Spark plug blew out - help

[4runnernz]

So was driving my 1994 4runner and suddenly the car starting making a strange flapping noise, the power dropped considerably as well. Took it to a local shop and he first said I had an issue with the exhaust manifold. On closer inspection he told me that the spark plug had blown out. Some previous owners had rebuilt the head and had made the spark plug hole too big, the mechanic said he couldn't fit a new spark plug in there and that he would have to replace the head ($300 for parts and 400-500 in labour) he said it needed an "oversized" adaptor so that a spark plug would fit in, and he had tried calling around to no avail. Now the part he is talking about surely costs no more than a few dollars, so it would be preferable to take this route.

Firstly I guess just wondering if anyone had similar problems, or new if this would be an adequate fix? And secondly if it comes down to replacing the head, is this an accurate price I am being quoted.

 

[junkyardbiker]

Find a better mechanic/machinist. A helicoil or a kingsert thread repair insert job will only cost you a fraction of that and and be just as good as new. Available at any Autozone, you can do it your self. Just use grease liberally in and around the hole to catch the metal shavings and keep them from going into the cylinder. If you were in my area I have all the best goodies for this stuff.

 

[4runnernz]

Yeah I was looking around and it looked like the helicoil was a fix people were doing in similar instances. The mechanic said that if we could find the part then he would do it, so maybe if I go back to him with the helicoil fix he will do it. When it comes to purchasing the helicoil are there a range of sizes that I should be aware of?

 

[KidVermicious]

When it comes to purchasing the helicoil are there a range of sizes that I should be aware of?

Yup. You want a helicoil insert that matches the thread on your spark plug.

And if you're not going to do it yourself, take it to somebody else - don't take it back to the mechanic you already talked to. He's worthless if he doesn't have a box or helicoils or timeserts on the shelf, he's lazy if he can't call up NAPA and get a helicoil set sent to him on the next truck, and he's downright shady for suggesting that you replace the head.

 

[4runnernz]

Is it at all possible that the hole is too big to fit a helicoil?

 

[KidVermicious]

Is it at all possible that the hole is too big to fit a helicoil?

I suppose if they already coiled it once and then it blew again, it could be too big. If that were the case I'd check out Timeserts, I think they have an oversize spark plug hole repair kit for exactly that situation.

If a Helicoil or Timesert is installed properly though, it's stronger than the original threads in these aluminum heads.