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Discussion Starter · #1 ·
Does anyone have any recomendations for spark plugs, wires, cap and rotor for a '94 Jeep YJ Sahara? I'm not real familiar with all of the brands and was just wondering what to get. I don't mind spending the $$ on performance parts....

Steve (that annoying guy who is just getting into automotive rebuilding and has a TON of questions, it also doesn't help that none of the people I hang with are into doing the work themselves, so I'm teaching myself /wwwthreads_images/icons/smile.gif)
 

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/wwwthreads_images/icons/smile.gif He who asks no questions, stays dumb./wwwthreads_images/icons/laugh.gif I don't have an answer for you, but get ready for an landslide. That's almost like asking about tires, you get a lot of input./wwwthreads_images/icons/wink.gif

CJDave
 
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Discussion Starter · #3 ·
IN my opinion, find out what is factory, and use those plugs. Here is the rundown:

1. Don't buy the funky designer plugs. If you want one with a fork in the strap, file it yourself. An old grag racer trick is to file the strap to a point. Don't know if it actually works - the only fancy stuff I've ever done was indexing plugs, and that is a huge pain for the minimal gains that you get.

EXEPTION - AC DELCO RAPIDFIRES. There is a dyno shop that a good friend told me about. The owner started using Rapidfires in engines that he was testing, and found them to be excellent plugs. However, he kept getting customers coming back unhappy. Turns out that when they got home, put their plugs in and everything, the engines weren't running right. Apparantly the Rapidfires were so efficient that they were covering up fuel problems and mixture imbalances.

2. Platinum plugs will NOT increase power, only increase the length of time between plug changes. If you're like me, and grit your teeth every 25,000 miles because you HAVE to change your plugs, then platinum tipped plugs are not for you.

3. Bottom line, like I said, I've always seemed to have the best luck with using whatever came from the factory. However, in my '94 YJ 4.0, I upgraded the to Champion's "Truck Plugs" due to claims of increased resistance to vibration, but the added cost was minimal. I have been happy with those plugs so far.

As for wires, I had a set of Jacobs wires on a pumped 350 once. Great warranty - if you ever burn one, they replace it. You can't beat that with a bat! Plus, they're a cool blue color, and you fit them yourself, so they're exactly the right length for what you want.

I don't even know if anyone makes caps and rotors for the 4.0 other than Mopar and the regular Kragan's and Pep boys brands. If MSD made one, I'd would buy those - they are a high quality part.

Everything stated herein is the sole opinion of the author. If you don't agree, them write your own post. :)

Hope this helps...

Marc
Contagious Racing
 
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Discussion Starter · #4 ·
It might be just a weird quirk, but I have used Champion plugs on every American made machine I've owned for 30 years. For the
rice burners the only plug I ever used is NGK. But, that's just me.

Brad (from the 4 Wheeling center of the universe, 4 corners USA)
 

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/wwwthreads_images/icons/wink.gif There is much debate about plugs among the forum's bretheren/wwwthreads_images/icons/smile.gif .....but I'll share my experience with you and let you form your own opinion /wwwthreads_images/icons/wink.gif
I've had the best results with Bosch Platinums ..... the old style .... in over 40,000 miles of checking the mileage at every fill up (this was a passenger car) I had no degradation in fuel economy or performance and they're still going. I've got the Bosch Plat +4s in my 92 Caravan ...... for about 10k.......so school is still out...... but when it comes time to change the plugs in the 99 TJ ..... I'll probably go with them.
Splitfires ...........everyone that I know that have used them says that they deliver more punch but less fuel economy ....... even the guy at the parts counter says this ..(no one has given me an explanation for this)..... but I've never used them.
The Jacobs wires are of a really low resistance ..... the theory being that more of the voltage (pressure) can be, when used in conjunction with a wider gap at the plug, disapated over the gap ....instead of being dissapated in the resistance of traditional resistor wires. This should be true whether or not you use the rest of the Jacobs system .....it's just simple electrical theory. The Jacob's wires supposedly have 100 ohms/inch as opposed to the 1000 ohms/inch that conventional wires have. The Jacobs coil is supposed to "sense" the feed back of changing cylinder conditions due to pressure and fuel density and "reactively" adjust the output of the coil.
The filing to a point thingie is an older trick and is based on the theory (fact actually) that an arc makes easier contact with a pointed surface as opposed to a flat one.......I guess it's like the tallest thing in a lightening storm thingie. It's not practical today because of the accellerated wear of the pointed surface .....and since there are an abundance of special application plugs for the HI-PER market that supposedly do a better job.

