Spark Plug Gap

[CornDog]

This may seem basic but I'll ask it anyways. I've always wondered, when should you open or close the gap on your plugs. I know the specs are usually good to set the gap at but if I could make it a little better, I would like to. Thanks

Justin
"CornDog"

 

[Cranky]

What ignition do you have? Stock points, electronic, aftermarket.....

 

[CornDog]

360 with Mopar electronic ignition kit (w/ orange box)

 

[Cranky]

Recommended is .035 unless that info has changed since the last time I messed with the Mopar EI systems. With the old points systems, it was common to set plug gap a little tighter to make it a bit easier for the spark to jump but with the better EI system, that isn't done anymore and I even set my gaps a bit on the bigger side....

 

[CornDog]

So if I were to install a Accell super coil or MSD coil, should I open the gap up a little? Thanks for your help.

Justin
"CornDog"

 

[Jonnyuma]

If you ditch that ECU and use an HEI module you can open em up to .45 or more.

 

[67 B-body]

The reason you see such a variety of plug gaps from yesteryears engines and todays engines, is primarily due to the fuel mixture. Todays engines run leaner with electronicaly controlled fuel injection and require a much larger gap.
If I were to put electronic fuel injection on my 440, I would open up the plug gaps then too. But with our older carb engines, I would go to .035" just like Cranky said.

 

[67 B-body]

One more thing,,,, If you have or know anyone with an engine scope, you can play with your gaps to get around 37kv.... That would be the best way of tunning in your plug gaps based on fuel mixture!

 

[Cranky]

If you ditch that ECU and use an HEI module you can open em up to .45 or more.

I tried that with the Mopar unit and didn't notice any difference on the track or for gas mileage in my race or street cars. I even did that stuff when ALL my cars were point systems in the dark days (I don't mind working with point systems!) but I did learn how to prolong my points systems tuneup! Even MSD units didn't really make anything run faster but they did seem to keep em running good longer. I did run a Mopar chrome box system on a 10.60 car and ran 7300 with it.....and it was supposed to be good for 7500? The only thing I don't like about the Mopar stuff is when the damn epoxy glue decides to run all over everywhere!

 

[CornDog]

I tried that with the Mopar unit and didn't notice any difference on the track or for gas mileage in my race or street cars. I even did that stuff when ALL my cars were point systems in the dark days (I don't mind working with point systems!) but I did learn how to prolong my points systems tuneup! Even MSD units didn't really make anything run faster but they did seem to keep em running good longer. I did run a Mopar chrome box system on a 10.60 car and ran 7300 with it.....and it was supposed to be good for 7500? The only thing I don't like about the Mopar stuff is when the damn epoxy glue decides to run all over everywhere!

I hate that nasty stuff!!! The ECU box can still be working just fine and the Goo will run out and make the biggest mess.

Thanks for all of the info guys. I'll probably just run mine at .035ish and I guess it'll be fine.

Justin
"CornDog"

 

[scotts74birds]

That just happened to me on my Harley this summer, caught in traffic. The timing was controlled by an optical sensor and the module above it released the goo and fouled the light sending unit!