"Paul" wrote in message ...
I did the pressure test today. Filled the engine with water, closed the
cooling system and eliminated manifolds from the loop. Then applied 20 psi
pressure to the cooling system (water jacket). It held easily for 20 min. no
change (twice). The pressure dropped sligthly when I was cranking the engine
with plugs out while keeping cooling sys. pressurized.. Spoke with a local
rebuilder that suggested the above while canking the engine and watching for
water appearing in cylinders (coming out of plug sockets), crankcase or
elsewhere. Drained the oil and watched for water dripping from underneath.
Nada. Filled both manifolds (with raisers) with water to look for leaks.
None. I guess that I got to check them under pressure.
In summary, no obvious leaks. There may be some (tiny) there that might show
if the engine is warm. That would be my next step I guess. As advised here I
built a tool for pressure testing using a piece of plastic 3/4 inch pipe,
plastic screw-on cap and a tire valve that I installed in a cap. Worked
great. Used a small compressor (tire type) to apply pressure and since its
gauge was constanlty showing pressure changes I knew exactly what's
happening. Despite that there's no pregress locating the leak. Any ideas?

Years ago in Popular Mechanics or Mechanix Illustrated there was an
auto repair genius who had monthly stories that solved conundrums such
as yours. In one story he described a pressure testing device where he
broke the porcelan off an old spark plug and brazed a tire valve onto
it. He would screw it into a cylinder and put some air to it and #1,
listen at the exhaust pipe for leaky exhaust valves, #2,listen in the
carburator for leaky intake valves, #3, listen at the crankase
breather tube for leaky rings, #4, look in the radiator for bubbles
indicating a bad head gasket.I don't know if this would help you at
all but from what I can follow in this saga of your's you've only
applied 20# of pressure to the cooling system "in general" to the
outside of the cylinders and maybe if you can apply 100#+ pressure to
each cylinder "specifically" from the inside it might narrow down your
search as to "where" the problem is and might give some clue as to
"what" the problem is. If you ever do find out what the problem is, be
sure to post it.