I don’t think this is a good solution

April 1, 2012 | By Richard Prince


While looking for information on tools, I came across an article about repairing blown-out spark plugs on late model aluminum head Ford cars and trucks. I was shocked to learn that this problem is fairly common. This is another reason to keep my older cars running. It seems that the plugs can blow out of the engine when the threads give way. Apparently there are better solutions than a very expensive head replacement. It seems that one of the costs is just getting to the head to get it off. On some vehicles, the best solution is to actually remove the vehicle’s cab. Think about the shop costs for that.

Heli-Coil inserts can be used, but they are not always successful because of the thinness of the insert. The article explains that the Calvan 38900 Specialty Tool Kit has a much thicker insert that can be used when other thinner repairs like the Heli-Coil have failed to hold. The beauty of the Calvan is that it is actually stronger than the original threads. And if a HeliCoil fails, this insert can still be installed. The article includes a link about removing existing Heli-coil inserts. If I had one of these engines, say for retrofitting in a modified car, or had one that needed rebuilding, I would insist on using the Calvan inserts on all plugs as a precaution.


I read through the article and something that makes me a little bit uncomfortable is this: “...drilling is done with your air ratchet and the drilling tool included in the kit. It is recommended by Calvan to use a fiber optic bore scope to insure metal shavings are all removed from the cylinder. The debris is removed by using a blower with a small diameter rubber hose.”

In a nutshell, in order to install the Calvan thread insert the damaged spark plug hole has to be drilled and tapped with new threads that are sized to accept the steel Calvan thread insert. When the spark plug hole is drilled and tapped aluminum debris will inevitably go into the cylinder and I’m not convinced that using a blower with a small diameter rubber hose will remove all of the aluminum bits from the engine. In fact, I believe that it will be extremely difficult to remove every single shard of aluminum without removing the cylinder head.

So, installing thread inserts in any aluminum cylinder heads, including those from Ford, as a preventative measure when an engine is being built is almost always a good idea and doesn’t present the potential problem of bits of metal being left behind in the cylinder, but installing the inserts in an assembled engine worries me because I don’t think it’s feasible to completely clean the metal out of the engine without removing the head.