Spark Plug Savy

[mdaspit]

Would someone explain the difference between
the NGK R8102A10 and a R7424A9, in a 302?

I think I understand that the 9 is a hotter plug than the 10, and that a hotter plug takes longer to transfere its heat to the head, but when/how do you know what temp plug to use?

Plus, what do the other numbers indicate?

[seanp3]

90% of the time I use the 10 heat range just because of the summer temperatures that we run in, and they're the easiest to get. However, in winter testing or races in early spring where temperatures are cooler I use the hotter plug....... either a heat range of 8 or 9. Bottom line...most of the time you can't go wrong using the heat range of 10.

[mdaspit]

Here is what a dealer told me after looking in his book to "Decode" the plug number.

R8102A10 = R stands for Resistor. (I assume this is needed because of electronic ignition in the 302)

The first number, 8 stands for the heat range.
The last number, 10 stands for the gap.
I'm not sure what the numbers in the middle stand for....

But, I'm out in the country, and these are some good ol boys, but this kind of stuff just may be above their pay grade.

[seanp3]

Go to sparkplugs.com and you should be able to find some info. For the 18mm plugs I think the NGK R8102A-10 is your only option. And it was my understanding the 10 at the end is the heat range. If you buy a used 14mm head you have a lot more flexibility with different heat ranges. If you have the 18mm head you won't go wrong using the NGK R8102A-10

[blueskyracer]

[

But, I'm out in the country, and these are some good ol boys, but this kind of stuff just may be above their pay grade.[/QUOTE]

I like it, kind of like the good old boys of Montana where sheep are nervous, ALWAYS!

[canoecty]

NGK plugs

R = resistor type plug; no symbol in front of the R should indicate an 18mm plug with a 12mm reach. The first number is the heat range. The lower the number the hotter the plug. I think the -10 indicates the container size (10 plugs in a box); at least that's what our boxes indicate.
You don't necessarily need a resistor type plug in a 302. We run B9ES plugs in our 302 mods with 14mm heads. I find them in our local NAPA store. Sparkplugs.com is also a good source for plugs and info.

Dave Curtis

[mdaspit]

Excellent. Thanks a lot guys, I appreciate it.

[johnsp]

Check out this pdf file, it will tell you all you need to know about the numbers.

http://www.ngksparkplugs.com/docs/te...tnumberkey.pdf

[Fast Freddie]

It's An NGK Racing Plug

R8102A10 is an 18 mm plug with a 16 mm reach and a 1" hex, non-resistor, gasket type, with a connector stud, and a flush side electrode. In the racing plug nomenclature, the final number is the heat range. In this case, a 10 (cold). The leading R is for RACING! Straight out of an NGK catalog. The 4-digit numbers between the R and the A are NGK's numbers, apparently some sort of engineering sequence and mean little.

Fred

[G Stillwill]

Heres a link to the racing plug charts.

http://www.ngk.com/sparkplug411.asp?...g+Chart&mfid=1

[Fast Jack]

Ngk

Ask your NAPA to get you a copy of the NGK non automotive catalog. There is a break down of the plug #s , its free!! The last - # indicates a pre set gap -10 = 1 mm.

[G Stillwill]

In the non racing plugs the last number is the gap as in BPZ8HS-15 the 15 is the gap 15=.060 and in the racing series plugs the last number is the heat range.