Spark plugs for 302? what heat range are you running?
FTE Legend
Joined: Nov 2015
Posts: 30,915
Likes: 4,123
From: Angier, NC
Would need a little more information of why you run that heat range.
Like is the motor bone stock with 200K never been worked on other than oil changes and goes thru 1qt every 1000 miles and no leaks.
Bone stock and been rebuilt with 50K on it.
Some what built up, higher compression, larger cam, intake & carb but nice street driven truck.
Really built up 13:1 compression, more of a race truck than street.
Or does the motor have a blower / supper charger, turbo?
Each of the above would need a different heat range plug so you can't say "I used XX plug what you use'?
Dave ----
Like is the motor bone stock with 200K never been worked on other than oil changes and goes thru 1qt every 1000 miles and no leaks.
Bone stock and been rebuilt with 50K on it.
Some what built up, higher compression, larger cam, intake & carb but nice street driven truck.
Really built up 13:1 compression, more of a race truck than street.
Or does the motor have a blower / supper charger, turbo?
Each of the above would need a different heat range plug so you can't say "I used XX plug what you use'?
Dave ----
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Elder User
Joined: Jun 2015
Posts: 664
Likes: 2
From: York Pa.
Would need a little more information of why you run that heat range.
Like is the motor bone stock with 200K never been worked on other than oil changes and goes thru 1qt every 1000 miles and no leaks.
Bone stock and been rebuilt with 50K on it.
Some what built up, higher compression, larger cam, intake & carb but nice street driven truck.
Really built up 13:1 compression, more of a race truck than street.
Or does the motor have a blower / supper charger, turbo?
Each of the above would need a different heat range plug so you can't say "I used XX plug what you use'?
Dave ----
Like is the motor bone stock with 200K never been worked on other than oil changes and goes thru 1qt every 1000 miles and no leaks.
Bone stock and been rebuilt with 50K on it.
Some what built up, higher compression, larger cam, intake & carb but nice street driven truck.
Really built up 13:1 compression, more of a race truck than street.
Or does the motor have a blower / supper charger, turbo?
Each of the above would need a different heat range plug so you can't say "I used XX plug what you use'?
Dave ----
Post Fiend
Joined: Apr 2002
Posts: 19,311
Likes: 97
From: Waterloo, Iowa
When I was looking into this, the general rules are to first use the stock heat range or OEM plug to find a baseline.
The carburetor jetting and power circuits have to be straight first, and the ignition timing. Get that out of the way before heat range. Running more advance than stock needs a colder plug. If running lean at cruise for best mileage that will cause the plug to run hot. Racing and performance engines use really cold plugs, but they will foul up driving around town. If you do a lot of highway cruise, a step colder helps.
Another thing to watch, is the cross-reference charts between brands at least are kind of screwy. They'll try to tell you that one plug is the same as three or four different heat ranges from another. BS. BF-32 Autolites are hard to find now, at least at $2 anymore. They'll tell you Autolite 45 is the same. Nope, it's hotter.
One strategy that makes sense is to start with the coldest plug under consideration. Then work your way back up heat range wise. Can't hurt anything that way, the worst that will happen is they will foul, but if you run too hot of a plug you can cause permanent engine damage by holing a piston.
The carburetor jetting and power circuits have to be straight first, and the ignition timing. Get that out of the way before heat range. Running more advance than stock needs a colder plug. If running lean at cruise for best mileage that will cause the plug to run hot. Racing and performance engines use really cold plugs, but they will foul up driving around town. If you do a lot of highway cruise, a step colder helps.
Another thing to watch, is the cross-reference charts between brands at least are kind of screwy. They'll try to tell you that one plug is the same as three or four different heat ranges from another. BS. BF-32 Autolites are hard to find now, at least at $2 anymore. They'll tell you Autolite 45 is the same. Nope, it's hotter.
One strategy that makes sense is to start with the coldest plug under consideration. Then work your way back up heat range wise. Can't hurt anything that way, the worst that will happen is they will foul, but if you run too hot of a plug you can cause permanent engine damage by holing a piston.
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Elder User
Joined: Jun 2015
Posts: 664
Likes: 2
From: York Pa.
I was out running it pretty hard, pulled it into the garage, revved it a few times and turned it off.
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Post Fiend
Joined: Apr 2002
Posts: 19,311
Likes: 97
From: Waterloo, Iowa
Ya, me too. I first installed "hot" plugs years ago, because the jetting and ignition timing was off so bad, the plugs were fouling. It didn't help.
When you've got jetting and power circuits dialed in, ignition curve where you want it with stock plugs, then start looking at heat range. Start with a cold plug and work up. The ground strap will have a color change halfway when they are dead on. Too hot of a plug can cause pre-ignition, hotter plugs are only generally needed if idling a lot, like taxi or police service.
When you've got jetting and power circuits dialed in, ignition curve where you want it with stock plugs, then start looking at heat range. Start with a cold plug and work up. The ground strap will have a color change halfway when they are dead on. Too hot of a plug can cause pre-ignition, hotter plugs are only generally needed if idling a lot, like taxi or police service.
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