Get out your meter. If your v/r has been tweaked to charge that 8v battery, you should see about 9.4v. If you see 7.2v or so, your v/r hasn't been tweaked & that 8v battery is no better than the 6v battery that is supposed to be there. And, tweaking a v/r isn't all that hard as long as you are prepared for the consequences of failure: a boiled battery, burned up v/r or no charge at all.
I'd clean all the grounds, replace the battery cables & either convert it to 12v or get it back to 6v. That 8v battery is going to burn up your points & lights &, if it's a frontmount, probably your coil as well.
It works like this.......technology & materials being what they were in the 30's, that square coil would melt if it ran on much more than 4 amps for any length of time. (see tip # 38 for an example). In order to get a hot spark at the same time the starter was drawing max current from the battery, a ballast resistor was added in the ignition circuit. What that did was add about .3 ohms of resistance in the circuit, added to the 1.5 ohms of the coil. That got you 3.5 amps or so at start up. As the voltage increased when the engine was running to about 7.5 volts, the resistor heated up, adding more resistance in the circuit. 1.0 ohms hot, plus 1.5 ohms of the coil got you down to 3 amps or so to keep from melting the coil. The same rule (actually, Ohm's Law) applies to a 8v circuit. I= E/R. Current equals voltage divided by resistance. So, 9.4v divided by 2.5 ohms gets you 3.76 amps. The difference of nearly 1 amp means more heat in that front coil.
And, the increase is worse for light bulbs.
Now I'm sure we will hear from folks who are using 8v batteries w/ no problems. That's not unheard of by any means.....but why bother?
Here is a classic example of fixing the problem instead of band-aiding a solution:
From a post on 12/31/07:
“My starter motor quit turning the engine over. There was no click or anything on my 1947 2N.
I could hand crank the engine fine.
I got some new battery cables and cable to the starter which fixed it.
It really cranks up well now. I've got the original 6v system, and with the new cables it cranks up like it did when I had to jump it from a 12v back when I picked up the tractor from my grandfather earlier this summer.
It starts up immediately. Previously it had the original 1947 cables, which upon inspection had the inner strand wires corroded/severed.
Some of you guys thinking of doing a 12V conversion, if you don't need the 12V for some other electronics, might just need replacement battery cables.”
50 Tips
