Aluminum heads and spark plug seizure

[Man In Black]

My corvette still has low miles so I'm not concerned right now but I was curious how many of you with high miles like 100k or more encountered thread seizure when you went to change your spark plugs . This is a common problem with aluminum heads so it is recommended on some cars to use anti-seize but if it was not used before when you try to remove the plugs it can pull the threads out with the plugs , ruining the head. When I am removing anything from an aluminum head or block I alway just turn it slightly one direction then reverse the direction continuously a little at a time until it starts to move freely. Since our plugs are supposed to last 100k. I thought I would make anyone aware of the potential problem before it happens. I just went through this with my wifes Toyota a couple days ago . The plugs were very tight. They eventually came out ok with no thread damage and put back in with anti-seize.

 

[Huskerman]

I changed my plugs on my C5, when I still owned it, at 90K and had no problems getting the plugs out. I'm convinced they were the original plugs. They were tight but I was just busy marvaling at how easy it was to change the plugs in the C5 Vrs. my C4 when I had it.......... I did change out the plugs in my GS this winter at 25K just because I wanted to mess around with it.......I did use anti-seize.....

 

[Man In Black]

I changed my plugs on my C5, when I still owned it, at 90K and had no problems getting the plugs out. I'm convinced they were the original plugs. They were tight but I was just busy marvaling at how easy it was to change the plugs in the C5 Vrs. my C4 when I had it.......... I did change out the plugs in my GS this winter at 25K just because I wanted to mess around with it.......I did use anti-seize.....

I have heard that the plugs used in the C5's have a coating helping to keep them from seizing but I think it couldn't hurt to use anti-seize compound to be sure.

 

[Hib Halverson]

My corvette still has low miles so I'm not concerned right now but I was curious how many of you with high miles like 100k or more encountered thread seizure when you went to change your spark plugs . This is a common problem with aluminum heads so it is recommended on some cars to use anti-seize but if it was not used before when you try to remove the plugs it can pull the threads out with the plugs , ruining the head. When I am removing anything from an aluminum head or block I alway just turn it slightly one direction then reverse the direction continuously a little at a time until it starts to move freely. Since our plugs are supposed to last 100k. I thought I would make anyone aware of the potential problem before it happens. I just went through this with my wifes Toyota a couple days ago . The plugs were very tight. They eventually came out ok with no thread damage and put back in with anti-seize.

Seized spark plugs are a problem only if they've either: 1) been overtightened (when in doubt, use a torque wrench) or 2) people try to take them out of a hot engine.

With Corvette aluminum heads, provided the plugs are installed properly, antiseize is not necessary. Just the fact that the plugs in your Wife's Toyota were very tight but came out clean is proof of that. On the other hand, given the proper type of antiseize, it won't hurt. This issue of proper installation is misunderstood by many. Since 1992, plugs used in Corvette aluminum heads have used tapered seats and taper seat plugs can easily be overtightened by people used to working with flat seat plugs having sealing washers.

Taking care of plug threads is key. If the engine is dirty, I take shop air and blast the area around the plugs to remove dirt and debris before I take the plugs out.

If you are going to use antiseize, non-metallic antiseize is a must. I use DuPont Krytox but there are a variety of non-metallic antiseize compounds available.

I think plugs lasting 100,000 miles in a Corvette engine is some parts marketing guy's wet dream. In my experience, in high compression engines which are sometimes run hard, OE plugs never last 100,000K and still perform well. You may get 50,000-65,000 but not 100K.

Since the early-'00s, my favorite replacement plug is the Denso Iridium Power in which Denso crossbreeds some of it's OE technology (Denso has been a GM supplier for a long time) and some of its racing spark plug technology. They have a small diameter iridium tip and a cut back and pointed, u-groove side electrode and work very well in Corvette engines.

 

[Man In Black]

Seized spark plugs are a problem only if they've either: 1) been overtightened (when in doubt, use a torque wrench) or 2) people try to take them out of a hot engine.

With Corvette aluminum heads, provided the plugs are installed properly, antiseize is not necessary. Just the fact that the plugs in your Wife's Toyota were very tight but came out clean is proof of that. On the other hand, given the proper type of antiseize, it won't hurt. This issue of proper installation is misunderstood by many. Since 1992, plugs used in Corvette aluminum heads have used tapered seats and taper seat plugs can easily be overtightened by people used to working with flat seat plugs having sealing washers.

Taking care of plug threads is key. If the engine is dirty, I take shop air and blast the area around the plugs to remove dirt and debris before I take the plugs out.

If you are going to use antiseize, non-metallic antiseize is a must. I use DuPont Krytox but there are a variety of non-metallic antiseize compounds available.

