AMC 360 spark plugs--what are you using?

[rocklaurence]

Hey Guys, I fouled a plug the other day while towing [gap closed] and I replaced the plug with one from a salvaged motor [I'm cheap]. However, I want to change all the plugs to a PLatnium type [to go 100K miles] but I'm not sure what the compatible plug would be. What plugs are you using and what heat-range? Also, I'm running HEI with Mallory 8mm plug wires with no performance upgrades--its my Ugly shop truck.
Any comments are appriciated

[REDONE]

I'm using Champion 7405s in both my 401 and 304. I went round and round with plugs for a while, trying to treat other problems with plugs, but stem seals and intake leaks will foul any plug. I started with the Champion copper truck plugs and they fouled on holes 5&7 every couple hundred miles so I switched to Autolite platinums (like $7 a piece). After swapping the intake, carb and valve stem seals I switched back to Champion, but this time ran the platinums (7405s) and I'm happy with them.

From my research, using a high energy multi spark ignition with platinum plugs makes the temp range far less critical. Most platinum plugs are a "colder" temp rating because the platinum itself resists fouling. It's a noble metal so it doesn't oxidize allowing other materials to bond with it like copper or nickel. From my understanding, this is why most platinum plug manufacturers only make one or two plugs for each size instead of a range to pick from. If they make two, one will typically be much cooler and listed as a "racing" plug.

For those that want a quick primer on Spark Plug Temperature, it has to do with how much of heat the ceramic insulation carries out of the engine (to the plug wire boot end). If it takes away too much heat, the plug cools too much between sparks which allows the red hot electrodes to collect carbon and oxygen (fouling). If it doesn't take away enough heat, the electrodes stay so hot during the intake stroke that it can ignite the fuel/air before the spark plug fires. This is far more critical with low energy ignitions.

EDIT>>> In case you care, the reason I went with the Champions is that at the time, they were the only platinum plugs for our trucks not made in China, (they were made in Mexico). Don't know if they still are.

Double EDIT>>> Just went and checked and I still have 3405s in the 304, 7405s in the 401. The 3405s are the cheaper champion platinum. Seem to be adequate if I forgot that I hadn't changed them since 2011.

[letank]

Champion 404 (edit: or RN12YC), is the stock plug for our dinosaur technology, 405 is the hotter plug

http://www.ifsja.org/forums/vb/showthread.php?t=140251

or as said by hoot about platinum

Our engines and trucks are not designed to take advantage of high performance plugs. Waste of money in my book.

http://www.ifsja.org/forums/vb/showthread.php?t=108278

[derf]

I went with Champion RN12YC when I did the TFI upgrade. They're appropriate to the hotter spark of the TFI and work pretty well.

[Stuka]

I have typically always used copper core autolites. I stay aware from less efficient plug materials like platinum, as you will get a weaker spark. Platinum plugs are designed to last a long time, but require a higher output coil.

[memo43]

Im currently using ngk 4554, benefits it takes a 5/8
No issues with headers.
Good spark an could almost swear if I hold my tongue just right I get better gas milage.
That or my fuel gauge is still loopy

[rocklaurence]

Thanks guys, are you using dielectric grease or no-aux/never sceeze?

[REDONE]

I use copper anti-seize on the threads and dielectric grease on the boot.

[Rod2]

I've had NGK 7149 Iridium plugs in my truck since '11. Now, that's not many miles ago, but in an oil burning 360, I'm impressed.

[Nikkormat]

The only advantage to Platinum plugs in our dinosaurs is for plug life. And then, the cheap NGK Platinum (g power) are all you need. Plus the G Power plugs are designed to work well in old engines and small (think ATV) engines. But like others have said may actually hinder spark without a hotter than stock coil.

Over the past two years I've run AC Delco, Autolites, Champion, and finally NGK. The AC's worked well and looked darn good despite being 10+ years old. Replaced them when I put the new motor in. New motor ran Champions, had 5 of eight short internally over six months leading to misfires. Went to Autolites and they had fragile insulators, broke three installing them with a nice (neoprene sleeve vs plastic) sparkplug socket. But they work fine. This year on the three GW's I've put plugs in I used NGK G powers. Great quality, consistent gap out of the box, no failures during or after installation.

I replaced one set (of v power's) in the 89 which were installed 18 years and 20k miles ago. That wagoneer made a short 4 mile round trip everyday carting teenagers to highschool and then longer jaunts from Grant to Littleton​ every once and a while. Not exactly a long trip vehicle for the PO. I expected the plugs to be fouled up and nasty but upon inspection they looked more than acceptable. If it were my Jeep I would have run them longer...

Of course opinions on spark plugs are like opinions on light beer and oil. Everyone has a favorite and if you don't agree you're wrong!

[rocklaurence]

Thanks for everyones input. I did go with the NGK V power Platinum set to .040 on gap--I could have gone with more gap with the HEI but I kept it close to the .035 recommended. Good news, All the old plugs were tan and clean.
Also, replaced a leaking wheel cylinder on the D60. What a PNTA! Stupid retainer spring pins are too damn short making it almost impossible to get the hat on!!!!