Spark plug removal From Aluminum Head

[Larry E. Howard]

Recently bought a 93 LT-1 and in the process of replacing the evaporator box while I have most of the right side engine compartment stripped out. I noticed a nice access to the number 8 cyinder plug. So I thought I would take a look at the condition of the plug. When I went to remove it, the plug wouldn't budge. I moved to number six and found the same. The car has just over 60K miles and I doubt the plugs have been out.
I am reluctant to use a longer ratchet without some advice, since these are aluminum heads and the plug may strip. Anyone have experience with this?

[Joe L.]

Re: Spark plug removal From Aluminum Head

Larry-----

This is a common problem with spark plugs in aluminum heads. From the factory, the plugs are supposed to be treated with an application of anti-sieze to help prevent this. In SERVICE, it's supposed to be applied whenever the plugs are removed and/or replaced. It wouldn't be likely that someone has replaced the plugs (and neglected to apply anti-size) at this car's mileage, but it's possible. Check them to see if they are AC 41-906 (you may be able to just barely see this around the porcelain with the boot off). If they are, the chances are they are original. If they're anything else (like Split-Fire, NGK, etc., etc.) then someone tried to "get fancy" and replaced them. They may have "forgot" to use anti-sieze when they did.

You have 2 options as I see it:

1) Leave the plugs that are in there. If they're the original plugs, they are platinum plugs with a 100,000 mile GM-recommended change interval. In that case, you've got 40,000 mile before you need to worry about them;

2) Change them and take the chance that you'll strip the threads when you remove them. That will require removal of the heads. There's NO "magic solution" for getting them out. All the penetrating oil in the world is unlikely to do any good, but you can try it; it can't hurt. An impact tool is going to be the best bet for removing them. As I say, you may strip the threads, but there's no way to avoid that if you want to get them out. You'll just have to take the chance on that if changing them is what you want to do.

[Clem Z.]

Re: Spark plug removal From Aluminum Head

use a "breaker bar" and give it a sharp blow with the palm of you hand. this will loosen the plug if it is not gauled to the head. if it moves a little i would squirt "kroil" penatrating oil in around the plug and wait 10/15 minutes and see how tight it is and if it move freely you are good to go. most of the time it is just carbon buildup on the threads that make them hard to remove. the "kroil" will disolve the carbon. they say never remove them when the head is hot because the aluminum is softer but also the plug hole in the head will be larger because the aluminum expands more than the steel plug shell and i have removed plugs from aluminum heads on race engines while the engine was hot with no problems.

[terry leeker]

Re: Spark plug removal From Aluminum Head

Larry this has work for me on AL heads (aircraft). Fire the engine up and get everything to operating temperature. Shut the engine off. Pull the plug wire and TIGHTEN the plug to say 20% over reccommended torque. Immediately remove the plug. I suggest you don't use an impact wrench. If it does start to come out and then gets tight, go to a light oil like 3in 1 on the base of the plug. Don't use WD-40, it has no lubicating properies what so ever. Then work it in and out. If you use an impact, it's all or Helicoil time.

[Chuck S.]

Re: Spark plug removal From Aluminum Head

Larry, Clem and Terry have the answer.

Get some gloves (long cuffs, but you'll burn yourself anyway) and change the plugs on the engine hot before it cools. The coefficient of expansion for the aluminum heads is greater than the steel plugs, thereby loosening their grip on the plugs ever so slightly when hot. Even hot, it may take a little care (see Terry's post above). If you try to change the plugs cold, it will be one of those things the GM service manual would tell you NOT TO DO (I can't remember if the manual actually covers it, but it should.) .

When you install the plugs, apply anti-seize lubricant to the threads. Don't over-do; I just fill the valleys flush to the peaks with the anti-seize (thats borderline overdoing), and wipe any excess well away from the tip.

I have a tube of Wurth high temperature, aluminum-colored anti-seize lubricant that really worked well in my 87. After my first plug change, I never had any problems removing the plugs. That tube is probably twenty years old and still like new; I just used it this past weekend to lubricate the backs of disc brake pads.

Wurth has a website that gives descriptions of their products. Import parts stores were once more likely to have Wurth than domestic brands; I got mine at a (gag) Volvo dealer.

[Duke W.]

Re: Spark plug removal From Aluminum Head

I'm not in the habit of using anti-seize on spark plugs in aluminum threads. My concern is that the compound might carburize and cause more problems than it will cure.

