Well, Jim....
that's what usually happens when an idling
motor overheats. Parts swell, friction goes
up, temp goes up, induction air temp goes
up, and the engine becomes a "heat sink"....
hear a "marble-like" noise when it "shuddered"? If so, that would be
pre-ignition/detonation (sorta like spontaneous
combustion).
This is to be avoided. One should perform
a pre-cautionary engine shutdown under
these circumstances to prevent
possible engine damage (blown head gasket, warped head, loss of ring tension,
etc.) from occurring.
If it was 90F+ out there, and you're running
one of the old two-blade (or even four blade) metal fans, I can see this
possibly
happening. Today we have the later, upgraded mult-bladed fans which move a
helluvalot more air, though it may be more
of an internal cooling system problem rather than an air supply problem, Jim.
Something needs attention for certain
though, and before the warm weather gets
here for sure.
Cap'n Bob
'60 Frog
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