So i stripped 1 thread on the head because i over torqued a sparkplug. So i had to helicoil it and problem solved. My question is how much power can it withstand? The car isnt pushed hard but i like to drive it hard once in a while. Can it hold up to 500whp?

 

When done correctly, helicoils are stronger than the original aluminum thread.

 

^ It's true.

 

i had a F150 that i helicoiled twice. (apparently the 5.4 aluminum heads are weak) but they both held up good, when done correctly. Are you going to be pulling the head? if not make sure you put some grease on the tap and only go a few turns before pulling back out. The grease will prevent the metal shavings to fall in your motor (if leaving the head on)

Granted my F150 didn't have 500hp.. haha

 

Well the only problem with a heli-coil is they tend to come back out of the head when you take out the spark plug. You actually need a Time-Sert they are the correct repair for a spark plug they will stay in the head and be stronger then the orginal.

http://www.threadkits.com/time-sert/...lugs/kits.html

as for 5.4l they make a bunch of spark plug repair kits because almost every f150 goes through the same issue.

 

^ +1

I have used Time-Serts or similar in small displacement 2 cycle engines and they have held up for years in racing condition.

GL with your project.

 

Heavy duty Keenserts.

 

What helicoil kit do I buy? Is there different thread pitch?

 

You purchase according to your spark plug thread. That will be your I.D. Your O.D. will be whatever they suggest. will specify a drill size and tap size.

I think our plugs have a M14 x 1.25mm or 1.5mm pitch thread. I can't find a 1.25mm listed for a 14mm diameter in the metric fine chart, so it might be a 1.5mm pitch.


http://www.sjdiscounttools.com/hel5544-14.html


Over tightening will not cause one thread to strip, it can stretch and eventually strip all the threads. So verify that this is in fact the problem.
If it's one thread, it sounds like a cross-thread issue. I would buy a tap and chase the threads if you're having trouble threading the plug.
If the plug threads in just fine and only one thread is boogered, I'd roll with it. I don't think it would hurt anything. Those things thread pretty deep.

 

+1 for time-serts

Used them many times in Aircraft engine overhauls.

 

I've used heli coils on all of both heads of my lightning after I build the motor, and added a Kenny bell blower. The modular Ford motor doesn't have to many treads in the plug holes! It's a known problem with the 4.6 , 5.4.... Don't know about the V 10?? after I felt as if it changed my heat range on the plugs....reason I did all eight banks!