how often do spark plugs break off into a cylinder head?

a friend of mine and i have been arguing about this for (literally) years. he stubbornly refuses to change the plugs on his '95 LT1 Formula with 70k on the clock because he's SURE he's going to break off a spark plug in the head. in a previous life, he apparently had many a bad experience with aluminum heads and breaking spark plugs.

i think he is absolutely insane. am i right??

-Brian

I've been a gearhead, working on all sorts of cars - domestic and foreign - for more than 50 years. I have NEVER seen a spark plug break off.

Well, if antiseize was used during plug installation, then he shouldn't be overly concerned.

Careless work or crappy tools can increase the chances of a broken plug, stripped threads, etc on these LT1s.

If he fears he will break a plug at 70k, the chances of a broken plug will only increase over the miles and years all things considered. What's his plan; to leave them in indefinitely?

The porcelain can/will break off quite easily, actually ;). I even f'd up one time INSTALLING a set of plugs into my old winter beater, put a little too much angle on the socket when I was snugging up the plugs, and just 'cracked' the porcelain :rolleyes:.

However, BREAKING the plug off in the head is damn near impossible :think:. I think the real (legitimate) fear though is stripping the threads from the head when pulling the plug out. If it has any heavy corrosion build up, and the threads start to pile up when you're pulling out a plug, you CAN do enough damage to the threads/head. It's repairable, but a P.I.T.A. "IF" you feel a plug start to tighten up badly while taking it out, reverse the ratchet (or just wrench the other way ;)) and screw it back in. Then work it out gently, rocking back and forth on the same spot every ~1/2 turn or so.

BUT, that's only IF you have a problem. Not normally that common. I did, however, have an exhaust stud break off in the head of my Camaro when I was pulling the factory exhaust to install the headers :(. I didn't realize there was a problem until it was too late :rolleyes:.

usualy you would strip the threads instaling plugs.. but having anything break off into the engine seems almost impossible... ive never heard of it happening.

Out of the 20+ years working on engines, I have only broken the porcelain tip off once, but that was on a lawn mower.....:)

I my 93Z, changed plugs 4 times, no probs......

We broke the tops off 3 of 8 from my car, but we could still unbolt em.

I know what he is talking about.
Does he drive his car in the snow?
If not then he should be fine.
On the older steal headed cars this happened quite often, especially if its in a plow truck.
The aluminum headed were not quite as bad.
The winter salt turns everything to rot. After a few years the plugs rust/sieze in place.
He should be fine, I am from Buffalo, NY, my brother had a shop and I saw everything imaginable when it comes to rust and rot. An accetelene torch AKA heat wrench is your friend when it comes to rusty bolts in NY.
Make a bet with him. Bet him $150.00 if you get the plugs out without breaking one inside, he pays you. If you do break one off then you fix it on your coin.
Tell him to get his wallet ready ;)

YES spark plugs can break in an aluminum head!!! It has happend to me on a bike. I have picture proof :p

http://www.cb1100f.net/modules/coppermine/albums/userpics/valves.JPG