My 1920 Canadian built touring car runs pretty good on battery, but when I switch to magneto it backfires and loses power. Any suggestions?
See what the crankshaft end play is and if not excessive try an in car magnet charge. If the end play is excessive you may be looking at having to pull the engine. It might be possible to replace the third main bearing cap in the car to correct excessive end play but it’s not an easy job. Alternatively, you can try using an after market shim behind the pulley on the crankshaft to correct excessive end play. Lots of people run on a 12 volt battery with good results if the coils are properly adjusted and forget about running on magneto until it’s time for a complete engine rebuild.
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Once had similar issue, when slowing on Mag, the engine stumbled, switched to Bat for lower speeds engine fired well. Thought that my flywheel magneto was lacking.
Told this to a coil rebuilder and he said get your coils adj. on a HCCT or modern ECCT that mimics the Ford magneto. Did that, all 4 coils set on a modern unit to fire on time, well that did it! Ran great on Mag, bit less on Bat , but much better than ever before. Didn’t have to recharge the magneto or do engine work.
I had the same issue with my Walkerville built ‘19 Touring. Rebuilt coils helped and so did rebuilt magcoils, but the real issue turned out to be the end play in the crank. Like mentioned above, check the crank endplay. If memory serves, .004 inches is your minimum, .007 is getting close to max. I had .027. I pulled the engine and it’s at a rebuilders.
Checked the end play as per ford manual. Seems to be more that the .015” allowed. I found the shim you referred to, I’ll try that 1st. Thanks for your help !
If you have an analogue meter check the mag output before you do anything so you have a reference point. You can do it while running on battery. If you try using a shim and the shim doesn’t improve the output enough you can also do an in car magnet charge.
Thank you Russ t fender. Ordering an analog volt meter today. Lol I have lots of upholstery tools and wood working tools, but not much for working on cars. Time to start collecting new tools!