This started out with a phone conversation of a intermittant ignition system problem on a flathead. Seems as if the customer bought all the right parts ( or at least he thought he had) for the project he was working on. Mallory Breakerless distributor, Mallory # 29216 ignition coil , a Mallory external ballast resistor and a power cell. A quick ohm test shows the coil at .6 ohms and the ressitor at .7 ohms. WOW way to low for this system!!! A quick look thru the net at Summitt parts shows the # 29216 coil at .6 ohms and a note of NOT being compatible with high energy systems.. The correct coil would be the next one down # 29219 with a note of "designed for Mallory Breakerless Ignition" another deal gone bad !! I took the entire system , wired up to a 12 volt battery with a spark output load and ran on a test machine. Just what i thought the system is drawing approx 11 amps of current and got very hot very quickly!!! Another interesting issue is that when the unit loads up to 11 amps there is a internal spark jump from a black connection to the mounting screw and a very bad missfire !! ( shown in picture) Even if we get the correct coil i would never trust the controller after seeing it breakdown with a internal short!! The fix ? Beats me , i would just start all over i guess???
Thanks Bubba- I read everything you post. I don't always understand it, but I appreciate your experience and expertise.
Actually thats what i did , its not the way i wrote it on the towel. But 14 divided by 1.3 = 10.76 or 11 amps as stated......... Interesting that the ground screw jumps spark as the current ramps upward. With a meter on the amp flow the amps would run from 7 to 11 amps . When the amps got close to 11 amps the spark would jump to the screw like the picture shows. I think the current limiting in the module was kicking in and going to ground . In this case a open circuit to ground...????
I think i used that same coil with a unilite on a sbc. It ended up burning the center cap carbon thing and the rotor. I wasnt sure what caused it. I put the coil on eight years ago and only drove it like 5 thousand miles. Now its got a bubba dizzy and runs much better.
Yep thats the fix use a # 29219 coil ( right below the 29216 coil in the Summitt on line listing) it has a resistance of 1.4 ohms , add a 1.5 ohm resistor and things become more manageable. On this one the module jumping to ground is another issue. I think i can just lower the current ( correct parts) and seal the ground connedction ( GE Gyptal) and we will be ok...
Is this where it's arcing from? It looks like it may be the minus connection from the coil of the magnetic pickup. I'm thinking the high primary coil current is coupling to the mag pickup coil and generating the arc. It may not have affected the module and the Glyptal and if possible re route the wires out of the module so they are not so close to the pickup should fix it; along with the correct coil and resistor. If worse came to worse I bet you could replace the Mallory module with an HEI, but it doesn't look like it would fit inside the distributor.
Yes , and to make it more interesting i put a amp probe on the battery lead. The current would run from 6 to 11 amps. Everytime the current bumped to 11 the connection would arc with a snap and spark. My theory is "bubba logic" that the module has current limiting protection set at approx 10-11 amps . Problem being that a current limiting circuit has to do something with that excess current, either control the circuit by shutting it off/on etc , or putting some of the excess to ground... Ie: The early GM fuel injectors would short ( high amps) and the current limiting would take out a single cylinder ignition firing . So you had a car with a cylinder ignition missfire caused by a defective fuel injector. We are going to use gyptal and a new correct coil and resistor....news at 11!
Am confused here - Summit page for 29219 coil says coil has a resistor so separate one not needed and Mallory Instruction diagram for magnetic distributor and this coil does not have separate resistor - Post here says use that coil AND add a 1.5 resistor - Should a resistor be added to a coil that Mallory says already has one ??
The discussion was as to the problem with the Mallory module jumping spark causing a missfire and high current flow. These systems can be miss leading and often are based on the manufacture and then the cataloging of parts. The summitt , jegs etc catalogsd usually have the details of the part, and this may or may not be correct. The magnetic and uni lite Mallory series doesnt like to see over 8 amps . Yes the 29216 has a primary resistance of .6 and this is way too low to use on these units. The system likes the 29219 coil ( 1.5 ohms) but doesnt like the lower .6, just simply too much current. Might work for that short blast around time but a longer trip ( more heat) will wipe them out every time...
I've noticed that ignition parts catalogs are often wrong on whether or not a coil requires a ballast resistor. I've gotten one that the catalog says doesn't need one and on the coil body it says it needs to be used with a ballast resistor. We had coils stocked for forklifts because the operators would forget to shut off the key when they ran out of propane and if the points were closed and they left it on overnight, it would burn out the coil and weld the points together.
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