Posted by RDavis on Saturday, July 26, 2003 at 1:17PM :
In Reply to: more info Re: 61 WM300 VACUME BUILD UP IN CRANKCASE posted by Bob Stopka on Saturday, July 26, 2003 at 9:07AM :
The 251 in my 64 WM300 has a factory riser that sits on the carb. The oil bath filter sits on top of that. The riser has a nipple like the oil fill tube and these two are connected by a rubber hose. The crankcase fumes are not sucked and vented through the oil bath filter. If you take off the oil bath filter, the suction or vaccum exerted on the crankcase is reduced. When the oil bath filter is replaced the airflow is restricted casing more suction on the crankcase or from the path of least resistance. I assume either you are using too thick a weight of oil or the oil in it has become dirty and thicker restricting the airflow causing more vaccum on the crankcase through the vent hose which is somehow preventing the carb from properly metering the correct amount of fuel to idle?
Of course I'm just going on what I've read in your post, there might be other factors I am not aware of. Have you checked the vaccum connection for the dist. advance ?