Miata Mailing List: October 1993, Message #215
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   From: meek@me.mech.utah.edu
Subject: Re: Head R&R
   Date: Fri, 22 Oct 1993 11:23:15 -0400

>> There's a process the name of which I've  
>> forgotten that a machine shop can do (the next generation Helicoil,  
>> as I understand) to fix it.
>> 
>> Now the problem is, this isn't a good thing to do with the head on  
>> the car -- something about metal filings dropping in the cylinder --  

>Well... you could always use a magnetic drill bit to drill out the hole. 
>I've done it, but it was on a 1972 Honda 600 Sedan - that engine was so
>noisy I probably wouldn't have noticed a dropped valve.

This won't work.  The heads are Al-Mg alloy, i.e. non-magnetic.  I have
known of people plugging under the hole to prevent chips from going in. 
But to be sure that nothing fell in, it is best to remove the heads.

About removing the heads.  Getting them off is relatively easy.  It's
putting them back on is where you have to be careful.  You need to, of
course, replace all of the gaskets (fairly cheap and easy), torque the head
bolts properly (not too hard), and reinstall the cam shafts and time the
valves (pain in rear).  After you have driven the car for a few hundred
miles you should re-torque the heads which will involve removeing the cams
and then re-installing them.

You might see if you can save some money by doing part of the work like the
removal and reinstallation and let the shop re-do the cams and valves and
you out the rest of the external junk on (hoses, wires, etc.).

Good luck  (you'll need it)

Sandy

Sanford Meek
meek@me.mech.utah.edu