spark plug blew out

[jimcanoe 0]

While running just fine the spark plug blew out of the cylinder head ruining the threads in the head. What would cause this to happen and should I just get a new cylinder head? Thanks, Jim

[MowerMechanic 0]

if it is a flat head then yes your easiest option is a new head. You can Helicoil but dont plan on it lasting. The only time i had this happen to me is when i put a machined down high compression head on my kohler 10 hp with an ethanol fuel mix and advanced the timing:O. My bet with yours is someone prior had cross threaded the plug when it was changed.

[dentwizz 1]

Actually if it is done precisely a Helicoil can be quite durable. Aircraft engines with aluminum heads actually come pre-helicoiled because they last longer. It is super critical that you get the hole drilled exactly to the right size.

[Al 2]

Hi, We put heli-coils in all the time. They are more durable than aluminum if installed properly. People tend to over tighten spark plugs. This damages the threads. Tighten the plug finger tight plus 1/4 turn. Josh is correct, items that are built to mil specs, do not have bolts screwed into aluminum threads. Either heli-coils or other thread inserts or captive nuts are used. Worked on this stuff for Rockwell International for 38 years. Al Eden Al Eden

[sammiefish 1]

listen to Al... get it helicoiled that is unless youve got another head just laying around... while you are at it have them flatten the surface for the gasket

[Willy 0]

NAPA sells a kit with a tap and helicoils. I don't remember how much it cost but it's cheaper then replacing the head.

[jimcanoe 0]

Thanks for the great input. Jim

[Burntime 0]

My neighbor had a helicoil put in his harley 10 years ago and it is still going strong. And its been from Wi to Colorado and back 2 or 3 times thru the mountains...

[Storm7012 0]

You didn't say what engine this is?