Plug blew out of head last night

Yep, like the title says, #4 plug blew out of the head last night on my way home. The neighbors sure looked at me kinda funny as I pulled into the driveway...

The backstory is that when I changed the plugs for the first time about year or so ago, I noticed that the #4 plug hole was stripped by a PO, so I had a guy put in a steel insert. The plug, and the insert, blew out last night.

As I'll be putting a new head on, are there any suggestions for a not-stock head?

I've never really researched heads for the LS1 before, as I didn't ever think I'd be needing new ones.

The car is a daily driver and will only be used on the street, but if there are some gains to be made that will keep the car a reasonable street car, I'm interested to hear suggestions!

Best,

Andy

I think 799 or 243 castings are desirable.

Arthropraxis wrote:I think 799 or 243 castings are desirable.

Thanks Anthro, I spent a couple hours today googling around, and those are good castings.

Funny, as I was driving before the plug blew out I noticed a ticking sound coming from the engine. I thought it was a noisy valve or something, although it bugged me that it would just start being noisy like that. What would cause it to happen so fast like that?

Anyway, I just found this on a website discussing repairing stripped plug holes that explains what the sound really was:

When the threads are about to come loose there is often a slight ticking sound/noise, like a small "exhaust manifold leak" would sound.

I guess that explains it!

Andy

I blew a plug in a Volkswagen and it was sudden like yours. Made an awful racquet going down a quiet German village road at 2am. You may as well put in a better cam to take advantage of the increased air flow, wouldn't be too much more work.

Weird, but good news.

I checked the plug this AM in the daylight (it was dark when the plug blew the other night) and it turns out the insert did not blow out with the plug, just the plug came out.

I just now simply put the plug back in and the car started up fine.

Is it possible that engine vibrations rotated the plug out?

It seems hard to believe that could happen.

I'll pick up a new plug on the way to work, maybe there is something messed up on the threads of the plug itself.

Andy

Interesting problem. With that steel insert, perhaps heating/cooling cycles are loosening the plug. Are you using an anti-seize compound in there? I'm not sure you should, just asking. I had a plug come out of a Mazda aluminum head, what a racket. I just re-torque things and it was fine.

Rich

Strange that the plug would twist out of the head and the spark plug boot. My boots hold on to plugs pretty tightly; even with a dab of dielectric grease. I would just re-torque it to 15 ft/lbs and see if it happens again. Maybe when the insert was installed, the plug was barely snugged up due to fear of re-stripping?   

Yeah, the sparkplug boot is pretty darn tight on the end of the plug plug, I can't see how the plug could have screwed itself out.

I think the plug blew out of the insert.

I wonder if the ID of the insert is slightly too big or something?

Andy

acorad wrote:I think the plug blew out of the insert.

I wonder if the ID of the insert is slightly too big or something?

AH! Wow. I see what you mean. Well, atleast you have great compression eh!