Changing spark plugs early in Aluminum Head cars

plug
ford
mustang
sparkplugs

#1

I changed the plugs in my car at approx 40,000 miles instead of the prescribed 100,000 miles as recommended by FORD. When I looked at the old plugs I did not find any soot, but some powdery rust at the hot end. I was afraid of the threads galling if I left these plugs in there. What is your opinion, did I just waste my money or is it good if you plan to keep the car for next 20 years.


#2

I’m of the opinion that you did the right thing. Not only has any potential thread galling been headed off before it starts but I have yet to see a 100k miles spark plug that looked fine.


#3

I changed the plugs in a Vic 4.6L at the recommended 100K interval without any problems…If you use an anti-seize compound on the threads as the factory did, extended service intervals are not a problem. Yes, the ground electrode was well worn, the gap about .080", but no misfire problems resulted. The coil-over-plug system throws a POWERFUL spark…The new double-platinum plugs should go even longer. Life-of-the-car spark plugs can not be far away…In the future, cars that require a lot of maintenance will be ignored by the consumer in favor of “maintenance free” models…


#4

I hope that you just snugged the spark plugs, and that you didn’t tighten them “real good”. “Snug” is about 15 to 20 ft. lb. (preferred). “Tight” could be over 40 ft. lb. (NOT desired).
Look at these spark plugs and compare to your old spark plugs. How would you say your car was running, from your “reading” of the old ones? http://www.autolite.com/pdf/PlugTips.pdf


#5

I changed the OE iridium plugs in my car at the prescribes 120k mile mark with no trouble, and the old plugs actually looked pretty good and still worked fine. If you properly torque them and use anti-seize you shouldn’t be afraid of leaving your plugs in as long as is recommended by the manufacturer.


#6

I only went to 1/4 turn past the 15 ft-lb. My old spark plugs look rusty on the hot end it is powdery rust. I cannot tell the difference in performance too many intrusive computers, maybe at the end of the week, I might see some difference in MPG.


#7

Oh and I used anti seize also. The good hit Temp stuff.


#8

“Life-of-the-car spark plugs can not be far away…In the future, cars that require a lot of maintenance will be ignored by the consumer in favor of “maintenance free” models.”

The end of the spark plug as we know it may be coming to an end in the near future, according to a small article in the current issue of Business Week.

The article states that Ford is working, in conjunction with The University of Liverpool and GSI Group, on the use of “compact lasers” in place of spark plugs. It goes on to state that these compact lasers would have the advantage of being “better aimed and timed” to ignite the mixture in the combustion chamber, and that this would lead to more power, higher fuel efficiency, and less pollution.

If these compact lasers turn out to be truly lifetime components, this will be a great advance in automotive technology. But, of course, we will see failures of ths component in the field, and the cost to replace an out-of-warranty laser might be in the YIKES category. And, of course, then we will likely see dealers advising naive car owners that their lasers need to be cleaned and polished.

But, since the spark plug has been with us in one form or another since the dawn of the auto age, it does seem like modern technology might be able to come up with a better device. Time will tell.


#9

You overtightened the spark plugs. I said, “snug”. The Ford repair manual says to torque the spark plugs to: 7 to 15 ft. lb. It does NOT say to turn the spark plug an additional 1/4 turn. No. A spark plug is NOT a structural fastener.


#10

What is the solution. Should I loosen them and re-torque to 15 ft-lb? I hope I didn’t damage the threads.


#11

I would never tighten a spark plug to 15 ft. lbs in an aluminum head engine; especially a plug with a tapered seat.
In a case like this 15 ft. lbs of torque may not strip threads but it can “pull” them, which means the threads are distorted by being forced upwards. At some point in time they may strip on out; either by combustion forces or by repeated changes of the plugs.

Follow this board for a while and you will see regular posts about the evils of leaving plugs in place for too long.
Some get away with it and for the ones that don’t it can be an expensive fix if they have to pay someone to repair the threads.


#12

I think that’s not a bad idea. By going to 15 ft-lbs and then another 1/4 turn, they’re probably at least 25 ft-lbs or more by now, and that’s too tight.

Remove them (when the engine is COLD, before it’s been driven for the day), and when they’re tightened to where they don’t turn freely anymore, just bump them snug. We’re talking about 1/16th of one turn, more or less. An even better idea is to use a torque wrench if you have one.


#13

I have to disagree on the anti-seize. The torque specs for the Fords I work on are for dry threads. The anti-seize will lube the threads and change things. The nickel plating on the plugs is all the anti-seize you need and want.

I changed my plugs in the 4.6L Ford product at 95% of the recommended service interval (95,000). They looked very good. The plugs in the pic look like they are from a 4.6 or 5.4 with a 3-valve head. IIRC, there are some problems with carbon build-up around the long extensions below the threads making removal difficult. I think there is a TSB recommending soaking the well with some kind of solvent overnight. I would look into it if I had that kind of engine.