Spark plug ?'s

stocker 89

Registered User
Just pulled what I am assuming are the stock plugs. Alot of miles on them. They are awsf 34pp. One of them was cracked. The ceramic part. So for now I replaced it with a bosch form advance auto.

Need to change out all of them . Going to in near future. Car is Stock 89 SC.

? Should I replace with motorcraft 34pp or should I use something different. I usually run 89 octane with ethanol. If I was to go 92-93 octane should I get colder range plugs. My thoughts are to just stay with what I know the 34pp they have always worked never had any problems with them.

Exactly what octane gas should I be using ? I have been reading many posts with guys reccommending the 32pp mustang plugs.

What should I do this time around. Any One have suggestions. If there is a better way to go I would like to know the reason why I should.
 
I would stick with the 34PP's. They are expensive, but they are the best for the stock SC's. People on here have had problems with Bosch plugs.

I would never run anything lower than 91 octane in a SC.
 
Stocker you need to run Premium fuel in the SC, Thats what it is set up to run on. You risk damaging the engine with detonation if you use lower grades of gas.
At the bottom of your tach you will see the words "Premium Unleaded Fuel Only" there is also a sticker under the fuel door covering the gas cap saying the same thing.
The stock heat range on the plugs is fine, stay with that.
The douple plats are better plugs and will last longer than the single plats but they are more expensive, so that part is up to you but stay with the stock heat range.
Stay away from Bosch plugs they will not work well in this engine.
Stay with motorcraft or Autolite.
 
OK I will stay with the stock one and give the double plats a try.

How do I know if I am getting the premium gas . There are some local gas stations around here that I feel are kind of suspect. I used to fill a motorcycle with sunoco cam III it did make a hugh difference. It probably should for 3.50 A gallon . But when I change to like standard BP / The Gold stuff from 89 ethanol to be honest I can't really tell a difference.
Should I be adding Octane booster or is it a waste of cash?

I sure hope you are correct about the double plats I will pay more if it is going to make a difference for the better . What is the # for the double plats 34pp double plat or what?

Thanks BlueThunder 90 I have also read many a posts about those bosch plugs have had no problems yet but I just put it in.
 
Well you wont notice any performance difference by using double plats vs single plats. The double plats just live longer so you wont have to change the plugs as often. Thats all.

Gas: You need gas with at least 91 octane. Every gas pump has a yellow sticker telling you the octane of the gas for that pump.
STAY AWAY from gas that is blended with alcohol. That kind of gas is BAD for forced induction engines like the SC. You risk having problems with the performance of the engine as well as possably damaging it.
 
On the fuel issue...

You're not going to notice a difference in fuel economy from 89 octane to 91 or higher. It is more complicated than the way I'll explain it, but it is the BOTTOM line for why we run higher octane...

The higher the octane, the higher the flash point of the fuel. So running 91 or 92 octane, you reduce the chance for detonation. On the flip side, if you run 89 octane you increase the chance for detonation. If you NEVER increase your boost level above "0" then running 89 will be ok, but we all know that part of the reason we have the sc is because of the boost... ;) My advice to you, run the higher octane fuel to preserve the life of your engine.
 
For spark plugs, I'll recomend what I'm using which is the NGK Iridium plugs. Just over $6 each from www.ngk.com. They are in my car and seem to be working just fine.
 
I would never recommend single plats for our engines since each bank of the engine fires in a different polarity. That means the spark jumps from center electrode to ground on one side and ground to center electrode on the other side. So double plats are in order, or just run the less expensive copper plugs and change more often.

I believe (in at least the 89 cars) a different plug went in each bank with platinum on just the electrode or ground to save a few pennies on each car!
 
I agree with you George but as its been pointed out to me cost is very much on some of the fellas minds. Thats why I mentioned both types of plug. I dont want to get in another brew ha because someone thinks I'm only recomending expensive parts.
 
No problem, Mike. I also realize cost is a concern to a lot of us. That's why I didn't want them spending on single plats as one side could wear out before the other. That would be a real waste and maybe even a crime in some states! LOL I'd prefer the less expensive copper plugs over single plats.
 
NGK iridium plugs have a standard ground electrode, so in a reverse firing situation like we have they won't last any longer than single platinum plugs. But you still get the benefit of a better spark kernel from the smaller electrode. They cost about the same as double platinum plugs.

I use NGK iridium but I don't really care about how long it lasts - my SC isn't a daily driver, and I can easily reach all six plugs from above anyway! ;)
 
Rob, that has kept me away from the Iridiums. Do you know of any brands that have iridium on both the center and ground electrode?
 
Thats the problem I have with Iridiums as well George. Every car I own has a wasted spark ignition on it with the exception of 1.
The Iridiums are of no advantage on a wasted spark system because they arent Iridium on both electrodes so they end up wearing out just as quick as single plats.
Might as well use single plats and save the money.;)
 
As far as I know, both Denso and NGK Iridium plugs (aftermarket) have a standard ground electrode. I have read that some OEM (rebranded ?) versions of the NGK plugs also have an iridium piece on the ground electrode (120,000 mile replacement interval!), you might be able to call NGK and see if there is an equivalent to the TR55-IX or TR55-1IX.

Mike the advantage of Iridium is not just durability, it's that the center electrode is much smaller in diameter, which creates a stronger spark kernel with lower voltage requirements. Helps prevent spark blowout and misfire on forced induction engines.
 
I didn't know there were platinum plugs with the small electrode, is it as small as 0.4mm (Denso) or 0.6mm (NGK)? Who makes them? If they are double platinum and have the small electrode that would be a good plug for the SC.
 
OK, this will solve it...

Stocker,
After the gut wrenching hours and busted knuckles trying to GET to your plugs, do you realy want to save $3 and do it all over again in half the time? You said they looked STOCK? There's a reason for that...it is called "I don't want to waste my weekend changing spark plugs". They made it that long right? Go for the more expensive if you can and you won't have to do it as often.
 
A big thanks to all.

I am gonna go with the double plats this time. Cause they are in order . The whole Gldiii post really convinced me with the electrode to ground ground to electrode explenation. Also they are supposed to last longer. Does any one have the motor craft or autolite part Number? I Know this is going to sound crazy BobGPZ but I kinda enjoy tearing the intake down working on it and then putting it back together. I find it very interesting. I always seem to learn something new everyday. I have did it quite a few times. I am actually gettting quick at it the first two times were a bummer but once you got the experience. You can really get good at it. The EGR has always caused me the most trouble. My biggest ? is why were they not double plats in the first place. Like the battery the 1000 amp does better yet it only comes with a 650 from dealer.
 
Stocker they didnt make double plats in 89 thats why they didnt put them in from the factory. I think they only started making them about 2-4 years ago.

As far as the battery who knows. The engineers that engineer the cars dont always have the finale say as to what parts get used in some places.
The car co's and I mean ALL of them have a team of what is called. "Bean Counters" The bean counters go in and look the new prototype over and try to find as many places to use parts that are already into production so as to cut cost of building the car and maximizing profits for the co. There have been many fights between engineers and bean counters over changes to the engineers original design.:)
 
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