Distributor/coil issue

[supertruck]

Running a Mel's distributor and coil for several years with few problems until the last race weekend this season. Engine developed a stumble/miss above 7000 RPMs. After trying all the obvious things - fuel, carb, timing, plugs, etc. - we switched the Mel's coil with a new Accel coil. The problem went away and the engine ran strong in practice and the race. Mel says not to use any other coil with his distributor, but since this is the 3rd coil in 4 seasons, I'm hesitant to shell out for another of his. Other than resistance, what are the things to look for in finding the coil that will work with the Mel's setup?

[car62]

id suggest checking the all grounds, maybe move the coil away from heat...no reason you should be losing coils all the time.

[supertruck]

Thanks but I believe I'm OK there. I mounted the coil on the front down tube of the roll cage, on the side opposite the header and about a foot outboard of the block and up level with the intake. I have a good ground from the engine to the frame, coming off the cover plate for the fuel pump and to a bolt welded to the frame. I also noticed that each time the coil started to give me that miss/stumble during a run, it was hot to the touch after pulling into the pits.

[Browndog]

Are you running an alternator? If you are maybe check the voltage to the coil when it is running with the rpm up. Might be too high.

[supertruck]

Thanks but I'm not running an alternator. I am running two batteries in series to keep the voltage up during the race. What voltage is considered too high?

[car62]

for any part of the ignition system anything over 15 volts is too high

[Jb35]

Im thinking if you have 2 12 volt batteries wired in series thats 24 volts. You would want them wired parallel. Correct me if im wrong.

[Browndog]

Yes that is right. If you are in series then you are 24 volts which will wipe out a coil for sure. Why 2 batteries? Are you using them for ballast?

[supertruck]

My mistake on that, they are wired parallel, getting 13 volts. I run 2 batteries for (1) minimizing voltage drop during the races and (2) adding weight to the left side without using an extra bar of lead. I run an S10 with the Ford engine.

[dave41]

fuel pump plate with gasket underneath in not a good ground .don't put just one ground. put as many as you can

[supertruck]

Thanks Dave

[Old Rob]

How are you mounting the coil. It should be standing up as much as possible. Never mount the output pointing down as that will draw the oil away from the coil windings, which will make it hot.

[supertruck]

The coil is mounted vertically and the coil wire is the standard one Mel supplies with his kits. Still not sure why I'm burning through his coils and would prefer to go with another brand if I can find one that is compatible with his distributor/internal module. I know he uses Pertronix electronics, but they won't tell me if their coils will work - they say it's proprietary info.

[7uptruckracer]

How is your wiring run to the ignition, and from the distributor to the coil? Does your tach ever read funny? Is your coil insulated in the mount, is the mount insulated between that and the frame? Yes this is Brad lol We fought a similar issue earlier in the year.

[supertruck]

Hey Brad - we may not have to worry about it if Langley falls apart, right? Wiring from the coil to the distributor is straight Mels stuff as supplied by him. From the ignition to the coil is straightforward, nothing funny there - same as my previous truck and we never had a problem. The coil is mounted with a standard coil mount like you buy at the auto parts store, no insulation. I never heard of insulating the coil/mount from the frame. I'm thinking there's an issue with Mels coils but I've been wrong before. Would be nice to find a substitute coil so I could try it. But no one can tell me how to compare coils. I figured it would be by measuring resistance and making sure they match but don't know if that's the way to go or not.