Big Cam Cummins Stupid Question

Sounds like the blow-by tube. It’s open to the atmosphere.
@BoxCarKidd @SmallPackage

 

Blowby tube…or something left from somebody engineering a while back
Probably about 5/8 diameter?
Get us some pictures so we can help you please

 

Diesel engines don't make vacuum due to no throttle valve on the intake.

What you're describing sounds like the crankcase vent hose (aka blowby hose). Its supposed to be open to atmosphere, it might have a bit of haze and small amounts of oil come out of it, that's considered normal.

 

Let it dangle as low as or a little lower than the front axle. The oil slobber will not coat the under carriage of the truck that way. With them old turbo motors there will always be a drip drip drip when parked and shut down. Can be replaced with a longer piece of 5/8 heater hose if need be.

 

A 4070B, by gar, that takes me back. , one of my favorite cabovers, as if. We called those blow by tubes, "rust proofers". I thought a blow by hose was on a small cam. I don't recall my BCs having them but I guess they do.

 

If you use a big red hose that’s long enough to drag the ground when parked you might get named the donkey dick express…

 

Back 50+ years ago, ALL engines had a crankcase breathers; then the PCV was invented and quickly became required on all cars. It took a while for commercial trucks to require them (like today, where even the largest road-going diesel engine has one), but an old Big Cam Cummins is certainly old enough to have one.