[zippy]

I have welded up my slot on the dizzy to limit max advance. At present I have 20* mech adv. I want to add a few more. Does anyone know how much to file for x deg? Say I want 3 more deg total. Is it like .005"/deg or measurement like that?
So I don't have to pull my dizzy apart a ton to times to file and try and re file

[dataway]

I designed and 3d printed this gizmo for checking mechanical and vacuum advance limits. Scale attaches where the points go, pointer slides over point cam.

I think there may be commercial items that do the same thing.

[peters23]

A little trigonometry to the rescue.
Measure/guestimate the radius (shaft center to slot end), multiply that by sin(1), which is 0.017, to get the approximate amount to remove per degree.
Its approximate because the slot is typically not concentric to the shaft, but at its own angle, which complicates things a bit further.

[mgarblik]

Originally Posted by dataway

I designed and 3d printed this gizmo for checking mechanical and vacuum advance limits. Scale attaches where the points go, pointer slides over point cam.

I think there may be commercial items that do the same thing.

That is really slick! There is probably a small market for that.

[Shiny]

On my points distributor, it was an estimated 0.0125" per distributor degree.

My slot length measured 0.375".

With a pin/bushing diameter of 3/16" (0.1875) I had 15 degrees at distributor, which was higher than my target.

I used a Moroso press-on bushing, with 0.25" OD. This resulted in 11 degrees advance at distributor, 22 @ crank, and I called it good.

[70GS455]

Dollar store protractor and piece of wire

[dataway]

70GS That's pretty freakin clever there.


If anyone wants the 3d print files for my creation you can find them here:

https://www.thingiverse.com/thing:5880280