I'm running a carbon-brush "accurate" timer, I see a bit of erosion at the foot of each contact, doubtless caused by arc-ing. I could turn the contact surfaces smooth on the lathe, but I know the junk lathe and the three-jaw I have are not spot-on.
Much attention has been paid lately to the importance of centering the timing gear cover over the cam, so the commutator will run true, and not in ellipses. Does anyone know just how much tolerance there is for accumulated error between rotor, timer and gear cover without being too far out of concentric? (by the way, the centering tool was round, and the rebate in the gear cover out of round by probably .003")
Thanks for your input !!
Does this help:
Hi Bill, yes a little I think, if I'm reading the drawing right, it's showing the effect of being 1/8" off center ? I'm wondering how much is too much. At worst I might end up .012 - .014" total run out, nowhere near .125" !!
My guess is that centering is most important with roller and flapper timers, and that with a brush type like a New Day it would have to be way off center to have any noticeable effect. I'm not familiar with the Accurate timer, but if it's similar to the New Day I would think a smooth surface is the important feature to have.
The best centering tool fits in the same circle as the timer itself. The small one which fits in the circle made for the seal is not as accurate as the large one.
The New Day type timer would be least affected by being out of center. I don't know about the newer brush type which runs on the outer rim of the timer.
If you are running on magneto, try to set your timing lever in the middle of the node where the engine runs best. If you are running on battery or if you are running at the edge of the node, you will be more likely to have arcing which would erode the insulation.
You would also not have arcing which would erode the insulation if you run an Anderson type flapper timer.
Hi rich i was running a tw timer on my car and the car wasn't running right and when i pulled the timer off it also had erosion in the same place now in saying this my mag plate was not working and since i have pulled my engine out i think the cause of mine was a bad earth but not 100% convinced but pretty sure that was my problem.
i hope this helps
The timer I have, the carbon brush rotates on the radius of the camshaft like the "stock" Ford timer roller. In fact, the timer body itself looks almost the same as the "stock" item.
I'm beginning to absorb the wherefore of the diagram Bill posted - my question is, how much off-center can the timer body be before the erratic early/late cycle affects performance ? I'm remembering Wayne Sheldon's testimonial that an off-center timer caused his T to burn valves.
Also, it's easy for me to see now how I "got away with" a very probably off-centered timer back in my youth, when I somehow skipped that detail in the repair manual . . . I ran a New Day timer with good results. Seems to me the New Day would eliminate the necessity of centering the timer body ?
Yes, the New Day and others of that style are Much More tolerant of an off center cylinder front cover.
To answer your question of how much off center before it causes trouble?
I don't know, but, the less the better. With a centering tool you can be spot on. Good luck with your project. Bill
(How much Not Dead would someone want to be? A little bit not dead or completely not dead?)