69FECoupe

Did you order the 6V coil or the 12V coil. If you ordered the 12V model and connected it to the stock power (resistor) wire, the coil will not operate correctly and will make a weak spark.The stock coil is a 6V unit. Those platinum plugs need more juice than regular plugs so if the spark is weak they may not fire.

morg68stang

That makes sense. I didn't change anything when I put the new coil on. What are my options? Rewire the coil? Go back to a stock coil?

69FECoupe

If it were mine, I'd put the stock coil back on and as somebody else suggested, can the platinum plugs. If you want to keep the Flamethrower coil, you'll have to bypass the resistor wire to ge a full 12V to it. I'm pretty sure Glen has something posted about this subject in the FAQ section. You might want to check it out.

morg68stang

Well, I replaced the coil back to what it's supposed to be and replaced the platinums with copper plugs. Runs like a charm now. I guess I'll have to jump on the Platinum sucks bandwagon because I left them in after replacing the coil and it still ran like crap. The copper plugs did the trick, though. Of course, it cold have been that they were fouled out from the attempts to getting it running correctly before. They were awfully black when I pulled them out.

Anyway, new problem. When I turn on the fan to my heater to make it blow air throug the vents, the engine starts running rough and dies. You can rev up the engine to a little higher RPM and turn it on and it still starts to stumble. Does that sound like a weak battery?

SuperHoss

Well, if it's the plugs then there's nothing I can say...I've always had good luck with the platinums though.

Colorado_Mustang

Couldn't be more wrong, here.

HEI ignitions have a more powerful spark and vaporize more of the plug with each firing. How long the plug lasts depends on how much material is removed from each spark. This is why platinum and other dense material plugs last longer than copper, there are more atoms to be vaporized. And, don't try to run 100k on a set of plugs no matter what your service life says. If the gap gets too wide, the coil will need to put out more voltage to jump the gap, which accelerates the wear process and heats the coil. As this escalates, the coil(s) and plugs will eventually fail 100%.
I've never had luck with platinum plugs unless they are OE items. I ran Bosch platinums, Split fires, Accel U-grooves, and a set of those surface gap plugs at one time or other in my '71's 302 (dual point Accel dizzy with Accel Super Coil at the time). The Split-Fires melted within 300 miles, the platinums never ran correctly, the U-grooves melted, and the surface gap plugs were worse than platinum. Coppers have worked the best, and last a couple thousand miles (at best)...which is a year, maybe two.

SuperHoss

Then do you care to explain to me why plugs in a carbureted engine need to be changed more frequently than plugs in an engine with EFI and a computerized firing system. Most systems are not HEI anymore, I'm not even running one...

I've never tried to run a set of platinums longer than a year in my car...that's about how long the Autolites will last (I only got about 6 months out of the Bosh Platinums before they failed). I've had good luck with the platinums.

Colorado_Mustang

It has more to do with the tune of the engine and that most carb'd engines were fired by points, which are very low energy. These two items will carbon foul the plugs quickly...a problem a fuel injected car with HEI won't have (unless it's worn, of course).

Many old timers would simply clean and regap spark plugs and put them back in. This could be done a couple times before needing replacement.

rmodel65

just go standard motorcraft plugs ive had several car that had the original plugs and when i pulled them look almost new, one was 24yrs old and the other was 28yrs old had the original plugs and wires that were date coded always go oem unless ur racing