When using antiseize, I usually apply a thin ribbon along the thread shank, then wipe it flat with my finger. I then thread the bolt in and out a couple of times to evenly distribute a VERY thin film on all the threads. I've seen some plugs where the guy must have literally dipped the thread into a bucket of anti-sieze! You just need a very thin film evenly distributed on the male and female threads.

The other thing to pay attention to is installation torque. Typical taper seat spark plugs on modern engines are speced at 10-12 lb-ft, and, of course, I ALWAYS use a torque wrench to seat them within the proper specified torque range.

Duke

[terry leeker]

Re: Spark plug removal From Aluminum Head

One thing I forgot to mention, the combination of dissimilar metal corrosion and carbon infiltration is the culprit for plugs not just spinning out. Run a spark plug thread chaser throught the plug threads (NOT A TAP - if the head has ever been Helicoiled and you use a std. tap you'll be #^*!) before reinstalling the plugs each time you change plugs in a Al head. This takes care of the corrosion/carbon and cleans up any galling that may have occured when the plug was removed. If you are using the thread chase it will not be removing any metal. I agree with the other Gentlemen that a little anti-seize goes a long way. Be aware that if you are using a copper base anti-seize on internal engine parts and performing lube oil analysis, it can leach out and show up in your analysis as a high copper spike falsely indication trimetal bearing failure. A better choice is nickel based (silver color)componds which most oil analysis profiles are blind to.

[Clem Z.]

do not use too much antiseize because

it is conductive and will short out the plug. don't ask me how i know this.

[Larry E. Howard]

Re: Spark plug removal From Aluminum Head

Thanks for all the great input guys. I agree with Clem on the Kroil. I used to work at a fiberglass plant and the mechanics swore by "aero kroil". My can is over 25 years old and just about out, but on the numerous corvette restorations both on and off the frame, I found it superior to anything else. I used it exclusively three years ago on my 57 body off and never broke a bolt. Since I need a new can, if anyone knows of anything better please let me know.
Also, have lots of experience with anti sieze too. The spinners we used to make fiberglass, were bolted on and the shaft and nut were exposed to 2500 F. The "Never sieze" nickel base compound we, used kept the exotic alloys from sticking together in all but a very few cases. Never thought about the copper base stuff but that is all I have on the shelf so I guess I will use a light amount of it.
I am glad I posted cause I was never certain about hot vs cold. I will have to fire the engine dry, since to replace the coolant will cause me to lose my easy access to the plugs on the right side. I have done this on other engines in the past without any problems, but feel free to advise if you think there might be a problem.
Thanks for all the great input and oh yea the plugs are 609s so I guess they are originals

[William C.]

Re: Spark plug removal From Aluminum Head

Joe had a good point, you have at least 30,000 miles left on these plugs, why mess now?

[Clem Z.]

not to p--s in anyone corn flakes

but older AC platinum tip plugs have a nasty habit of losing their little platinum disks and you end up with a larger gap than spected

[Clem Z.]

PS the longer you leave them in

the harder it will be to get them out later. JMHO

[bruce11495]

Re: Spark plug removal From Aluminum Head

Replace the plugs NOW, if you are thinking of performance, mileage etc. The plugs won't go 100k like GM says...I had 80k on mine and they were the worst plugs I had ever pulled out of an engine of mine! The car was still running fine and the mileage was the same, but plugs were worn, dirty etc

[Larry E. Howard]

Update -- Success!!

I sprayed Kroil on number 8 yesterday so it had 24hrs to work, I fired the engine for about 45 seconds which had the head warm to the touch. Used my 1/2 inch drive torque wrench with a 3/8 adapter for the plug socket. With my hear pounding, gave it a crank. Didn't watch the reading on the wrench but I would guess it was less than 60 ftlbs cause it moved pretty easily. Initially I only moved it about an eighth of a turn. there was a lot of resistance, so I then sprayed some more kroil and let it set a couple of minutes. I then used the std 3/8 breaker bar and wrenched it a few turns and it loosened up with each turn. The plug threads were clean except for some carbon on the piston end for about the last 5 threads. Gap is in excess of .035.
Since my shop manual is "in the mail" maybe some one can tell me what the gap is supposed to be so I can put it back in and remove the others. I will get the torque readings on the next ones. I just sprayed them today so will wait til tomorrow

[Joe L.]

Re: Update -- Success!!

Larry-----

I'm glad it worked out. I'll remember this one of these days when I change the plugs on my 1992 LT1. I'm surprised that the Kroil helped the process.

Anyway, the plug gap should be 0.050".

What brand and type spark plugs did you take out?