A recent post on spark plugs got me to thinking about my own truck. It occurred to me that I may not want to use stock Motorcraft ASF-42 spark plugs in my 1985 302 since I will be running an HEI ignition. Anybody else out there running HEI?

Guess I could run plugs intended for a Chevy HEI application.

I'm also thinking I should run a .045 to .060 gap.

Any constructive comments?

 

I don't think the stock plugs will work I made the mistake of putting reg motorcraft plugs in when I changed mine with a dura-spark system it took me a while to figure out why it was popping & stalling when I pressed the accelerator. When I put the old plugs back in it ran fine.

 

Makes sense. Since they fit into the same hole I'm seriously thinking about using a GM HEI application plug...

 

Guys, Ford's Duraspark ignition is HEI. That just happens to be the name GM uses for their electronic ignition. And Ford has been using electronic ignition in their cars since 1975. (Actually, back to the early 60's, but that's another story) The stock plug will work fine for any electronic ignition application, even super duty and racing stuff like MSD.

Lots of plugs may 'fit in the hole,' but what really matters is things like depth of reach, electrode length, seal type, etc. (I'm not going to get into heat ranges) That's why it's important to know what year the heads are to get plugs that fit correctly.

 

You can safely bump the gap up a little (not a huge gain in any respect) but Wayne is right, the plugs don't know where the spark is coming from. Use stock.