I think plugs lasting 100,000 miles in a Corvette engine is some parts marketing guy's wet dream. In my experience, in high compression engines which are sometimes run hard, OE plugs never last 100,000K and still perform well. You may get 50,000-65,000 but not 100K.

Since the early-'00s, my favorite replacement plug is the Denso Iridium Power in which Denso crossbreeds some of it's OE technology (Denso has been a GM supplier for a long time) and some of its racing spark plug technology. They have a small diameter iridium tip and a cut back and pointed, u-groove side electrode and work very well in Corvette engines.

You misunderstood what I said about the Toyota plugs. They didn't just turn hard from the seat which would mean overtightening , they ran hard almost all of the way out and if it weren't for slowly moving the plug back and forth until it was almost out it would have pulled the threads out with it. The threads were not clean , they had heavy oxidation buildup on the threads which is common with aluminum heads. I've seen more than one head ruined this way when someone gets in a hurry and just keeps forcing the plug out before the oxidation is worked off of the threads. That was the point of this thread.

 

[Junkman2008]

Changed my original plugs at 90K and they came out easy as pie. Had to change them again at 140,000 and again, easy as pie. Iridium plugs do not need anti-seize.

 

[Man In Black]

Changed mi original plugs at 90K and they came out easy as pie. Had to change them again at 140,000 and again, easy as pie. Iridium plugs do not need anti-seize.

Yes I heard that about Iridium plugs ( might have been you that said ) but someone had put regular plugs in the Toyota and they were a bear to get out. I replaced them with Iridium . Unfortunately some people use standard plugs with no antiseize and cause the problem. Steel against aluminum just seems to gauld through time on things like threaded plugs. Thanks for your opinion Junkman. We know when it comes from you , it has to be right !

 

[Junkman2008]

Yes I heard that about Iridium plugs ( might have been you that said ) but someone had put regular plugs in the Toyota and they were a bear to get out. I replaced them with Iridium . Unfortunately some people use standard plugs with no antiseize and cause the problem. Steel against aluminum just seems to gauld through time on things like threaded plugs. Thanks for your opinion Junkman. We know when it comes from you , it has to be right !

Stop it. I can't fit most of my hats as it is.

 

[LLC5]

Yes I heard that about Iridium plugs ( might have been you that said ) but someone had put regular plugs in the Toyota and they were a bear to get out. I replaced them with Iridium . Unfortunately some people use standard plugs with no antiseize and cause the problem. Steel against aluminum just seems to gauld through time on things like threaded plugs. Thanks for your opinion Junkman. We know when it comes from you , it has to be right !

Actually G.M. says not use antiseize on the spark plugs. Instead they say to use about one drop of synthetic oil on the spark plug threads, then install and torque to spec's.

 

[Huskerman]

Actually G.M. says not use antiseize on the spark plugs. Instead they say to use about one drop of synthetic oil on the spark plug threads, then install and torque to spec's.

That is so right......and I remember that is what I did for the GS this winter......forgot all about that........good call LLC5 guy....

 

[c4c5specialist]

Hi there,

Also an important point to remember, the electro plating of the sparkplugs on OEM applications IS an anti oxidation coating.

This is why YOU NEVER EVER use a wire wheel to clean the threads, as this process takes off the electro-plating and thus the antioxidation characteristics of the plug itself.

Also to a point, regardless of the antiseize taking out the threads of the cylinder heads, it also can inhibit ground source from the grounding electrode back to battery negative. This can also micromisfire the sparkplug, resulting in fuel loading of the catalytic converter leading to its failure prematurely.

Allthebest, Paul

 

[dougelam]

After 28yrs of wrenching I can barely remember maybe a handful of times the threads pulled and it was a long time ago at that. If I remember correctly I believed that they were damaged from the time that they were put in and not from me trying to remove them. I'm willing to bet like Paul stated someone cleaned old plugs and put them back in. If they are out and in my hand they get replaced.

 

[gmjunkie]

Changed my original plugs at 90K and they came out easy as pie. Had to change them again at 140,000 and again, easy as pie. Iridium plugs do not need anti-seize.

106,000 on mine when I changed out the OEM plugs and wires last month at it's first scheduled tune up!(6,000 mi late):L

No Problem removing them and they actually looked darn good,I think I could have re-gaped them and put them back in for at least another 30,000 mi!

 

[Hib Halverson]

Keep in mind that the term "iridium plug" does not refer to the material used to make the plug body. That's steel which is sometimes "electro plated" as pointed out by "c4c5specialist".

An "iridiuum plug" has a center electrode tip made of an iridium alloy. Iridium is used because it has less resistance than does platinum but as good or better durability.

The first use of an iridium-tipped plug in a Corvette was in the early-'00s and Denso was the supplier.