issue and found a root cause that's easy to fix? Or, is their a preferred option of the other ways to jimmy rig it (no offense jimmy)? I'm leaning towards option 2 if I can't find the root cause.

I have checked to see if there is any misalignment of the engine to the frame, but all seems to be well with the motor mounts & rubbers (albeit they're old). I've also checked to see if there is any way to rotate the steering column, but all appears to be rigid.

Thanks in advance if anyone has any guidance or preferred solutions to this problem.
 
If your car has a 2-tooth steering sector, you rotate the steering column so that the spark rod has proper movement from full retard to full advance at the distributor.
 
As DDW says, Rotate the tube/sleeve of your steering column. Loosen the clamp at the bottom of the column and twist it in the desired direction. It's kinda like the last thing you think of doing, but that's the cure.
Terry
 
Bergy stated "This is on a '29 roadster, with a 7 tooth steering column", so steering column is a NO GO.
I have a '28 roadster with the same problem and the only solution I have found so far is your option 4 - bend a bow in the linkage. With the bent linkage I was able to obtain the correct movement for both no advance to full advance.
J
 
Hello Bergy,

I would go with your #2 method, in fact the service bulletins on page 480 say to do this as long as the distributor body has the correct movement 20* degrees between retard and advance, and the rod is the correct length, (some repops are not correctly made) It took just a little bending to fit correctly when I did mine.
Regards Brian.
 
Last edited:
Thanks to all for your input. I ended up bending the control rod end as best I could, followed by a slight bend in the linkage at the steering wheel end (to match the control rod angles) and finally got the proper travel.
 
I think the control rod is too long. I've noticed that on most of the Model A's I've had. I end up by bowing the rod slightly, on one I must have rotated the column 10 degrees so I wouldn't have to bend the rod but it looked odd from the drivers seat so I just bent the rod.
 
1930 coupe said:
You can order a sleeve to adjust the rod. You cut the rod, install the sleeve and adjust the length and tighten the screws. Most of the parts vendors sell them.
Click to expand...

I was just having this same problem today. It turns out, I had been looking at that brass piece among the parts I got when I bought my first roadster two years ago. I kept wondering what on earth it was for. I just put it to use and am happy as a lark!
 
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