[s-cars] S-car head repair

[Charlie Smith]

Earlier, Tom Mullane wrote:
>
> It sounds to me like the two visibly bent valves were damaged when the car
> was not running.  The belt was off, so the cam was fixed and crank was
> moved. Two open valves were damaged.  Running the engine probably resulted
> in some additional contact between the pistons, the town bent valves and the
> head, but the other valves should not have been touched.
>
> Take the offer, fix the car, and get on with your life.  The last thing I
> would want, if I were you, is to have them start removing pistons.  This is
> not a race car; a couple of marks on the top of a piston or two should not
> affect the drivability or life of the car.

Tom -

I can tell you from personal observation, valves touching the pistons
like this can cause the top ring groove in the piston to get 'squished'
and thus tighten up on the top piston ring.  The ring won't seal and
will end up breaking, causing score marks on the cylinder wall.  This type
of valve to piston impact can also cause cracks in the piston, which can
lead to the piston breaking apart.

Also, if the valve head is bent, it has caused the valve stem to bend
into an "S" shape.  When this "S" shaped valve stem enters the valve
guide, it will probably screw up the valve guide.  I have seen valve
guide inserts split from this cause, and I have seen cracks in the head
when the guide holes are bored directly into the head.

    - Charlie


  Charlie Smith   charlie at elektro.cmhnet.org  614-471-1418
  http://www.elektro.com/~charlie      Columbus Ohio   USA
  http://www.elektro.com/~audi     photos & technical info

  95 S6 Quattro  -  24 PSI, RS2 6 speed, and other features
  97 Dodge Ram   -  35 PSI, 4x4 w/Cummins turbo diesel