MG Sports Cars

Hoping to solve a problem I cant seem to get right. This is the second Pertronix Flame Thrower coil I have fried. Car has a Buick 215 bored 0.30 over, decked 0.10, using the original rebuilt distributor, with a pertronix Ignitor Electronic Ignition, Pertronix Flame Thrower 40,000 volt 1.5 Ohm coil, Accel 8mm plug wires and the plugs are gapped at 0.30. The two coils I have used both got quite hot and ultimately fried (see picture of the most recent one, not sure why it posts on its side but is correct if you click on it). The instructions for the ignitor say this is the one for 8 cylinders and to remove any ballasts in the system. The car is a garage queen even though it has been in running condition for some time now. It only has about two miles on it from going up and down the road testing various things. The engine may have 6-7 hours running time at this point (although I wasnt really keeping track). It has always been hard to re-start especially when hot and I suspect that is related to the coil. Having just fried a second coil it is clear that something isnt right. I noticed that Mike Shemp talked about the same problem back in 2009 and I am uncertain if he solved the issue. I should also note that I had the coil mounted on a 45 degree angle which I will correct when I get the next one. Any thoughts would be appreciated.

Hmm. My Flame-thrower coil has been mounted horizontal on the intake manifold for the last 20+ years without issue. It is the 1.5 ohm version with 12 volts going to it.

I do have the hard restart when when hot. I attribute it to heat soak.

Hi Richard.
Does your car sit with the ignition on and engine not running?
That is the leading cause of severe coil overheating like you are experiencing.
Possibly your ignition is live with the key in accy?
A low OHM coil like the flamethrower won't tolerate a full load like that for more than a few minutes.
I know that Pertronics says to remove it but. I would power the coil with a ballast resistor and live happily ever after.
Just remember to run full voltage to the module to keep it happy.

Live like you mean it.
Fred

I agree with Fred.
A 1.5 ohm coil should not be fed 12 volts.

Oil-filled coils, if that is what you have, are old hat nowadays.
A resin-filled coil, like this Flame Thrower, will happily mount any way up.
This one - sorry for the UK listing - is 3 ohm, which is correct for a 12 volt feed.

I will agree for an old school coil. The Pertronix coil was designed for 12 volts in certain applications.

As I said, mine has been wired to 12v for 20 years without issue.

From Pertronix:

"• Bypass resistance wire, connect a 12-gauge copper stranded wire from a 12-volt
switched ignition source to the postive (+) terminal of the coil."

All,
Thank you for the insights. I will go through and recheck everything.

Carl,
Sounds like you and I have the same setup but since I am frying my coils I must have wired something wrong.

Fred,
I dont leave it for long periods with the key on but a few minutes or more, I am sure I do. I have also run the switched wire through a cut off switch inside the car which I flip off when not working on the car (mostly a security precaution) so will re-check that to ensure I havent done something wrong there. Obviously it is getting too much electricity from somewhere and that may be the culprit.

Ivor,
I didnt realize non-oil filled coils were the better option. Definitely behind the times. Will switch to one of those.

Thanks all for the help

Just so we're all on the same page.
With the engine running, a 1.5 Ohm coil, on an eight cyl or more engine, never sees enough saturation to overheat.
With many aftermarket ignition systems the coil is not energized at rest, IE with the key on and the engine off.
The Pertronics module is different and it grounds the coil with the engine stopped.
This is not an unusual situation and many OEMs operate this way with a high current coil. However all of these systems employ a ballast strategy to reduce the current to the coil at rest.
The problem is not voltage related but rather current related. So as the coil is a voltage multiplier even with a ballast to reduce the current draw you still get one hell of a spark
If you are the "show me" type. (I am), hand someone your beer (or Scotchy Scotch) hook a low ohm high current coil up to a battery and walk away.
It only takes a few minutes for it to get exciting!

Cheers
Fred