You can set the head on its side and fill the ports with mineral spirits etc, and see if the valves are leaking. A flat steel plate with an air chuck welded in over the bore also works well for checking leakdown with the head off.
If it is indeed blowing down by the piston, there may be land or skirt damage. As the piston is forced up with the rope packing, it would tend to cock in the bore as the rope was compressed between the side of the piston top and the squish area flat part of the head. Whether this side load would be sufficient to collapse anything... I dunno... with enough force, something is going to fail
I do know that at speed when there is metal contact, it makes a real mess; but in this case it's obviously a load issue only...
Glen
--Previous Message--
: No new thread and no pictures yet.
:
: Our findings... totally inconclusive.
: There were no obvious hole or broken
: bits of piston, no broken head studs,
: nothing. We also cleaned the top of
: piston #4 and looked for cracks and
: other problems that might have been
: hidden by the carbon deposits. Nothing
: there either. All I can figure is that
: somehow I put enough torque on the
: engine to unseat the head gasket for
: #4. There is an oil drain passaged
: parallel to the bore that runs very
: close to the sealing rings for the head
: gasket.
:
: I have done a cursory cleaning of the
: head. My plan at this point is to take
: the head to the machine shop and have
: them crack and leak check it and maybe
: even go ahead and have the valve seats
: recut if nothing is found wrong.
:
: When I know the head is good I will
: probably fit it temporarily to the
: block with an o-ring in place of a head
: gasket and repeat the leak down test.
:
: More to follow.
:
: Doug L.
:
:
: --Previous Message--
: Doug I can feel your pain. I have been
: working on Brit iron for a long time,
: and many times I have put my plan into
: action before thinking it all the way
: through, resulting in broken stuff.
: My mantra that I repeat before I do
: anything is "OK now how can I
: screw this up". Really.
: I'm visualizing #4 packed with light
: rope, with a TON (???) of torque
: applied, what's the weak link? I dunno,
: I've given it a lot of thought and
: can't come up with anything good. The
: head "squish" area is a
: little thin if it has been resurfaced a
: lot.
: In any case, if it makes you feel
: better, everybody screws up sometimes,
: fewer admit it.
: This definitely warrants pictures!
: Hang in there,
: Glen
:
:
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