Harold,

If you drill and tap the manifold, I would be very concerned abour getting debris in the intake that may cause engine damage. If you do it in place I would suggest removing the air filter assy., stuffing a rag in the intake manifold, drill and tap above the rag. vacuum out any debris and then remove the rag. Removing the intke manifold and completing this off the engine would be safer. Another option would be to simply remove the filter assy., and drill a hole in the base of the filter assy and install a fitting in the base plate. Make sure to safety any hardware on the intake side of the assy with lockwire, Lock Tite or something to prevent loose harware from being injested into the engine.

There really shouldn't be much engine odor, does your crankcase vent run to the air intake? If it does and it's not plugged and the intake filter is clean any crankcase fumes should pretty much go straight into the engine and be burned. If it's a diesel smell then I'd be checking the exhaust system thoroughly for a leak, certainly that's pretty common. If you're getting a lot of crankcase blow by I'd be thinking you might have badly worn rings. We pretty much get no crankcase odors at all.

You might want to talk to a real diesel engine guy before you jump into this. Diesels are unthrottled engines unlike a gas engine. There is little or no manifold vacuum. You are introducing a potential secondary source of combustion air which could be a dangerous thing to do in the event of an engine runaway.

That's exactly what I did.

Drilled and tapped the intake to reintroduce the gasses back into the intake.
Used a rag to block the shavings and then vacuumed them out with the rag still in the intake.

Position the rag past the point of tapping so the shavings fall into the intake on the oppostite side of the cylinders so the shavings can be sucked out without disturbing the rag.

I think the drawback to reintroducing the gasses into the filter assemble is the potential for dripping oil in the engine compartment.

One owner, who wrote a tutorial under the project section,
added a oil separator to reduce caking and sludge to the top end.

Harold,
If you are willing to take off the intake manifold, it is very easy to drill and tap. It's cast aluminum. Before I did it, I spoke with several W/U reps and they all said it was a good idea. I personally would not want to drill and tap it in place. With a fitting on the manifold, you never have to worry about cleaning an air filter, and the "oily mist" smell completely goes away. I hightly recommend it.

My vent tube came from the factory cabled to the air cleaner housing, so that the end of the vent tube ends right at the intake 'horn'. Whatever crankcase gases might come out of the vent tube are immediately sucked right into the air cleaner.

I'm not sure I'd want to plumb that hose directly into the air filter. If for some reason any significant quantity of oil were to be blown out of the vent line and into the intake, the engine could ingest that oil and you might not be able to stop it. Diesel engines just need fuel (like oil) and compression to run, so if you can't cut off the fuel..... I'd not like find out that I overfilled the crankcase on my last oil change by having the engine destroy itself.:eek: A small risk perhaps, but that's why I wouldn't tap it directly into the air filter or worst, manifold.

My 2 cents (perhaps worth even less :D