When the head is hot, the aluminum expands in all directions wrt to the steel of the spark plugs (...the hole gets bigger...)... all directions includes the "vertical" direction (i.e. along the spark plug bore centerline)... this causes the aluminum threads to bind/lock on the steel threads... various service manuals show diagrams of this;
this is why you shouldn't remove the plugs from a hot aluminum head... it risks pulling the aluminum threads out...
But, you had something else going on:
- overtightening of the plugs,
- corrosion in the steel plug material (weakening like you said),
- binding for various reasons (no antiseize, heat, possibly even steel-aluminum electrochemical reaction),
all came together to cause trouble.
Hope you're feeling better, and hope you get it all fixed up soon (nothing's worse than being sick and then have your car break on you).
When the head is hot, the aluminum expands in all directions wrt to the steel of the spark plugs (...the hole gets bigger...)... all directions includes the "vertical" direction (i.e. along the spark plug bore centerline)... this causes the aluminum threads to bind/lock on the steel threads... various service manuals show diagrams of this;
this is why you shouldn't remove the plugs from a hot aluminum head... it risks pulling the aluminum threads out...
But, you had something else going on:
- overtightening of the plugs,
- corrosion in the steel plug material (weakening like you said),
- binding for various reasons (no antiseize, heat, possibly even steel-aluminum electrochemical reaction),
all came together to cause trouble.
Hope you're feeling better, and hope you get it all fixed up soon (nothing's worse than being sick and then have your car break on you).
Cheers
Joe
Thanks Joe... I don't know why there would be a steel-aluminum electrochemical reaction... i mean it makes sense, but so many others on here are running NGK's with AFR heads with no issues... but all your other points make total sense...
I'll go over to my buddies house and take some pics of the car tomorrow and post em up for everyone... Probably won't be able to actually work on the car though for a few days or so... work + school = little money and no time
talked to a machine shop today... this was pretty much our conversation....
Roger: why did they put anti-sieze on there?
Me: ...... well..... that's what your supposed to do.
Roger: no your not... your supposed to put dio-electric grease on there.
Me: yea on the connections... not the threads
Roger: No... your supposed to put it on the threads...
Me: :wtf:
Me: why would you not use anti-seize on the threads and put dioelectric grease on there?
Roger: the anti-seize will stop the spark plug from creating current and making a good ground...
Me: ...... uh.....
Roger: Real race shops use dio-electric grease...
Me: oh... well ok then Roger, thanks, talk to you later
so......... I guess I'll keep searching for another shop
WTF????
BTW, who put those spark plugs in? I just tighten mine by hand pretty snug but I know not to go too crazy on them. They are only supposed to be torqued to 15 lb/ft. And of course i put anti-seize on the threads. This sucks for you and now i worry about future removal of my spark plugs lol.
Sorry to hear about your problems, hopefully you'll figure everything out. I can't believe the machine shop didn't use anti-seize.
You don't need much anti-seize at all. Just a little at the threads closet to the electrode. When you install the plugs, the anti-sieze will work it's way down the threads.
K guys... got some pics of the heads finally... in the first post...
I'll try and get some more of my engine bay tomorrow... when I went to my friends house to get these pics I forgot my damn keys to the car so I couldn't open the hood
Seeing as how that's an aftermarket cast head, maybe the metal-metal chemical interact theory holds some credence? Does anyone know the differences in the materials and how GM heads and AFR heads are cast?
talked to a machine shop today... this was pretty much our conversation....
Roger: why did they put anti-sieze on there?
Me: ...... well..... that's what your supposed to do.
Roger: no your not... your supposed to put dio-electric grease on there.
Me: yea on the connections... not the threads
Roger: No... your supposed to put it on the threads...
Me: :wtf:
Me: why would you not use anti-seize on the threads and put dioelectric grease on there?
Roger: the anti-seize will stop the spark plug from creating current and making a good ground...
Me: ...... uh.....
Roger: Real race shops use dio-electric grease...
Me: oh... well ok then Roger, thanks, talk to you later
so......... I guess I'll keep searching for another shop
Stay far, far away from that shop.
Anyway, I have had that happen on iron heads but never aluminum. You should be able to pull those right out with an E-Z out now that the heads are off of the car. Put some Aero-kroil on them overnight and they'll come out in the morning. As posted above, never pull plugs from a hot head... it can only CAUSE trouble. Are you running some kind of octane booster or fuel additive? It looks like you've got some strange discoloration for normal pump gas. If you are using something, it could be causing a chemical reaction. I am used to seeing some oil leeching up through the threads if anything...
Hope this helps.
Shane
__________________ "Killing internet myths... one post at a time..."
2000 Pewter SS-M6 #2515
408 SR ET LS7 in the works...
2005 Redline CTS-V stock?!?!
12.97 @ 112.90 2.36 60'
I only have 1 spare rear end...
Anyway, I have had that happen on iron heads but never aluminum. You should be able to pull those right out with an E-Z out now that the heads are off of the car. Put some Aero-kroil on them overnight and they'll come out in the morning. As posted above, never pull plugs from a hot head... it can only CAUSE trouble. Are you running some kind of octane booster or fuel additive? It looks like you've got some strange discoloration for normal pump gas. If you are using something, it could be causing a chemical reaction. I am used to seeing some oil leeching up through the threads if anything...
Hope this helps.
Shane
Thanks for the input Shane
yea, I found another shop that also mentioned an easy-out method and they said they'd get it done right. If they couldn't do it, then they said they know another shop that they use for tough jobs like this that can... so, that makes me feel a little better... gonna drop my head off to them on Wednesday
as far as the discoloration goes... what parts are you talking about specifically?
no I'm just using regular 'ole 91 octane chevron gas
The red streaks and the greenish tint of the insulator. Also, there is some greenish gray pitting on the threads... Its really strange that his happened to you. NGK's come with a coating to prevent gaulling in aluminum and may normally be used with or without anti-seize.
Let us know how it comes out...
Shane
__________________ "Killing internet myths... one post at a time..."
2000 Pewter SS-M6 #2515
408 SR ET LS7 in the works...
2005 Redline CTS-V stock?!?!
12.97 @ 112.90 2.36 60'
I only have 1 spare rear end...
:wtf:
so I couldn't open the hood 
