Crankcase ventilation. It is suction from the inlet manifold that lifts the
carb pistons, and it is a portion of that vacuum that acts on the crankcase
to ventilate it. As such the amount of vacuum and flow of air in
ventilating is controlled by the position and size of the ports in the carb
bodies. Disconnecting the pipes, or removing the oil filler cap, allows a
greater flow of air though those ports, weakens the mixture, and will affect
running. If yours won't start with them connected but will with them
plugged then it implies a weak mixture. The fact that the engine still
stalls with them off and the ports plugged indicates that you have a
significant problem elsewhere that is nothing to do with the crankcase
ventilation system, earlier HSs didn't have these ports anyway. It is quite
in order to do your diagnosis with these ports plugged as it does remove one
variable. Sounds like a major vacuum leak, the first place I'd check is to
confirm that the rear Welch plug on the inlet manifold is in place (although
if your 18Hg is measured on the inlet manifold it's doubtful the plug has
come out). After that fuel delivery, piston/needle operation etc. Does
pulling the choke make any difference?
PaulH.
----- Original Message -----
> Would you please clarify the purpose of the hoses that go from the front
> engine side cover/oil separator to the vacuum ports on the HIF carbs? Is
it to
> pull crankcase fumes into the intake for combustion or provide a vacuum
signal to
> lift the pistons in the carbs?
>
> If I have the hoses connected to the carbs, the engine will not start. If
I
> remove the hoses and plug the ports, the car will start (18 in Hg @ 1000
rpm)
> and run for 30 seconds or so before it loads up and stalls.
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