<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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