Posted by Northern Calif Dave on Tuesday, September 06, 2005 at 7:52PM :
In Reply to: Re: Chris posted by Andy (In MI) on Monday, September 05, 2005 at 9:29PM :
I went through this on my 48 a short while ago, and we added a brake booster. Todd and Clint are probably the best source of knowledge on this subject however.
Since we operate slowly and in dusty conditions with our truck, we removed our road draft tube and replaced it with a tube from the crankcase to the metering valve. Second a tube runs from the air cleaner to the oil filler tube. By doing this, the crankcase air is mixed with the fuel-air mixture and sucked into the combustion chamber, where it is ignited then dumped through the exhaust port and expelled. This sucking action causes clean filtered air from the air cleaner to flow down the oil filler tube and through the crankcase then out the tailpipe eventually. Its basically a closed circuit system that allows only clean filtered air to vent the crankcase at any speed, whereas the road draft tube only operates above 25 mph (although during idle you can see fumes dropping out because they are heavier than air, ect). Of course the road draft tube can get plugged too for no ventilation.
The brake booster is plumbed to a vacume port on the carburator adapter base causing vacume on one side of the brake booster diaphram. The other side of the brake booster diaphram runs to a filter just below the drivers seat. Different system entirely from the Positive Crankcase ventilation system (pcv).