Ignition: Spark Plug Failure?

[fargoguy]

So this morning i drove my 61 lark (OHV 6) to work, as i'm getting it ready to go on the Prairie overdrive this weekend in alberta. After i got onto the highway, i got it into OD, it sounded like it had a little knock or something in the engine under load. I kicked it back down, noise was not evident at higher RPMs. Then it started missing heavily, and there was a loud pop under the hood and lots of noise- shut it down, coasted to a stop and checked- thought i'd thrown a rod??? Turns out in cyl 6, all that was left in the spark plug hole was the metal piece of the spark plug, the porcelain and the electrode were gone, not even in the plug wire. A coworker came by, we towed it the 2 miles back home. I quickly took out the metal piece, and checked the compression on that hole- still have 130lbs compression. i found a piece of the plug porcelain in the wires near the starter solenoid on the inner fender. My question is- what could have caused this? Is it a simple case of spark plug failure? Ive never seen that before, but its possible. It will get 6 new spark plugs tonight for sure and we'll see how it runs then, but i'm more worried about it happening again? I appreciate your opinions as I had plans to leave for a 1400 mile trip this weekend. Thanks in advance. Evan

[dickeedee]

welcome to the nasty hand of Fate..
It happens pretty rarely, but it happens...
It's a defect in the plug,
replace all 6 , I'll bet you a Tim's it'll never happen again...unless it's Motomaster..lol...

[DEEPNHOCK]

Springtime can be a weird time of year.
Warm during the day. Cold at night.
Here's a swag...
Condensation formed on the outside of the porcelain on the plug and dripped down to the metal part of the plug.
A hard frost caused the water to freeze and a teeny crack started in the porcelain.
Then, due to several hot/cold cycles, the porcelain cracked and the center of the plug failed and shot out.

A failure analysis committee could be formed, and engineers could analyze your lifestyle, driving style, fuel habits, etc.
Or...
You could change the set of spark plugs and drive with impunity!
HTIH
Jeff

[41 Frank]

When I was racing stock cars years ago this problem of the porcelain blowing out of the plug used to happen quite frequently to those of us using Champion plugs. We changed to Autolite and never had any more problems.

[63 R2 Hawk]

Back "in the day", I had a '55 F*rd with a mildly "hopped up" motor, including a Mallory dual point distributor and Mallory coil. I can remember at least two occasions when I blew the porcelain out of the plug body. I had so much ignition timing advance that I had to install a kill switch for the coil so I could start cranking the motor without spark to get some momentum going for the starter, otherwise starter would stall when the cylinders fired.... Ahhh, the Good Ol' Days, when premium gas was premium!

[fargoguy]

Springtime can be a weird time of year.
Warm during the day. Cold at night.
Here's a swag...
Condensation formed on the outside of the porcelain on the plug and dripped down to the metal part of the plug.
A hard frost caused the water to freeze and a teeny crack started in the porcelain.
Then, due to several hot/cold cycles, the porcelain cracked and the center of the plug failed and shot out.

A failure analysis committee could be formed, and engineers could analyze your lifestyle, driving style, fuel habits, etc.
Or...
You could change the set of spark plugs and drive with impunity!
HTIH
Jeff

i will choose to drive with impunity! Thanks guys for the responses. Evan

[jackb]

I think Jeff's got it...