The dirt late mode I help on has a magneto in its kinda of rare in late models now most run a distributor but you need to have an alternator if your going to to run a distributor as mentioned above. Our rules are to wissota which has a rom chip limit but its not possible to have a chip in magneto. If it was being teched they could look at the digital tel tach in the car and see what rpm was hit.
now sprint cars ofcourse run magneto since they ofcourse have no battery or starter. Same with midgets and pavement super modifieds.
While we are all on the subject...
T/A and T/F cars run mags because when you are trying to ignite 60+ pounds of boost full of methanol or nitromethane fog, you need all the spark you can get. But what is with the BOXES? I thought mags were self contained.
This post jogged my memory, My father gave me a magneto and showed me how I could trick my friends. He had installed a small light. The object was to crank the mag fast enough to turn on the light.
The trick was to turn the mag by inserting a metal handle into the output socket on the rotor. The handle had a short rubber sleeve just long enough so that I could crank enough to lite the light. I didn't tell my friends the secret. Shocking
In reply to ebonyandivory :
I’ve raced a lot of cars with magneto’s. My first was a Offy powered sprint car, They would push start me in gear and once the oil pressure was up I’d flip the switch and off we’d go.
The Chevy V8 sprint car was the same. The trick was to keep the car straight while the tires were dragging until the speed was sufficient to get the engine rolling with the monster compression we used - 13/14 to 1 to start and later 14/15- to 1
My MGTD used a vertex magneto several times but the load on the camshaft was too great. We started out with the usual bronze gear but splash oil was insufficient to keep from stripping the gear. Switching to steel the gear lasted a bit longer but chewed up the drive gear on the camshaft. I tried to squirt oil to the gear assembly but the loss of oil pressure wound up hurting the rest of the engine.
I needed to get a bigger oil pump to have sufficient oil volume not to hurt the rest of the engine. At that point the mechanical issues outweighed the benefits and I went back to the points.
We raced most cars without a charging system. A freshly charged battery would typically last a weekend. The weight and drag of a charging system was a happy reduction.
In reply to frenchyd :
Ya know, I hadn’t thought of how starting a magneto fired engine could pose a problem (especially with high compression engines or ones with a lot of rotating mass).
Were they dumping compression during starting the bigger engines somehow? When manually starting an old propeller airplane, overcoming the compression with human power must’ve been tough
In reply to Knurled. :
I think certification costs are so high, and sales volume so low that it's hasn't been economically feasible to change.
You'll note the prevalence of various EFI systems in the kitplanes market.
In reply to gencollon :
I did specify certified... 
I Was also holding a joe Hunt Mag once and My Brother asked to see it, I handed it to him so he would grab the Cap, and well just HAD to give it a Spin, lit Kenny right up, Had a Sportster with a Mag NO starter No kick Start either, Used a Generator with a Volt reg. for the Lights.
The FAA Stoped H-D from using them because it interferred with Tower radio Comm. which didn't make sense to me Because Airplanes used them.
In reply to ebonyandivory :
Compression on older prop started engines was low enough that it wasn’t that hard to do. In fact I once hand propped a 7 cylinder radial but larger than that it was impossible to hand start.
Compression release wasn’t possible on sprint cars
Vintage sports cars running 13-1 compression could be started with modern gear reduction starters. Once cranking speed got over about 200 rpm the spark generated was sufficient to ignite the fuel mixture.
Because we used gas instead of alcohol things were easier than the flooding of fuel required with alcohol.
In reply to Knurled. :
Every airplane that has taken off has landed. 
When we were running a big block modified with a mag, starting consisted of cranking until oil pressure then switch on ign. The starter had to work really hard but it never failed. Had to be sure the battery was up to snuff.
Now most run an alternator and electronic ign.
NickD
PowerDork
8/1/19 3:11 p.m.
Was just operating something with a magneto last night. The old wood splitter that my grandfather built back in the sixties, with a big 1940s single-cylinder air-cooled Wisconsin with a Wico magneto. And then I broke it. We rope start it, with a rope wound around the crank pulley. It kicked back, yanked the wooden handle through my fingers (Ow!) and then started whipping that thing around, snagged the throttle cable and ripped that off and then continued to wind it all inside the engine shroud. *Sigh* Gotta say though, for a guy who had only a middle school education and who built that wood splitter out of cast-off parts (Narrowed I-beam axle supports it, Wisconsin engine came off a generator and he had used it on a lawn tractor that he built from scratch, pusher was an outrigger of a scrapped Case backhoe) that thing beats the E36 M3 out of any mass-produced or home built splitter I have ever used.
In reply to ebonyandivory :Inconsistent as Hell
ChasH
Reader
8/1/19 10:07 p.m.
GTXVette said:
I Was also holding a joe Hunt Mag once and My Brother asked to see it, I handed it to him so he would grab the Cap, and well just HAD to give it a Spin, lit Kenny right up, Had a Sportster with a Mag NO starter No kick Start either, Used a Generator with a Volt reg. for the Lights.
The FAA Stoped H-D from using them because it interferred with Tower radio Comm. which didn't make sense to me Because Airplanes used them.
Aircraft (and military) ignition systems are shielded to eliminate radio interference.
A friend did the magneto test with another who promptly dropped the magneto, which belonged to a rare '52 Indian 500cc twin, and destroyed the irreplacable rotor arm. I made a replacement from pieces of plexiglass laminated together.
Super handy when you don't need or want a battery or other electronics. Also when fuel mixtures are very, very stupid (nitro based classes). Other than those reasons there are better answers than a mag. Even on the spark power side some of the latest inductive ignitions are approaching all but the very, very best of magnetos with very little downside.
noddaz
SuperDork
8/2/19 9:17 a.m.
He had a magneto on it. He said he was playing with it one day, holding the mag in his hand and just kinda spinning it until it shocked the E36 M3 out of him.
I have heard of people doing this. Unfortunately, that is really all I know about magnetos.
Scott
Magnetos are great, but do have higher resistance to rotation so place a bit more load on whatever gear is driving them. If that gear is in the middle of a shaft that is located at each end, no big deal, but if the mag is running off a gear at the end of a shaft that is only secured at one end you are going to get more side play and wear on that drive gear than a distributor does and may have reliability/wear issues.
