No, there really is nothing you can check on a mag spinning on a running motor that will do you much good. The mag must be set up a specific way and spun up on a machine with test equipment connected to really see anything useful. If you have spark and the timing is staying put, that's about the extent of "on the car" testing that can be done.
The magnets lose their energy slowly with use -- they don't get any weaker from sitting on the shelf or on a motor that isn't running. If you get 50 passes or less per year on your car or the motor is spinning less than a few hours total (circle track), you're probably fine to send it in every other season. If you are putting many laps on your car, consider an annual service the minimum. If you lap the thing every week and find that the ignition gets weak plan on more regular service or consider investing in rare earth magnets that don't need recharging. Be aware that mags do not like moisture and will rust and corrode at an alarming rate! Part of sending your mag in annually is to make sure everything is healthy. If you plan to only do this every other year, be sure to pull the mag and keep it warm and dry. Leaving it in a damp, humid trailer can do damage to the mag and will leave you with problems.
The magnets in a mag never go completely dead. They lose energy slowly with use after a charge until they reach a certain point and then they stabilize. It is more likely that the coil has failed, the points are severely fouled, or there is a short somewhere. A magnet never gets so weak that it won't spark at all unless the plug gap is huge (more than .020") or the magnet has been de-magnetized. Welding on your car without first removing the mag is supposedly one way to do this.
It depends on the application. Most drag race motors seem to do fine with a locked out mag that contains no centrifugal advance. Many high compression gasoline engines however kick and buck against the starter. Employing some kind of advance mechanism allows the static ignition timing while cranking to be much lower allowing it to start easier. Once the motor is started, the advance can be set up to come in quickly so that it's "all in" early. When used in this way, it really is more of a "start assist" than anything else. In street applications, some centrifugal advance can really help power and prevent detonation. The advance mechanisms can become sticky and corroded over time however. Mags that have not seen service in a while can become "locked out" on their own as the mechanism gums up and quits moving freely.
By running a tight plug gap, you are making sure that the spark gets to the plug. If you run a wider gap than that with a mag, you may end up with the spark arcing to other objects inside the mag or crossfire between plug wires. The spark plug needs to be an easy path or it will find another.
No one really knows for sure what you'll require, but we can make some educated guesses based on the experiences of others and their equipment. Here are some general rules of thumb that will ensure good performance...
Circle track: Standard OAC Vertex or Sprint Mag (up to 2.5 amps)
Street/Hot Rod: Any standard OAC Vertex or Sprint mag
Blown gas: 2-3 amp Vertex or Super Mag 2
Mild Blown alcohol (up to 10 PSI of boost): 3 amp Vertex or Super Mag 3
Moderate Blown Alcohol (up to 20 PSI boost): 4 amp Vertex or Super Mag 4
Hard core Blown alcohol (~30 PSI boost): 6 amp OXC Vertex or 6 amp Super Mag 5
Injected Nitro (50%): 4 amp Vertex or Super Mag 4
Injected nitro (up to 100%): 6 amp OXC Vertex or 6 amp Super Mag 5
Blown nitro: 7-8 amp Super Mag 5
There are pros and cons to each (points vs. electronic). Basically, all the cons of the MSD electronic Pro Mags are not an issue if money is no object.
First of all, don't let the advertised "amperage" numbers fool you into thinking that the electronic mags are vastly superior in output. A hot Super Mag 4 is pretty much equivalent to an MSD 12 Pro Mag at the spark plug (voltage and current). An 8 amp Super Mag 5 is pretty much the same as an MSD Pro Mag 20. The two styles of magnetos are totally different and the primary amperage generated means NOTHING when comparing output..."apples and oranges". There is nothing with points that compares in output to the MSD Pro Mag 44. Unless you're running Top Fuel, a Pro Mag 44 is probably expensive overkill.
Magnetos with contact points
Pros:
+ Smaller initial investment
+ Lower cost of ownership (parts, service, etc.)
+ Less $ in spare parts required in the trailer
+ Easily field serviceable
+ Good, used units available/plentiful
Cons:
- Points eventually wear out
- Rev limiters and timing retards difficult to integrate
Electronic magnetos
Pros:
+ No points to wear out
+ Rev limiters and timing retards are easily added
Cons:
- Larger initial investment
- Higher total cost of ownership
- Shortage of used units and spare parts (must buy new)
- Not field serviceable (spare electronics box needed)
- Can be harder starting than a points style mag of similar output
No, those shops might tell you that the paint keeps the screws tight, but there really isn't a problem with screws coming loose in a magneto. It serves other purposes, none that we at FIE feel are warranted. The biggest reason for the paint is to cover up the color used by the last shop and make it look like they did something. Most places do not tear the mag completely down like we do. Since we clean everything and use all new hardware, we don't need to cover up anybody's red paint with our yellow paint. We don't need to do that to make it look like we did something, usually it is obvious by the clean, gleaming parts and new stainless screws everywhere.
