Spark plug heat ranges

[82BBC20]

I’m trying to understand spark plug heat ranges, I know the ac delco heat ranges starting at 41 going up get hotter, what I don’t understand is I see ac delco iridium plugs and others listed on summit with heat ranges of 16 +/- ! How do these heat ranges compare to the 41-46 heat ranges with 46 being the hotter plug. I’m confused! Btw I’m running a 454 with all forged internals, roller cam, Edelbrock rpm performer aluminum heads.

 

[Grit dog]

You just need to research what the heat range is for the brand of plug you’re looking at. Not all are higher number = hotter.
For example NGK is higher number = cooler.

But I don’t believe there is a standard for comparing actual heat ranges if that was your question.
Without measuring cylinder temps, which is dialing in an engine more than just a nice rod driver motor or adding obvious massive heat like supercharging or really high compression, I wouldn’t think a big block would be that finicky. If they’re too cold and fouling that’s one thing, otherwise I’d just run a mid heat range and call it good.

 

[fast 99]

and don't buy all the hype spending more on magic plugs that will "make" HP. Plain old AC or Champion will be just fine. One reason for Iridium or other exotic plugs is the extended change interval. Some are 100k.

 

[82BBC20]

I guess what was confusing me the most was seeing ac delco plugs with standard 41-46 heat ranges then seeing ac delco iridium plugs with heat ranges at 16. But gonna stick with regular ac delco with a higher heat range, thanks for the help!

 

[Grit dog]

and don't buy all the hype spending more on magic plugs that will "make" HP. Plain old AC or Champion will be just fine. One reason for Iridium or other exotic plugs is the extended change interval. Some are 100k.

100%

 

[Grit dog]

I guess what was confusing me the most was seeing ac delco plugs with standard 41-46 heat ranges then seeing ac delco iridium plugs with heat ranges at 16. But gonna stick with regular ac delco with a higher heat range, thanks for the help!

Generally I think the more power you make, relatively speaking, generally the cooler the plug you want to run. Again I don’t think a regular R44T whatever is 20+ heat ranges hotter.

 

[Rusty Nail]

Oh no!
I don't wanna dip my toe in --
i'm gonna cannonball!

Maybe somebody else can help elaborate. I may have forgotten some things about it but I THINK, MAYBE that "heat range" of a sparkplug has very little to do with the temperature it can generate. Heat range is indicative of the spark's duration across degrees of -cam timing. How long it actually fires after receiving signal from the distributor.

Tune this with engine rpm to make power or to - adjust the powerband .

Oy vey!

Ready? Go!

 

[Rusty Nail]

If you want good advice about what spark plug to run OP, ask your camshaft manufacturer for a recommendation .

 

[WFO]

I wouldn't run Champion plugs if they were giving them away.
The only thing that made them popular was advertising.

 

[Ricko1966]

I guess what was confusing me the most was seeing ac delco plugs with standard 41-46 heat ranges then seeing ac delco iridium plugs with heat ranges at 16. But gonna stick with regular ac delco with a higher heat range, thanks for the help!

You don't want a higher heat range unless you're having a problem with the range you are running. Hotter doesn't gain you anything except preventing fouling. But it adds another Hotspot for preignition,more heat for more chances of cracks at the plug seat and more heat means a less dense air fuel charge. On a performance application I run the coldest plug I can get away with without fouling

 

[fast 99]

Plugs that are too hot will erode the electrodes much faster. AC doesn't have many different heat ranges. We run CR43 [wider electrodes] in HD trucks [2 tons] and mostly 44 or 45 in light truck and passenger applications. I omitted the suffix T or TS to simplify. If you don't know what is correct 43 or 44 should be safe to start.

Cross-reference catalogs aren't always dependable.

Other good brands are NGK and Autolight.

 

[bucket]

The Edelbrock cylinder heads probably came with instructions and the instructions probably list a recommended spark plug. That's where I'd start.

 

[Turbo4whl]

Mechanics of a spark plug heat range; On a hotter plug the glass insulator is longer around the positive electrode. What this looks like on a cold plug, the angle of the glass insulator is wider so the insulator contacts the the negative side near the tip. On the hot plug the the angle of the insulator is narrow and contacts the negative housing of the plug much deeper.

Also on most brands, the positive contact is a smaller in diameter on the hot plug, than the cold plug. As stated above, run the colder plugs, they will last longer so long as they don't foul.

This info will help to understanding heat ranges on different brand plugs, with different numbers.

 

[Grit dog]

^what he said.
There’s some confusion in this thread. Has really nothing to do with timing or cam duration and everything to do with heat dissipation.
Easist way to understand what @Turbo4whl said is to look it up. The majority of the heat dissipation is through the plug body at the threads in contact w the head. And the rest of the exposed steel portion like where the wrench goes.

 

[82BBC20]

Yes I’m having a problem with fouling plugs, have been running stock heat range of 41 but upgraded the distributor to a Davis Unified that recommends wider gap on the plugs so now I’m fouling stock heat range plugs. Will increase heat range to get where I need to be, I appreciate all the help!