Posted by Bob Stopka on Saturday, July 26, 2003 at 9:06AM :
Looking for advice as to the cause. My 61 WM300 With had a terrible vacume leak problem preventing it from idling unless the choke was half closed, which would then cause
it to run very rich. It would only idle if the choke was half closed. If I opened the
choke all the way, at idle, it would stall right out. Manifold planed, new gaskets,
new carb, no vacume leaks that we could find. I gave up and brought it in to a local guy who is good with old engines. What he found was that there was a whole lot of vacume suction into the crankcase at the
oil fill pipe. This truck has the quasi
pcv for the time. Pipe from manifold to the
passenger side rear of block, and a rubber hose from the oil fil pipe back over to the oil filled air cleaner. The mechanic fixed the problem by restricting the vacume
sucking into the crankcase. He did this
by brazing a flat washer with a small hole,
in line, in the tube from the manifold
to the passenger rear of the block. This
restricted the amount of sucking through the tube into the crank case, and if you put the
palm of your hand over the oil fill tube,
sucking there is now very slight. With the choke fully open, the truck now idles
perfectly. Anyone have an idea what caused
the super vacume sucking into th crank case until he restricted it ? Is there a check valve or something that is suposed to be in the pipe at the manifold ? Thanks in advanced. Bob Stopka.
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