jimcanoe 0 Posted June 26, 2010 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 Share this post Link to post Share on other sites
MowerMechanic 0 Posted June 26, 2010 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. Share this post Link to post Share on other sites
dentwizz 6 Posted June 26, 2010 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. Share this post Link to post Share on other sites
Al 6 Posted June 26, 2010 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 Share this post Link to post Share on other sites
sammiefish 2 Posted June 26, 2010 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 Share this post Link to post Share on other sites
Willy 2 Posted June 26, 2010 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. Share this post Link to post Share on other sites
jimcanoe 0 Posted June 27, 2010 Thanks for the great input. Jim Share this post Link to post Share on other sites
Burntime 1 Posted June 27, 2010 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... Share this post Link to post Share on other sites
Storm7012 0 Posted June 27, 2010 You didn't say what engine this is? Share this post Link to post Share on other sites