Spark Plugs RN12Y or RN14Y?

[Dave _S]

Last year I replaced my plugs with RN14Y's, because that's what the Haynes manual reccomends and it is also what the parts computer at Kragen recommended. Later, I acquired a '77 Jeep TSM and an original '77 owners manual. The Jeep refernces both say to use RN12Y's. The 12's are one heat range colder than the '14s I believe. So which is better the '14s or the 12's. I suppose the hotter plug may work a little better in older engines that use some oil, but what's the tradeoff? I expect Jeep specified RN12's for a reason. Any thoughts?

Dave

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1977 WT Cherokee, 401V8, TH400, PT Quadra-trac.

[Kenall]

the 12s are for when u do most of ur driveing on the freeway or at speeds above 60 for a long period of time. the 14s are for when u do mostly stop n go, short distance driveing and the engine does not fully warm up.

perhaps the 14 range was not avail when the TSM came out and only the 12s were being manufactured...

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Ken
1966 Super Wagoneer (http://www.home.earthlink.net/~kenns9/)
'The Predecessor'

[nograin]

I'ld go with the TSM and the owners manual. The others might have mixed up motors/models who knows.

If I remember right, every standard Mopar engine since at least the mid 60's has used RN12Ys, although its been awhile since I've had a slant 6 so I could be wrong there. Some of the Hi-Po motors like the 340 used the 9s, one step colder, as the recommended plug.

If you don't foul on the 12s, then use them. That is, look for carbon build up on them when you take them out. I think JeepBob had trouble getting 12s for some reason. I checked with my locals, and they are still available. I had a hassle from the chain stores over the 9s though.

The chain stores usually don't have a real parts guy (gal), and as the 4 pack boxes don't have the plug numbers on them, those guys are at a loss when you tell 'em what you want. So they try to look up the box number by the vehicle. Just tell 'em you have '57 Ford with '63 Cadillac motor with twin turbos and nitrous on a Jeep chassis, and a/c http://www.ifsja.org/ubb/biggrin.gif

On the subject. One local stopped carrying Champion to cut his misc. stock. Only Autolite. They used to be a good plug too. I don't know now. They were bought by Allied-Signal, same as Fram Filters, and I have read numerous times how bad the quality control is there. I have no idea if the HP line of filters is better than the regular. I'm looking for a new high flow oil filter brand for my race motor. To much marketing hype and not enoguh independent tests out there. IMHO.

[Slippery]

<BLOCKQUOTE>quote:</font><HR>Originally posted by nograin:
I'm looking for a new high flow oil filter brand for my race motor. To much marketing hype and not enoguh independent tests out there. IMHO.<HR></BLOCKQUOTE>

Try this one:
http://members.nbci.com/minimopar/oilfilterstudy.html



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Jason K.
http://us.f1.yahoofs.com/users/e46e6dee/bc/My+Photos/Festiva.jpg?bcw0GX7Ax3rIxilV
'88 Ford Festiva
40mpg work car
Cost $150, paid for itself already
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'90 Chevy Lumina
Biggest POS in the 115-year history of the automobile
4 cylinders, less than adequate for a car half its size
Crappy rear disc brakes, $19M class-action lawsuit settled
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Some other junk not worth mentioning

[jeepbob]

Save the champions for your ex mother in law and run Bosch supers, they seem to work much better in my 360. I also found that the AC plugs that are supposed to fit our motors are a 1/4" shorter than the recommended Bosch plugs and that may be a big reason I noticed the big difference, in fact I'm sure of it.

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65 wag. 360/edelbrock rb4/t400/20 t-case/4:10 d27/d44 broken power lok/onboard air/onboard 110v power(no inverter)/1999 Lincoln t.c.leather buckets/Lincoln ctr console/winch/33x12.50/tunes/water proof door pads
soon to have new motor/d44frt/d60r(4:10)welded diff/custom bumpers
see ya in da mud

[OBX-AUTOMOTIVE]

IN THE OLD DAYS,WHEN MOST, IF NOT ALL OF YOU GUYS WERE'NT BORN YET,WE,AS IN "GEAR HEADS",WOULD HANG OUT AND TALK CARS...THE TWO THINGS YOU NEVER PUT IN YOUR CAR OR ON YOUR CAR WAS,********CHAMPION SPARK PLUGS AND FIRESTONE TIRES*******GEMOBX

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[ironroad29]

10 -4 ON THAT SH#T GEM!!!!

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"If a jeep can't take you there, maybe you should think twice about going"