Mag questions

I'm curious about magnetos. I love their look and I know the general principle and application, but I wonder if it's something I'd want for my early 331 hemi.

Can anyone answer a few questions?

1. How exactly do they work?
2. What limitations do they have?
3. How hard is it to find one for my motor?
4. What should I look for in a mag?

Thanks ahead of time for y'all's help and maybe some other folks are curious, too. Looking forward to some good info!

STONER

 

Check with Joe Hunt... they make one for the SBC that looks like a mag... but has an electronic ignition hidden inside. Maybe they could whip one out for you... or better yet, maybe you could make one yerself and post the how-to here for us to see!

Sam.

 

I can answer question one. There are spinning magnets inside of the magneto. Those spinning magnets have a magnetic field, and when they spin around they energize wires inside the magneto. That then send that electricity to the spark plugs. After some points control it, and a condenser I think.

 

Dehudso pretty much nailed number 1.

2. The size of the spark is relative to how fast they spin, so they don't put out a lot of spark when cranking. This can make it hard to start a car with a mag.

You can't run a normal tacho with a mag. You can get tachs that are designed for them, or get a mag with a cable tach drive.


3. There have been plenty of race Hemi's built, so it probably isn't too hard to find a mag for one. Unless they use permanent magnets (newer models only), they lose their magnetism over time, so a mag that has been sitting around for a while would need to be sent to a mag shop for a freshen up.


4. Because they are generally race only, they are often locked at full advance, which won't work on the street. Some will have a centrifugal advance, which would be ok for street use.

They use points and a condenser, so these need to be available. Ditto for the cap.

 

i can't think of anything more lame than an ignition system that costs MORE than a magneto and doesn't work as good, and is less reliable. the HEI magneto lookalike things are dumb.

your standard scintilla mag, marketed by joe hunt, vertex, ronco and a few others are pretty much all the same. they weren't exactly intended for use in race cars, more of a universal ignition system for airplanes and such. they last forever, with almost no maintence.

the only thing bad about one that i can think of is they don't have a very high output during starting and low RPMs. not generally a problem though.

good luck finding one for a 331. i've personally never seen one for sale. SBC ones are super easy to find though, and someone makes and adapter to stick a SBC distributor in an early hemi. makes things easy... David

 

hunt has them and they are not that expensive. Hunt wanted $750.00 to rebuild mine and when they were done the bill was only $550.00 what a deal huh!!

 

I bought one for a 331, off this board a couple of months ago. It's going in a Hemi powered model A. Dean

 

Thanks, y'all.

Now, I'd really like to find one. Any details on the adapter to fit an SBC model to an early Hemi--manufacturer maybe?

And how hard is it to crank a motor outfitted with one? That doesn't really scare me at all, but I do want the damn thing to start before I kill the battery.

Finally, anyone have one for sale? Or can you point me in the right direction?

One more thing--do you have to consider different wires and plugs with a mag setup?

Thanks again, y'all...

STONER

 

Since this is Tech week school me, on wiring one up.

I've got a Ronco MAG for a BBC and I want to use it, if I understand how a Mag works the ignition is self contained how do you shut the engine off, How would you wire it so shutting off the ignition switch would kill the igniton.

 

you won't have anyproblems cranking over a motor with a magneto, unless you have some ungodly compression ratio of like 14 to 1, and are dumping in 90% nitro.

the easy way to wire it into the car is with a toggle switch, to kill it. just run the wire from the post on the mag, to the switch, and then run a wire from the other side of the switch to ground. If the switch is open, the motor runs, if it's closed, the post on the mag is grounded, so you get no spark. if you must use your existing ignition switch, things get a bit more complex. you need to use a relay in place of the toggle switch to ground the mag when the igniton switch is off. use the wire that currently goes to the coil to power a big beefy normally closed relay. normally closed means that the contacts are closed when the relay is not powered, and they are open when it is powered. so when the igntion is on, the contacts open up, and the mag isn't grounded. the igntion is off, the points close, the mag is grounded.

for most, if not all magnetos, you need to run solid plug wires, not resistive ones, and non-resistor spark plugs. you have to narrow up the spark plug gaps a bit too, so the motor will idle at low speeds, or it might have a problem firing the plugs at low RPM. David

 

Thanks David, good tech info.

 

STONER:

One more thing to add:
Your Spark-Plug gap needs to be .018-.022 with a MAG.
I would recommend CHAMPION plugs, the NEW designs of today are what Champions Win with every weekend.

 

Wow--this is some great info! I've seen several mags for sale that are said to be BBC setups. Are there adapters to make any mag work with any motor?

And I actually like the idea of the toggle, since my plan is to use toggles in the car anyway.

One more question: What about a tach?

 

SBC and BBC distributors are the same. If you found one, it'll work in either.

 

I had a Vertex magneto for a SBC, and sent it in to Vertex and they converted it to 390 Cadillac. My mag turned out to be bad...so Ted at Vertex basically sold me a brand new mag for $580...Vertex is about one of the best companies I've ever dealt with....

 

Oh yeah...I almost forgot...Ted at Vertex told me that Joe Hunt magnetos are actually Vertex mags...Joe Hunt just puts different magnets in 'em, and then changes the nameplate....

 

[ QUOTE ]
Wow--this is some great info! I've seen several mags for sale that are said to be BBC setups. Are there adapters to make any mag work with any motor?

And I actually like the idea of the toggle, since my plan is to use toggles in the car anyway.

One more question: What about a tach?

[/ QUOTE ]


Hunt can change the base to whatever for you. You will need a cable drive tac.

 

PAW' Hemi catalog lists a Vertex race mag for $995, plus wires.If you don't have their catalog you should -- 818-678-3000.

 

you should also look for a mag that does not have the advance fixed. if you do run a mag with a fixed advance it is better to use a toggle switch then a relay. it will start easyer if you crank it over then flip the switch to unground the mag and it will always start right up

 

i have also used a 15 second delay timer with a relay for starting