4.7L spark plugs

[dakotapta]

Hey guys,
I am wondering of all of you that hve this wonderful 4.7L engine, and have changed the spark plugs, what plugs seem to work the best??? I am referring to the best HP increase and the best increase in MPG??? I currently have bosch platnum +4's which seem to run ok and what seems like a increase in HP, but it doesn't do much for MPG. So if anyone has any suggestions please let us know!!! thanks!!!

[illtmprdman]

WARNING -- WARNING -- WARNING -- WARNING

DO NOT USE *ANY* PLATINUM CORE PLUGS IN A 4.7L V8! THE CHRYSLER SHOP MANUAL FOR THE 2000 DAKOTA *SPECIFICALLY* STATES THAT PLATINUM PLUGS SHOULD NOT BE USED IN THE 4.7L V8!

A lot of things in shop manuals are written to make you buy Mopar replacement parts. However, one dealer (that I trust) gave me the poop on why the 4.7 SHOULDN'T use platinum plugs...

Instead of a standard ignition system, the 4.7 uses independent ignition coils on each spark plug. These coils are *EXTREMELY* picky about the resistance and conductive properties of the plug they fire. Likewise, platinum is totally different material than copper -- it has a greater resistance. Thus the ignition coils can't fire the plugs as quickly or as powerful as they could with a standard copper plug. This results in a horsepower and mpg LOSS. In addition, the higher resistance of platinum plugs can adversely affect the life of your ignition coils. Hence, DON'T USE THEM!

The best plugs for a 4.7L V8 are standard resistor copper-core plugs such as the Champion RC12MCC4's or the Autolite 5224's.

Contrary to popular belief, copper plugs aren't crap -- Edelbrock as well as Summit Racing reccommends them.

Sincerely,
ill-tempered man

[illtmprdman]

Oh, one more thing...

I run the Autolite 5224's -- my engine fires up right away and has plenty of power...

I get 15 to 20 mpg, depending how I drive

Sincerely,
ill-tempered man

------------------

2000 Dodge Dakota 4x4, 45RFE auto transmission, B&M transmission cooler, Borla stainless-steel shorty headers, Gibson 3" cat-back exhaust, Intense Performance "z-tube" air intake w/9" S&B big mouth filter, Derale engine oil cooler, Mobil1 synthetic oils (all the way around except front axle and trans).

[Brad Byers]

Ditto on the spark plug question. My dealership's shop foreman told me that they have swapped in other plugs only to have the owners bring their trucks right back in and have Champions put back in. This guy isn't opposed to mods, either. He's doing a sweet 1941 Powerwagon himself. He told me that even the Autolite plugs usually end up back in their original boxes on top of the dash in a week's time. I have to trust the DC engineers on this one; the Champion plugs that came in your 4.7 are the best for that engine. They have tested them all.

------------------
Brad Byers
Y2KOTA 4X4 CC
4.7 / 5-spd.
K&N filter, Gibson muff

[dakotapta]

Well i took your word for it and went and changed out the bosch plugs. I put in the autolite 5224's. It feels like i lost power due to this change, but if it will help out the MPG, i am all game. So we will see how they work out. Thanks for the info though....i also informed the local off road shop about what you said so they don't do the same to other trucks....

[Big Smoke]

I'm curious about the reasoning behind not using Platinum plugs.

I understand that platinum has a slightly greater resistance than copper. But if a manufacturer is making a plug as a direct replacement or cross-reference to another plug, shouldn't they be making it with the same heat range, resistance and conductive properties as the one they are tyring to replace. In the case of platinum versus copper they'd simply use less platinum in thier plugs to maintain the same resistive value.

Having said that, I checked www.boschusa.com and they have a vehicle search to find a plug for you. I searhed all three types of plugs listed and none of them offered a plug for my vehicle, including a copper plug.

I did another check on a few pages that had scans of plug charts and found a regular Bosch plug that crossed both the RC12MC4 and the 5224 you spoke of. It's a FR8LCX. Again, not a platinum. What I did find interesting though was that if you tried to cross the Autolite to the Champion you get RC12YC5. Some didn't list the MC4's so I'm assuming the chart was out of date.

In the end I'd have to agree with you not to use a Bosch platinum plug. Not for the same reasons though. OTOH, NGK makes a platinum plug but I haven't checked that.

Big Smoke
2000 Dakota CC Awd.

[dakotapta]

Hi, yeah i was jsut staing what i had heard from others. I do know that paltnium does ahve a slightly higher resistance. I have tried the plantium, and the regulars. The champions caused some hesitations and uneven idle, the platiums just caused the uneven idle to occur more...but with the autolite's i lost the hesitation and the uneven idle, but i wish i could just get that MPG back up there!!! but oh well....

[Jon_Smith]

I've heard good things about Bosch 4+ in the 4.7..... and I've heard mostely bad things about them in 5.2/5.8/3.9s... I run Autolite 3923's exclusively, after I found an 8hp gain on the dyno (gain over 24hr old Champions)... for my $9, I'd buy nothing but the autolites.

------------------
Jon Smith
Raleigh, NC
95 Dakota 4x4 CC
318, ported/polish heads, Crane Cam, MP PCM, 14x3 K&N, MSD digital 6 & Blaster SS coil, JBA headers, ASP crank pulley, Hayden 3710 fan, F&B TB, MPI intake, Crane 1.6 RR's, Hughe's dbl roller chain. 240+ rwhp
www.fast4x4.net