Flathead mag for the week "Vertex"

BUBBAS IGNITION

BUBBAS IGNITION

Well-known member
There has been lots of discussion on using a Vertex magneto on the street.
My job of the week is a vertex for a flathead to be driven every day and we have a few of these out there running very well.
First of all lets take a used Vertex ( hopefully in good condition which we will check) and test it on the machine. My concern here is for a good strong steady spark at low rpm ( concerning cranking speed etc). This one passes !! Point gap is verified and adjusted if needed.
Take mag lower end off ( Chevrolet lower end , mag is correct rotation for Flathead) . Special driver tool is needed ( may be made with old screwdriver).
This one has no brass advance weights in lower end meanng it has NO advance ( discussed in a minute)
I call the lower ends a "butt" and i have machined flathead lower mag butts in stock most of the time.
Install drive shaft ( also machined for flathead cover and drive gear ) and then install lower end to shaft and tighten hold down screws with locks etc.
And wall-ah you have a fairly cheap method of owning a flathead Vertex unit...
Absolutly the " hottest" spark you can have in a flatty!!!! Gap the plugs at .025 and let er rip !!!!!
 

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BUBBAS IGNITION, I have been told magbeto's run hot like a elect. motor. I had a top half of a Joe Hunt mag. mated to a 58 corvette lower half , the bottom half ran the fuel pump with a cable I LOVED it ,and would like a mag for my 8ba flathead. Harold central coast Ca.
 
No doubt a mag looks cool, but why would anyone want to run one on the street with no advance mechanism?
 
Answer to the above :

Theres really no reason a guy cant run a magneto ( other than cost $) the Vertex mags are very well built with bearings etc. The rotating assemblys last a long time and do from time to time require some maintenance. The only downside is that the magnets do with some time and heat cycles loose some strength.
However this maintenance is really no worse than a contact point system.
The heat doesnt seem to be a issue and the flathead is mounted up front next to the fan air for cooling etc.
The plug gap is a common misconception , plug gaps were widened allowing a longer spark duration needed with lean air fuel mixtures. Most flatheads dont fall into this lean emission problem .On our dyno runs ( with a Vertex flathead) there was hp gains at .025 and a loss with .035 etc.
The mag makes a huge amp spark with a current increase with rpm.

I have found that running a Vertex ( with no advance) that advancing the mag to 18-20 degrees at idle works very well in all rpm ranges. The only issue becomes cranking the engine to start, you crank the engine and then turn the mag switch on to start. This way you have 20 degrees at idle and 20 degrees at 4000 rpm. Seems to work very well.....The engine runs cool and you still have all the adjustment you need.

There would be no problem in buying the Speedway moors mag , it is a real Talor/Vertex style magneto. ( not to be confused with the mag look a likes )
 
I'd always heard that the narrower spark gap running with mags was partially due to lower spark output at slow cranking speeds....at least it was when kick-starting my old Sportster!! Fire every time at .020-.022, but widen it out to .030 and you could kick all day....
 
Aircraft engines were mated to magneto ignitions from the start. They are the perfect system for an engine that stays at basically the same rpm all the time. On airplanes you vary the rpm for take off, landing, & various slow flight attitudes but mostly high rpm in the power band. Many piston engined aircraft also have variable constant speed propellers that will maintain a set rpm for near the whole flight using a governor. The magneto ignition is at its best in this use. They will run in an automobile while varying rpms through a broad range but lose a lot of engine efficiency when city driving or up & down a lot of hills. I think you would find that the engine would overheat more easilly in these conditions while running a mag unless you could rigg a way to vary the timing like the old Model As did. Manual retard and advance would get old if you had to do it a lot but it would work.

Magnetos are married to the internal timing of the points to the e-gap of the rotating magnet, where the spark has to occur, to be at peak efficiency. If you try to move the internal points plate to open the points sooner or later away from e-gap it will really die out fast so the only way to vary timeing is by moving the whole unit in time with the engine.

For starting aids, aircraft use high energy spark vibrators like the Slick Start and TCM -Bendix Shower of Sparks set ups. They run a high energy flux flow through the magneto coil with a set of special retard points timed into the system. These give a high energy start at near 5 degrees BTDC for starting only. They are wired to the start relay so they only run when the starter button is pushed. The mag then reverts to its normal 20 to 25 degrees BTDC for running. These systems are too expensive for most automobile type folks though.

They used to use the impulse coupligs a lot but due to failures of these systems, most don't recommed there use anymore. All the impulse coupling did was delay the rotation of the mag about 15 to 20 degrees until the engine fired off and the flyweight pawls deactivate them at anything above cranking speed. The damn flyweights would fail and do damage to the mag, engine, or both so you can figure why they are trying to abandon these systems. They would work OK on an auto engine if you could rigg one up.

Some aircraft mags have a 1000-hour overhaul (or bearing replacement) and others will go the engine TBO for the most part(1500 to 2000-hours). We always keep spares on the shelf for when one croaks. Aircraft always have dual or twin systems so one will keep it running but the performance drops off and you can really tell when one goes. On a car it would just go to back firing and raising Caine or it would just quit altogether. If I was racing one, I'd figure on replacing it after a season and having it overhauled. This would include new bearings/soft parts and if the gaus is low in the magnet, a remagnetising would be in order. They take some maintenance but they work well.

Kerby
 
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Note on Advance: Most SBC Vertex mags come with mechanical advance plates for 12 degrees total in them - which is 24 degrees at the crankshaft. If you're going to use one of these in a flathead, you should consider one of two options:

a) Have the advance plates changed to 8 degree ones -- for 16 at the crank. Then you can set 4 - 8 degrees of initial timing and you'll have a perfect setup.

b) Have the mag 'locked down' - with no advance. Then you'll set the advance like Bubba said and leave it.

Note: You can't tell what advance plates are in it - or if it is locked down by grabbing the shaft - it needs to be taken apart to verify!

I think option 'a' is the better option and since you should probably have a used mag serviced anyway, have them change the advance plates at the same time.
 
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