A week ago I bought a 78 model F150 with a 400 and found
out today that two of the spark plug threads in one head
are stripped completely out. I don't see how the plugs stay in the head with the engine running, but they do.
Is there a way to fix the threads, or do I need to find a new head?

Thanks,

Phil

 

You can buy a helicoil tool and repair the heads. It is recommended that the heads be off the engine to install the helicoils. It is possible to do it with the heads on if you are very careful. If you remove the heads, I would take them to a machine shop to have them installed, or just plain get some new heads and rebuild them.

 

Thanks for the reply Eric.
If I choose to try the helicoil method with the heads on, how big of a chance am I taking with getting small pieces of metal in places where it shouldn't be. In places like between the top of the piston and cylinder wall, or even possibly embedded in the top of the piston, once the engine is started again.
Maybe I will get lucky and it will blow any foreign matter out the exhaust port?
Maybe I should start looking for a set of heads.

Thanks,
Phil

 

I recently did a job on an aluminum head with it on the engine. I smeared thick sticky grease on the tap tool and let the grease catch the chips. I would run it in a few turns, pull it out and clean it, regrease, and run it in some more. The job turned out well, but I won't know if I dropped any chips in bad places until the engine comes apart some time in the future.

I wish they made the tap with a hole in it for a magnet so it would hold the iron chips better. On an iron head you can always slip in a tiny magnet also.

 

Thanks for the tips, I think I will try it and see what happens,
Phil

 

Also you can call around your local auto machine shops. Some have a special tool for the exact problem you have. A shop did a job for me with the head still in and luckily it was on a cyclinder that the guy could work on and get bot arms in there. The tool had two little hook picks on it with a vacuum line that you need both arms in there to operate. He picked off a half a thread at a time and the vacuum hose sucked each one up. You dont want to drop any piece of metal down the the head it'll kill the walls.