stripped plug threads

i just started changing spark plugs and discovered i have 3 holes stripped out.the new plugs threaded in on 1 & 2 but drop right in om #3 & 4 ,then i stopped. this is way over my head now. will i need a new head?
mike

A machine shop can repair the head using helicoils, in all likelihood. However, to do that repair, the head will have to be taken off the engine.

Actually it's pretty hard to strip the threads in the head. Are you SURE they are stripped, or are the threads filled with some crud that prevents threading the plug into the hole?

no crud in the way. they drop down in the hole freely.
i'm almost tempted to just buy a head.

Stupid question but I've gotta ask...

Are all your plugs the right ones? All same part number?

Yeah that is weird that you stripped the threads in a cast iron head. I stripped the threads in an aluminum head on a Mazda once and had to take the head off and have a machine shop put some helicoils in it. An expensive lesson on proper torqueing of spark plugs.

So did the old plugs thread out fine?

they are all the same 4428 bosch.
i just put it on a flatbed. i dont know if heli coils will work.the jeep service guy said they would try. i think they will tell me i need a head.
mike

I agree, I think you should check that the plugs are right. I mean, if you stripped three holes in a cast-iron head so badly that the plugs fall in, you ought to know it! Usually a stripped thread will still catch on the way down and then not hold when you tighten it; it won't allow the plug to fall through unless we're looking at the aftermath of a titanic struggle to get the old plugs out.

the old plugs were super tight. but they did seem to thread out.i put 150 halogen light on it to make sure i could really see,i 'm getting blind. i bought this from a dealer that got it at an auction,so i dont know who to track down and beat with a baseball bat.what sux is a just ordered a load of offroad stuff online and BAMM..murphys law.
mike

thanx for the replies. just picked er up and she is idling smooooooooth.
fwiw,there is a new gimmick out that'll re
thread them stripped holes from the bottom up?!.i wound up getting 2 retaps/heli,he cleaned up the other threads,called me and suggested i NOT use the bosch 4+ on a 2000 because they dick with the computer. i told him to use whatever plugs he wants cuz he'll be doing them next time.they also did the recall on the manifold (fires),cleaned up my cables.it really seems there was a lot of pride in the work. the repair with plugs ,labor and tow was $340 ,thats still lower than a monthly pmnt -i'm better now.
mike

it still pisses me off.