<VV> Oops - need advice

ricknorris at suddenlink.net ricknorris at suddenlink.net
Tue Mar 15 06:46:51 EDT 2011


I have broken spark plugs off at the threads in old and in some cases water logged engines. Also, if you get a good misalignment on the wrench they will break.
--
Rick Norris
#36 Sunoco Corvair
www.corvairalley.com 

---- RoboMan91324 at aol.com wrote: 
> Joe,
>  
> It is almost certain that you only broke off the ceramic part  of the.  I 
> find it hard to imagine the hex head breaking away or  rounding off before 
> the threads pull out of the head.  The aluminum is  usually the weakest link.  
> Did you actually break off the top including the  hex head?  Assuming the 
> hex head is still there, you should try to  remove the remainder with a six 
> point socket with a 1/2 Inch drive.  This  should give you better leverage.  
> If the engine runs, you should first try  to get it warm.  Obviously, the 
> engine will run rough with only five plugs  sparking.  The aluminum head will 
> expand a little more than the steel spark  plug when hot and may make it 
> easier to remove the plug.  Unfortunately,  you may end up stripping the 
> aluminum threads from the head no matter  what.
>  
> If the other plugs are still out of the heads, check the end  for signs of 
> carbon in the threads.  A common mistake is to use spark plugs  with 
> extended threads that will remain exposed inside the combustion chamber and  allow 
> carbon buildup there.  When you remove the sparkplug, the carbon will  
> interfere with the threads in the heads and could cause damage and difficulty  
> removing the plugs.  Use only plugs with the proper thread  length.
>  
> If the plug's hex head is gone, you will need to remove the  head.  A good 
> machine shop could remove the remainder of the spark plug but  you need to 
> make a decision based on cost of a new head vs. the cost of the  machine shop 
> including the probability of installing a helicoil (or other  brand) plug 
> insert.  If you use an incompetent machine  shop, you will probably end up 
> paying for their service plus a new head because  you will not be able to use 
> an insert.  If you buy a new head, make sure  you get the right part number. 
>  If memory serves me, the 1965 heads used  smaller diameter bolts for 
> attaching the sheet metal.  You can use a head  with the larger bolt holes but 
> you may need to punch or drill out the holes  in the sheet metal for the 
> larger bolts.  Also, visible bolts in the engine  compartment will have different 
> sizes for the two sides.  This is not  a big deal for some but a big deal 
> for others.
>  
> Lastly, a little general advice on how to tighten and loosen  spark plugs 
> as well as bolts, nuts, etc. for this and future work.   When you push or 
> pull on the end of a ratchet, you are creating the  intended rotational force 
> (primary torque) as well as unintended side  load and secondary torque.  The 
> primary torque is around the threaded axis  but the secondary torque will be 
> to the side (right angle) of the threaded  axis.  You have two lever arms 
> and are creating two torques.  One  is due to the length of the ratchet 
> handle from the bolt axis and the other is  the total length of the socket and 
> extensions from the threads to the ratchet  arm head.  The primary torque is 
> desirable but not the other forces.   In effect, you are both turning the 
> spark plug as well as both pushing  and bending it to one side.  If you use a 
> deep socket and especially  if you use an extension rod, side torque is 
> multiplied.  You should always  try to compensate for this.  When you push or 
> pull the end of the ratchet  or breaker bar, always use an equal and opposite 
> side force at the axis of  the socket/extension/bolt/spark plug where it 
> meets the ratchet.  The side  torque can easily break off the ceramic portion of 
> a spark plug, will increase  the torque required to loosen a bolt and could 
> easily give you an inaccurate  torque when trying to use a torque wrench.  
> Keep in mind that failing to  compensate for the side torque also creates 
> more stress on the socket as  well.  You are more likely to crack or deform a 
> socket with both axial  torque and side torque applied.  You are also more 
> likely to strip the  hex of a bolt/nut head.
>  
> Good luck,
>  
> Doc


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