Originally Posted by Firestorm500

Sorry, I don't have it right in front of me. I got them from O'Reilly's 4 years ago. Any of them should be able to fix you up.

Originally Posted by cruiser54

I tried to cross reference/find those on the internet with no luck. I might check at O'Reilly's some time.

Originally Posted by CCKen

What's wrong with asking for a part number?

Originally Posted by investinwaffles

Honestly, I probably just like to wrench but I put in standard Champion Coppers and change them out every 20 to 30k miles (once a year for me).

Takes around 30 minutest to swap them all out for me, but I have the perfect wobble joint for the plug that's furthest back which makes it super easy.

I also wire wheel and polish the distributor cap + rotor because I am too cheap to get a new one but it seems to be working just fine.

Originally Posted by Firestorm500

Sorry, I don't have it right in front of me. I got them from O'Reilly's 4 years ago. Any of them should be able to fix you up.

Originally Posted by CCKen

Generally Iridium spark plugs are recommended for use in waste spark ignition systems, like the '00/'01 4,0.


Here's a spark plug application chart. These are all copper/double copper plugs.


For the '90 4.0 you may want to try the NGK FR5 plugs. Note the Champion heat range of "9". You want to stay in that heat range for the '90 4.0


Edit: I'm sorry if I offend, but I think using Iridium plugs in a non-waste spark engine is like putting lipstick on a pig.

Originally Posted by mschi772

Use the Champion coppers gapped to 0.035" especially if your ignition system is original. I have an MSD coil, Magnecore wires and upgraded battery cables, so I'm using Autolite iridium plugs gapped to 0.050". This works for me only because of all the other upgrades. My choice to use iridium was solely to see if the small electrode would further enhance flame kernel generation in combination with the increased gap. The bottom line is that they're working perfectly, but I'll probably go back to copper if I ever need plugs again--the small iridium electrode hasn't made a significant impact, and copper is a better conductor.

With a stock system, cap and rotor with brass contacts, Champion coppers, and Belden wires from NAPA are my choice and recommendation.

Originally Posted by adiga

really thanks .. i bought 8mm spark plug wires ... with this kit should i go with ngk or champion? or go with iridium ?

Originally Posted by CCKen

Your choice but I think you should stick with Champions and inspect/change them about every 20,000 miles.


Kit? Don't forget cap and rotor. I recommend Echlin parts from NAPA. Cap and rotor should be a matched set.

Originally Posted by Bustedback

That .050" gap is putting a lot of stress on the ignition system for hardly any gain.

Originally Posted by mschi772

I'm well researched, experienced, and don't just do things *****-nilly. I know my ignition system doesn't manufacture rainbows while curing cancer, but as a system and in conjunction with the rest of my mods/build, I'm getting what I hope to out of it. The iridium is actually the least beneficial part, and if they ever crap out, I'm going back to copper but keeping the 0.050" gap. My MSD coil and Magnecore 8.5 mm wires are doing just fine, thank-you.

Originally Posted by CCKen

Generally Iridium spark plugs are recommended for use in waste spark ignition systems, like the '00/'01 4,0.


Here's a spark plug application chart. These are all copper/double copper plugs.


For the '90 4.0 you may want to try the NGK FR5 plugs. Note the Champion heat range of "9". You want to stay in that heat range for the '90 4.0


Edit: I'm sorry if I offend, but I think using Iridium plugs in a non-waste spark engine is like putting lipstick on a pig.