Purchased Laser Iridium spark plugs for 99 F150 4.6. Noticed the threads on the new plug are located higher on the plug than the original OEM, will this create a problem?

 

This is not a "Site Announcement." Thread moved to appropriate forum.

 

i do know iridiums arent good for your basic, non performance engines. they burn too hot.

 

I put NGK irridiums in my 97 4.6 and didn't have a problem. Also didn't notice much if any change in performance. I'm back to the stock motorcraft part. Few more threads on the plug seem to work fine.

Good luck.

ihilani

 

Ford changed the spec plug on these motors about a year ago or so.
The 4.6 only has a low amount of threads in the casting.
The rest of the distance to the tapered seat is larger.
Threads all the way up to under the seat area will make no difference in these heads.
Some of the other Ford engines may use more thread making this plug more universal for them to use but never the other way around..
Otherwise there is no difference in the physical design 'except' the center electrode has about double the resistance of the original plug. Something no one ever checks and can make a difference under certain conditions. In any event, the original spec plugs are no longer available unless a dealer has some left.

 

hey thank you chieffx4 for the tip. could you tell me a good after market spark plug? looking for gas economy & long life. thanks

 

from experience i wouldn't go with anything other than motorcraft. i spent like 70 bucks on plugs and my truck ran like crap with them in. i don't think f150's like plugs that burn too hot.

 

I need some one to explain the following;
How a plug (of correct heat range) runs too hot in a stock unmodified motor that has no faults.
I see this assertion made twice in this thread, I and a lot of others people need to know form those people, how this works!
Don't bother with circumstancials such as a mechanic told me,, I replaced and the trouble went away etc. That is not showing whats wrong with a plug.
I want to know what is wrong and not with a lot of I hears etc.

Any product can fail no matter whoses it is. There is always a % of failures.
Coils fail often but no one condems them.
On a board like this you have to understand that you see a consentration of problems that makes things look worse than they are, overall.
If one never came to boards you would never know about lots of problems that you may (never have).
If every car and truck had a problem, we would all be back driving a hose and buggy. and worrying about vet bills and wheel bearings, instead.

 

http://www.centuryperformance.com/spark.asp
there ya go buddy... there should be some answers to your questions you are looking for. i didn't read the whole thing myself, just found it

 

the electrode (part where the spark comes from, not the half loop) on an iridium plug is smaller than a standard plug. this causes a more powerful spark which, in turn, makes more heat.

its not so much of a failure. more the way the plug is designed. iridium plugs are geared more towards high performance engines running high octane fuel (not even 93 octane qualifies for this).

 

Respectfully,
IZ, the referred website is fine. No problem with it. It dosn't answer my question. What is the problem with other plugs than Motorcraft?
If your not going to read it why refer it. <hear ya go buddy>

chief, It's baloney.
Heat at the tip {from ignition} is due solely to the energy supplied by the coil.
It's called 'power tranfer efficiency' and is only a very small percentage of what the coil circuit supplies. These system are very inefficient to the tune of less than 1% in there present form.
As for the Iridium plug designs, The metal is very hard and takes much higher temps to melt. The small tip makes ignition more likley under high pressures and difficult lean mixtures over the whole operating range due to it's small needle point area. Spark breakdown always favors sharp pointed electrodes.
The plugs have no way to supply any extra heat unto themselves.
The spark jump across the gap begins the Kernal that progresses as combustion. Any extra heat the plug sees is well ''after' combustion begins.
The spark it'self is very hi in temp for a few milliseconds only and errodes metal away from both the tip and the ground strap as in any other plug.
This is the reason all plugs have to be changed in due time.
This design in metal and electrode material makes them longer lasting and favor better hi performance applications, for which you also pay a premium in price.

Both of you should become better informed before making nonsense replies. Again, it is a demenstration of the "I heard, I read, They said" etc. Just doesn't fly with every body.
Why not learn instead of trying to argue points your not well informed about.
You have to go other places besides here to get a better education on these things.
This is why I meet so much resistance in trying to break the myths that prevail.
Honestly, I wouldn't be saying these things if I hadn't learn about them long ago.
Cheers.

 

i didn't hear or read anything i put more expensive plugs in my truck that supposibly burn hot and my truck ran like crap. once i swapped them back to motorcraft everything was great. I am guessing the term "hurn hot" has to do with the size of the spark. if you take a bosch 4 plug with 4 prongs compared to a regular plug with 1 you are going to get a bigger spark. I'm not trying to argue and maybe i came off that way. i don't know everything about spark plugs and not claiming to. i put plugs in my truck that produce more spark and i didn't have a good result. if this stuff is a myth, i would like to know myself what the truth is.
my apology...

 

4 ground electrodes do not give 4 sparks at the same time. (Another myth)
Only one gap breaks down at a time for each fire stroke.
It is dictated by the gap that will present the best ionizitation path at the time the coil voltage rises to the level of break down. These conditions change with rpm, throttle opening, differences in gas quality, combustion chamber turbulance and engine loading so is never constant.
This spark gap breakdown level is usually in the 7000 volt range.
Even though the coils are capable of 35,000 volts, that level is never reached and is considered reserve for the plugs that errodes over time tending the raise the breakdown voltage somewhat.. The rise in voltage is limited by the point the plug fires each time. The rest is waisted.

For the record, I do not reccomend any plug with more than one ground strap for truck applications or hi performance.
In lighter cars ok, on heavey vehicles, no. There is to much chance of over heating the extra ground electrodes during heavey loading and causing detonation.
Serious race cars don't even use these types.

If anyone wants to use BOSCH in a 4.6L then consider #6241. They are low cost and run fine. Change them more often for the cost and have a better running motor more of the time from that alone.

The remaining voltage after spark gap breakdown appears at the plug top. If the boot does not seal well, is hard and cracked, moisture is present, it arcs to the plug outer shell, tracks accross the plug insulator causing the rough running and missing. Since there is about 25,000 volts left +/- it tries to go somewhere if it is not contained within the plug boots seal.
This condition is often the point at which the coils can get damaged from internal breakdown trying to handle the excess voltage that didnot get dissapated at the time the plug fires normally.
From this you can see that higher voltage coils can make matters worse with the present hardware designs.

 

hey thank you bluegrass for the lessons on the spark plugs Sure help me make up my mind on which plugs to use. Boy these forums are great, wish we had this when I got my frist car a 32 Ford sedan for 900 bucks. In the early 60's , had to sell it to put a roof on my house 15 years later Put the new plugs in,test drive is good. Have to take my f150 to Cal. next wk see what happens Once again thanks a lot guys

 

Bluegrass I agree with you-this is a great forum but their is a lot of voodoo science stated as fact. kind of like the liberals in this country-the louder they yell the less factual their point!