Another purpose of the paint is to signify to them that a particular screw has been tightened. We keep track of this and don't need the paint to remind us of which screws we've torqued.
Yet another is to let them know if you've tampered with the mag or not. If you have problems and send it back to them, they want to be sure you didn't open something up, mess with it and blame them. We trust you.
The heat, ozone and wind present inside a magneto causes the "nail polish" to flake off and can in itself cause problems. Paint dust and chips in the points are not desirable!
We do use white, non-corrosive silicone only on places where wire terminations are screwed to fixed attachment points. The vibration of the wires can indeed cause these screws to loosen. The silicone insulates, absorbs the vibration and keeps the terminal joint clean and corrosion free. We are careful to use special electrical grade silicone that does not emit acetic acid as it cures. Regular silicone gives off acidic fumes that corrode metals (including contact points!).
There are three transformers (coils) currently available from Mallory for magnetos. The red-topped #28900A (lower left) is for Sprint Mags and Super Mags up to 4.5 amps primary. The black-topped "nitro coil" #28990 (lower right) is for hotter mags between 4.5-6.5 amps. Finally, the #28901 Monster Red coil (rear center) is for anything over 6.5 amps. These transformers can be used with OXC Vertex magnetos just fine as long as they are properly matched to the output.
The red-topped 28900A should never be used with a mag that powerful. The 28990 isn't good either. The reason is because the winding "turns ratio" inside the coil is matched to a particular range of output. When a hot mag is pumped through the wrong coil, the spark duration ends up very long. You might think this would be good, but it isn't at all. Even with the large diameter pro cap, the spark lasts so long, that it can jump to the wrong terminal in the cap. There isn't sufficient "off-time" to ensure that the spark goes to the cylinder it should. Cross-firing in the cap and missing and sputtering under a load are the symptoms. You might also see scorched or melted rotor contacts.
You can, but it won't really gain you much. Current at the plug will be greater, but voltage is what makes the spark jump the gap. The consequence of using a smaller mag than a coil wants is that the motor may be hard to start. It might require a faster cranking speed to make enough spark to start the motor at all.
Heat! There is a special rotor you need to use to prevent problems with Super Mags over 7 amps. The brass blade is larger and makes a circular loop around the center of the rotor. This makes it able to dissipate more heat. Also, the screw is epoxied in place so that it won't come loose...ever! Some folks think they can put loctite on the screw of the regular rotor and make that work. Heat causes loctite to loosen! The brass blade will come loose while the motor is running and can cause major damage to the mag and /or the motor. When in doubt, put the high-temp brown rotor on it. They aren't that much more money.
Most people doing this have clearance problems with blowers or firewalls and don't have room for the big pro cap. You can get away with it on mags under 4.5 amps if everything is kept in top shape. If the cap contacts are clean, the inside of the mag is kept oil free, the plug wires are in good shape, plug gaps on the small side, etc. If anything at all is marginal, misfiring and problems can result.
The big yellow things are capacitors or giant condensers. These prevent the points from arcing - that's all they do. These are like electrical buckets that give the current someplace to go for a brief instant as the points are opening. The more current, the bigger the bucket needs to be. The more output the mag makes on the primary side, the more capacitance it needs to keep from cooking the points. The standard capacitors are:
Combinations of the 1.0 and 1.6 capacitors can be used up to 7.5-8.3 amps (twin 1.6uF capacitors). So, the more capacitors you see, the more powerful the mag, but the capacitors don't make power. Putting too much capacitor on a mag (or "overcapping") sucks the life out of things and hurts the rise-time of the spark.
The Super Mag 2 and 3 are identical except that the magnet in the Super Mag 3 is stronger at 3.8 amps over the typical 3.3 of the SM2. The Super Mag 3 has a long, metal .56uF capacitor on the outside, while the Super Mag 2 has a smaller .36uF on the inside. Both the 2 and 3 need to be recharged periodically.
The Super Mag 4 contains the same windings internally as the 2 and 3 but has a more powerful "rare earth" or neodymium magnet that makes approximately 4.2 amps and never needs recharging. It has the same long metal cased .56uF capacitor as the Super Mag 3.
The Super Mag 5 has a different winding on the inside that changes the output drastically. They usually contain a rare earth magnet, but some have undergone a winding upgrade but kept the existing Super Mag 2 or 3 magnet. The output of the Super Mag 5 varies with magnet strength and can be setup to output anywhere from 5 to 8.3 amps primary and utilize a variety of capacitors on the outside. The Super Mag 5 should be fitted with a 3-wire harness. The extra ground provided in the 3-wire harness should be run to the engine block or cylinder heads.
