<snip>
>When revving the engine to 3 or 4k or so, as in
>accelerating through the gears, AS IT IS REVVING DOWN it sounds like someone
>suspended a pushrod from either end with a bunch of washers threaded on it,
>and it is vibrating and ringing. It is only as the rpm are dropping that it
>happens. The engine is still running fine and I just did a valve adjustment
Sounds a bit like rod knock. I'd be inclined to pull the oil pan and
ckeck for a loose rod. Perhaps check the torque on the end-caps.
>Other hints; at idle (c. 800 rpm), after it has warmed up, it will SLOWLY
>drop rpm until it wants to cut out, as if there is a vacuum leak (I'm sure
>there is and I've been blowing it off until the head replacement);
Sounds like a vacuum leak to me also. I've got one of those hand
operated vacuum pumps which has a gauge. I use that to check the engine
vacuum while the engine is running. I would not entirely rule out a lean
mixture though... A common place for a vacuum leak is the diaphram on
the distributor. Also check to make sure the manifold and carbs are all
tight.
Good luck,
John Van Valkenburgh KE4QBR
Raleigh, NC
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