New on the site, been trolling around and reading all the good posts. Now I'm going to ask my first question, got a 94 300 inline 6 and am wanting to put new plugs in it. What's the best plugs for that motor. Was looking at the Bosch plat. plugs but wanted to get some other opinions. Thanks inadvance for all advice.

 

motorcraft or autolite...fords dont like anything else

 

Always run Autolites, but I recently picked up some Bosch platinums super cheap on Rock Auto. Personally, I have no reservations about running them. My work truck gets whatever is cheap/on sale.

 

That engine will run just about any brand you can screw in the hole OEM plugs work just fine. On a personal note don't waste your money on exotics like E3 or other sooper dooper gona gain 100hp or 20mpg plugs. Oh and welcome to the forum where you will find a wide range of opinions and some BS just sort through it.

 

Motorcraft copper core or autolite copper core is the only thing to run in this engine's

 

Copper core plugs offer the lowest resistance. Our trucks use distributors and plug wires which create a lot of resistance. The more resistance the harder the coil must work to create a good spark. The down side is copper is soft requiring frequent maintenance and replacement. The up side is they are very cheap and produce the best spark. Platinum is much harder so it lasts longer ( up to 100k miles some manufactures claim). However they are at least 5x more expensive and greater resistance provides less spark with this system as well as higher strain on the other components. Irridium is a new metal being used in most modern coil on plug systems. It is harder than platinum and and more heat resistant with lower resistance. Because of the metals properties they design the plugs with a very small electrode to create an intense focused spark. However for these to work properly they each have their own coil at 50k volts and no wires or distributors to go through. Split fires, bosh + 4 etc use the idea that multiple contacts will create this storm of sparks all around. What really happens is the spark follows the laws of physics. Specifically electricity always takes the easiest path to ground. One part of one side electrode will always be closer or have less resistance than the others and that is where the spark will always strike until resistance changes for some reason. You can see evidence of this on worn splitfire plugs. The E3 plugs combine this idea with an old hot rod trick called side gapping. In side gapping, you cut the bent part off the electrode and make the proper gap to remaining side piece. This way the spark runs horizontally exposing it more to the air fuel mixture in the.cylinder. It works well on high compression or alcohol fueled race cars. But they toss plugs after a mile or 2.
So basically, the system was designed with copper plugs ( Autolite or Motorcraft specifically ) and they give the intended performance. Platinum will last much longer saving you some hassle, but will not provide the same spark creating possible issues of incomplete burn ( carbon build up , low power, low mpg, ) and greater wear on ignition components. Some of this can be overcome by updating the system with low resistance wires, cap and rotor, and high output coil.
In my opinion, you probably won't notice much difference for many miles. But on a truck with over 150k on the dial, and with copper plugs running for less than $1 each, I just run copper and get all the burn I can down there. I also have done the timing bump with requires greater spark to eliminate detonation.

 

Champion copper plus plugs have been good to me.

 

Warlockk or anyone with some experience using different plug types. Have you run a test to see any mpg difference between copper and platinum? I like to run plats simply for the fact they last longer, but I'm game to run some coppers if I could gain mpg and they'd last at least 25k.

 

I've never tested them myself. I doubt you'll see much difference. I do know its common to see a considerable overall performance difference when switching from worn plugs to new. That may be a factor to consider because the platinum will remain "newer" longer. I'm guessing of becomes a question of new plug performance vs long term cost. I think the bigger issue is deposits and completeness of burn. That you could probably check with an emissions analyzer and borescope.

 

Thanks for all the info, think I may go with the platinum plugs, like the fact those may have a longer life span. Truck has 170,000 miles on it too.