Yes, a few. They generate so much output, that they demand more attention than a lower output mag. Nothing can be marginal. Replace plug wires every year, the coil wire a couple of times per season, caps and points every season (or more often). You can't ignore it and expect it to run forever. Also, unless you can spin your motor over fairly fast when starting, you may have difficulty getting reliable starts. The motor needs to spin 250+ RPM to start reliably. A blower-snout starter probably won't have any problem doing this, but some stock-style, engine mounted starters may not cut it. Also, the large diameter pro cap required and the two big yellow capacitors on the outside can cause clearance problems with blowers and firewalls.
Yes, the Mallory transformers are oil filled and the high-tension terminal must be at the lowest point (covered with oil internally) or they can fail. The best position is with the small primary terminals UP and the high-tension lead low and aimed out the side. The next best is with the high-tension terminal pointed straight down. The WORST is with the secondary terminal pointed straight UP.
Sure! The Sprint Mags are pretty much comparable to a Vertex in that they are a lower output mag that can be run continuously for circle track, street, etc. They utilize an external coil and make from 1.5 to 2.5 amps depending on the model. Many (but not all) of the parts on the Sprint Mag are interchangeable with the Super Mag.
Take a pass. The electronic Super Mags have been discontinued by Mallory and most of the parts for them are no longer available. These units were not very reliable. Back when they were new (in the 80's), the power transistors used in them were not very robust compared to today's standards. The high output of these units meant that they continuously ate themselves alive and needed constant maintenance. If it's for sale cheap, it probably doesn't work and the parts are probably hard to find or not available...or they'd still be using it instead of selling it!
With EXTENSIVE machine work to the housing and magnet assembly it is possible but expensive. It isn't worth it unless you're a machinist and want to turn the mag into a hobby. Most of the pieces in the electronic Super series are not compatible with the other Super Mags. It would be much cheaper to buy an old Super Mag 2 or 3 and upgrade it to an 8 amp mag than convert an electronic unit to points.
Remove the rotor and look at the rotor drive plate. Aim the plate so that it is pointing up and down (12 and 6 o'clock). Now look for the dowel pins in the drive plate that locate the rotor. If the dowel pin on the 12 o'clock portion of the plate is on the right side, it is right hand rotation (clockwise as viewed from the top - Chevy and the like). If the dowel is in the left side, it's set up for left hand rotation.
Don't loosen the point plate screws thinking you can rotate it enough to compensate and make it work turning the other way. There is not enough adjustment and the points will be totally out of phase with the magnet and windings. The result will be no spark at all. Send it in and have the rotation changed.
The Vertex OAC mags are a self-contained unit with the coil mounted internally. All it needs is a ground wire hooked to the terminal on the side for a kill switch. The OXC utilizes an externally mounted coil and is typically employed in high output applications (above 3 amps). The reason is that the Vertex is a very small package that gets very hot. OAC units making more than 3 amps can suffer internal coil failures due to the high temperatures created inside. The OXC moves the vulnerable coil out of the hot mag body. The OXC usually also uses one of two larger caps available (big and bigger) and the secondary coil lead enters through the center terminal. The OAC generally uses the small cap with the internal coil feeding the rotor up through a passage in the side of the cap.
OAC= Internal coil
OXC= External coil
Yes, a terminal can be added to the top of the old fashioned small cap that allows the external coil to enter. It is not recommended to do this with mags over 4 amps however, as the voltage can easily jump around inside the very small cap and cause problems. In situations over 4 amps, you really must use one of the larger caps.
A stock Vertex style mag makes about 1.5 amps primary with freshly charged magnets. After a good deal of use, the output can drop as low at 1 amp. Even fully charged, the Vertex is not as powerful as most other mags out there. BUT...this allows it to be used in sustained applications such as circle track, aircraft, boat and street use. The lower powered nature of the mag means it creates less heat and it can run continuously. The hotter mags (3+ amps) are only for shorter duration use (drag racing, etc.).
The stock vertex can be upgraded with more powerful rare earth magnets and a higher output internal coil to make 2.5-3.5 amps without a problem. If more output is needed than that, the mag should be converted to an OXC (external coil) unit to ensure dependability.
Remove the rotor and look at the top of the point cam. You will see an R or an L stamped into it. This is the intended rotation as viewed from the BOTTOM of the mag. An "L" means it rotates counterclockwise as viewed from the BOTTOM (or clockwise as viewed from the top). In other words, "L" means CHEVY rotation.
The only way to really tell is to take it apart and see if there is a advance weight mechanism in it or not. Even if it has an advance mech, it may be stuck and not working properly. The best way is to check it on a machine and see the actual advance or watch with a timing light as you rev your motor slowly. You can't tell by twisting.