The other day I went to change my oil and plugs, but one of the
  plugs had seized and getting it out really did a number on the
  threads in the housing and cam out with several of the deepest
  threads caked with aluminum.

  I went and got a tap and helicoil kit...

  I re-tapped the threads and the new spark plug seems now to fit
  fine and snug up OK, but I am a little worried about all the
  damage that must have been done. I am now trying to decide
  which is the lesser of two evils. Leaving the threads as is if
  the spark plug can get torqued to spec, VS. installing the heli
  coil and possibly getting aluminum shavings into the combustion
  chamber. I would stuff it with grease soaked rags, but there is
  always a concern. Up sizing the hole for the heli coil will
  make a LOT of shavings.

  My though is that if the threads can tolerate the proper torque,
  then they should be good to go.

  Opinions?

  Does anyone know the proper torque on the spark plugs?
  --
  David Leonard

  Turbo Rotary RV-6 N4VY
  http://N4VY.RotaryRoster.net
  http://RotaryRoster.net

  http://www.ngksparkplugs.com/techinfo/spark_plugs/installation.asp

  The engine should survive a few aluminum shavings. They should
  melt the first time it fires. No guaranty :)

  Use a grease soaked string.

  I would pump (with a grease gun) the top dead chamber full of
  Vaseline before you started drilling and tapping. Then rotate it
  around to the exhaust port and dig the Vaseline with the chips out
  from there.
  Then flush it with auto TX oil.

  Paul Lamar

  I'm sending spark plug torquing instructions recently posted by
Lynn  Hanover. Hope it is of some help.

  Mark

  Now tighten the new plug into a scrap housing, or your wife's
  Honda to 14 foot pounds and then back out. This to flatten the sealing
  washer.
  Then wipe on just a hint of Nickel anti-seize on the threads. Nothing
  within 1/4" of the tip. Practice torqueing to 10 pounds with
  extension sticking through between your middle and ring fingers.
  Torque a plug into a scrap housing to 9 pounds, then turn it by
hand  to what you think is 10 pounds. Then check the plug with the
 wrench set at 11 pounds. The plug should turn a bit to get to 11 pounds.
  Get a feel for 10 pounds using your wrist only. 10 pounds with
  lube is plenty. After a few installations the anti-seize will have
  been spread all the way to the inside end of the plug hole. Great heat
  conductivity. Plugs will never lock up in the hole. Threads will
  last as long as the housing.

  Always use a torque wrench. But if none is available you can do
  the ring finger trick and get 10 pounds every time. Only you
  tighten plugs, not your ham fisted brother in law.

  Lyn Hannover

  For a plug torque chart, go to;
  www.championsparkpluds.com/charglossary.asp
  <http://www.championsparkpluds.com/charglossary.asp

  Plugs can also be tightened properly without a torque wrench. For
  new plugs or
  with a new gasket I think it is 1/8 turn from finger tight. If
  reusing the
  gasket, 1/16 turn from finger tight. You need to be sure the plug
  is contacting the gasket surface of the housing at finger tight. Never
  seize on
  the threads. If it wants to turn more than prescribed without
  snugging up, it
  was not on the gasket surface. Taper seat is 1/16 turn from finger
  tight.

  Dale Davies

  First, DO NOT USE A HELICOIL! Sorry to shout but helicoiling spark
  plugs has always been a bad thing to do. The helicoil partially
  insulates the plug and that can require you to use a colder plug.
  The best insert you can use for the plug hole repair is called a "Time
  Sert". Made by the Time fastener Company they are the best inserts
  you can buy, period. Search Time Sert on the web to find their
  site. The plug inserts are steel but they are copper plated to
  insure proper heat transfer. Look them up you will be glad you did.
  I won't use anything else now. Bill Jepson

  Still have your RV10 Kit Bill?

  Paul Lamar

  Hi Bill,
  It's funny that you feel so strongly about Time Sert. I did know of
  them from my search, but most people seemed to weakly recommend the
  heli-coil. As far as heat transfer, it does not make much sense to
  me that a alum-copper-steel-copper-alum interface should
necessarily  do any better than alum-steel-alum... no matter though,
because it  is easy to start using cooler plugs if needed.

  I liked the idea of a coil as a means of taking up any slop and
  preventing any breakage. Lastly, Todd Archer told me about some
  certified aircraft engine that comes new with helicoils.

  That being said, it is not too late for me to switch. I taped out
  the hole today and feel confident that I got out all themetal
chips big  enough to do any harm. But when inserting the coil it mis-
threaded and  had to be removed, which destroyed it. So now I still
have my choice.

  At the auto parts store there was an insert that appeared to be black
  anodized alloy, or the heli-coil (both labeled as generic inserts)
does  that sound like the Time Sert? Do you think the threads are going
  to be the same for the two?

  --
  David Leonard

  Turbo Rotary RV-6 N4VY
  http://N4VY.RotaryRoster.net
  http://RotaryRoster.net

  There is another style thread insert, but I do not recommend it of
spark  plugs. The name is Keensert and the OD is bigger than
Helicoil. They use  regular taps, a slightly larger drill than would
be standard for  that tap and  have lock pins you tap down wwhen it
is installed to lock it in so  it can not  come out. Great for bolts
in Aluminum heads and intake manifolds.

  If the outside thread on the timesert has a different thread, I
  would try
  running the tap for the Helicoil in again to clean it up. The coils
  are a bit
  tricky to start into the thread. A bit of gentle wiggling usually
  does the
  trick. Also use the proper installer tool.

  Dale Davies

David,
The difference in the Time Sert is that the insert is solid, not coiled.
Yes as a mechanical engineer I can tell you that many threads in soft
metal,(aluminum or magnesium) are factory inserted. Nobody does spark
plug holes for the factory. I will also say this Dave, if you get a
"weak suggestion to use a helicoil" the guy telling you NEVER used a
Time Sert. I worked for Kawasaki in the late 70s. They were looking for
inserts to recommend to their dealers. The Time Sert was selected and
Kawasaki wouldn't use anything else. They used to sell them through
their dealer network. It has been ages though so I don't know if they
still do. These are NOT keenserts which are huge and clunky, and require
a much larger thread. I'll check for you if you can't find them. BTW
all the domestic car manufacturers now use time serts. Bill Jepson


Considering the Timesert uses the same tap as a Helicoil, I would go with it.
Being swaged into the aluminum, would also help heat transfer while locking it
into place.

Dale Davies