......"and now (to quote..well paraphrase actually.. Paul Harvey)....you'll get the rest of the story."(from everybody else) /wwwthreads_images/icons/wink.gif

"The only stupid question .......is the one that is never asked" ........... answers, however.....well that's another story/wwwthreads_images/icons/smile.gif

GeeAea
 
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Discussion Starter · #6 ·
Okay, with a question like that, you're really asking for opinions. Everyone has a different opinion on what plugs are best, etc. So, here's mine...
Plugs: AC Delco Rapid Fire - without a doubt, the best plugs I've used
Wires: MSD Super Conductor - Test them yourself... lower resistance means more spark at the plug.
Cap & Rotor: Varies depending on whats available. I like the performace set made by accell (they have brass inserts for better conductivity and longer life), but when I bought the set for mu '90 4.2, I couldn't find Accell, so I bought Borg / Warner's Nascar series set at the local parts store (seem to be pretty well made, but I haven't had them in long enough for a final judgement).
If you want the most performace from your vehicle, I'd recommend springing for a perfomace coil as well. Accell and MSD make nice units, I really like the Jacobs Ultra coil, but it's kinda pricy for a coil. Before you can build an engine up to give you more power, you've gotta burn the fuel you're already using. You're on the right track, and you're lucky to have discovered this forum. There's a lot of great info here, as well as some pretty decent opinions. Hope this helps, and happy Jeepin'!

-Spyder
 

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/wwwthreads_images/icons/tongue.gif I'm with Spyder on the Borg Warner wires....they work SUPER in the small block Chevys./wwwthreads_images/icons/cool.gif

CJDave
 
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Discussion Starter · #9 ·
Interesting idea, but indexing your plugs would give about the same result, without loosing so much plug life. The "side gapped" plugs will wear out faster. What your trying to do it expose the spark to the greatest area inside the combustion chamber. This is the reason folks index their plugs to begin with. It can be a little bit of a pain, but I've been indexing my plugs for several years, and I can definately tell a difference in power, and mileage (although it is a slight one). Just for fun, I might try that "side gap" idea, and index them, just to see if I can tell a difference, but when you direct the spark to one edge of the electrode, you will shorten the life of the plug considerably. As long as you're willing to replace them a lot more frequently, I say go for it. Just my thoughts... Happy Jeepin'!

-Spyder
 
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Discussion Starter · #10 ·
The plugs I tried it on were Autolite Copper Core plugs I got at Napa for $5. I don't know how long they'll last but for $5 I can replace them often. /wwwthreads_images/icons/cool.gif

Nick Hagen
1995 Wrangler
33" Mud Tires and a four banger
 

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Hmm...theres lots of other interesting documents at that site too. Thanks for the link.

Spyder,
Would you be interested in giving a quick lesson on plug indexing?

'79 CJ-7
 
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Discussion Starter · #12 ·
Re: Spark plug indexing...

Sure, basically, you are screwing the plug in so that when snug, the electrode doesn't shield the spark from the rest of the combustion chamber. This prevents the fire from going from the plug to the close edge and "bouncing back" to the main portion of he chamber, resulting in slight detonation and poor combustion (read: loss of power, bad fuel economy, higher emissions, etc). What you want to do it make sure the "open side" of the plug it pointed at the largest area of the chamber. In the AMC I6's, this means the "open side" should point up (the electrode should stem from the bottom). To do this, is really no harder than a regular plug change. I'll give you a quick step by step....
1. On eack new plug, take a black permanant pen and make a mark on the plug, down the insulator, on the "open side" of the plug, making sure you can see it when you look straight down on the plug from the wire side.
2. With a set of indexing washers (available as most parts stores, speed shops, and Summit racing will send 'em mail order) ready, insert the first plug and tighten to specs.
3. Note the position of your black mark - if it doesn't point the right direction (it should be at approx 12:00 for 258's and 4.0's) remove it and add the appropriate number of washers.
4. Repeat steps 1 - 3 for each plug.
Note: Use as few washers as possible to achieve the proper position. The last set of plugs I installed in my '90 were AC Delco Rapid Fires, and I was able to get them indexed without ANY washers. This was a first for me, but I don't think it had anything to do with the plugs themselves, just luck. I only mention it because its worth saying, you don't always need a washer on every plug. Just dont force them by over torqueing (sp?) or leaving them a little loose. Hope this helped. Happy Jeepin'!

-Spyder
 

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Re: Spark plug indexing...

Caps and rotors - Blue Streak. Do not get anything that does not have brass inserts in the cap.

Plugs - I've had good luck with the Nippondenso u-groove. Otherwise, it's just basic Champion.

Wires - Accel.

I had a Jacobs ignition OMNI Pak, -- not impressed.
Good luck
Pete

88YJ,4"susp,33"BFGMTs,9000#winch, hm swing out TC/HL mount ,258,999,4.10,weber32/36,GMHEI.
 
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