This was the first mag gap set up for me and was it ever time consuming. I turned the engine on it's nose and was trying for .028 on the upper and .034 on the bottom. the best i could get on the top range from .029 to.031 and the bottom gap is .033 to .036 I'm not to concerned about the upper gap but is the lower .036 getting to far out ? brass feeler gauges are pricey so i used a couple of mag shims and pealed them to the desired thickness. thanks. Ken
The Ford repair book says that the mag should be not less than .o25 nor more than .040. Your settings are fine.
I'm not opposed to use whatever works but for $4.76 you can get a brass feeler gauge at:
If your gap is within the recommended 0.025" to 0.040" range you should be good to go.
Tom tested different gaps and it still worked up to a gap of 0.160" (four times the 0.040" recommended limit). For details see:
When I converted a '15 to starter I think I spent about 4 hours setting the mag gap. Maybe more.
But I got the all at .025 or close.
I had a '22 that was professionally rebuilt and the mag would rub when the motor warmed up.
It touched in two places.
Pulling the engine to adjust it was not a lot of fun.
Thanks for the info guys, I have the model t service manual but the concern i had was the variation in the gaps.I guess the small plus and minus gap don't mean that much. Hay Jim, If i would have seen that gauge on ebay i would have ordered one but after using the shims as a gauge I didn't have to stack blades for the thickness. Ken
The variation in the gaps is fine as long as it falls within specs.
I seem to remember Bruce telling me that 0.025 at the top but up to 0.040 at the bottom as the transmission will sag and raise the upper and lower to bottom.
I used steel feeler gauges on all my 3 Model T's and the magnetos work just fine.