<VV> Zero Compression

[Tony Underwood]

At 07:55 hours 07/05/2004 -0400, Sam & Marissa Andolino wrote:
>On the way to the Concours qualifications, we lost 1,3 5 cylinders on our 66
>Turbo.  Different people were thinking stuck intake valve.  Before taking
>the head off the number 1 cylinder had zero  compression 3 and 5 had about
>120 lbs each.   The head shows no sign of a problem and the piston has no
>hole in it.  The question is, what could cause this to happen in such a
>short amount time?  The engine has a little over 100,000 miles.  We were
>thinking about having the engine rebuilt by having the heads checked/rebuilt
>and putting in new pistons and rings.  We would like to cover all the bases
>before putting the engine back together.  Any ideas would be appreciated.
>



It's not terribly unusual for a valve seat to come out, dance around a bit
and then reseat itself when it lands "just right" in the pocket.   This
doesn't mean it slips exactly back into the pocket... usually it will
remain cocked slightly and "look OK" but still leak.    Been there done
that.   

Pull the head down and check the seats closely and see if any of them are
loose or show signs of having caused any extrusions or imprinting around
their respective pockets.    Next, check the valve guides *Closely*.  Worn
guides contribute to loosened seats.    

Meanwhile... if you  were going to have the engine rebuilt (a real rebuild
or an overhaul?  There's a difference) it would go without saying that the
heads would be rebuilt as well.   If what you intend to do is an overhaul
(usually rings, maybe pistons, bearings, gaskets/seals and a valve job) be
sure to stress to the jobber doing the heads to make sure the seats are all
OK and replace any (maybe ALL) if there appears to be any doubt about them.
  Usually most careful people will replace them all or either pin  and
stake them to make sure they don't come out.   Really careful people will
install deep seats or pin and stake the new replacement seats, just in
case.      


Good luck, 


tony..