My Cummins main engines are 1996 vintage and came with a very basic arrangement for dealing with crankcase fumes: a metal tube connects a hole in the crankcase to a housing that contains a coarse steel wool-like metal filter that’s supposed to condense oil on it and let it drip back into the crankcase. A hose was routed from that housing down to the base of the marine gear. That’s it. It just vented fumes, oil mist that didn’t condense, etc into the bilge.
I previously owned a 1967 Chris Craft Constellation 52 that had Detroit Diesels, so I know how nasty bilge spaces can get when venting crankcase fumes straight into the engine room. I was somewhat familiar with Walker Airseps, but at $750/engine I just tolerated the mess in my Connie. Racor also makes a Closed Crankcase Ventilation system that retails for ~$550; again, too rich for my old Connie.
But with my Roamer, I’d like to control the engine fumes. Tony Athens over at Seaboard Marine has a great article that discusses the various CCV systems and provides a bullet list of features that he believes good CCV systems should have. One of the things he’s particularly critical of is CCVs that dump the liquid in the fumes back into the oil pan. He ends by discussing his EnviroVent CCV system for the Cummins B-series engines. Mine are older generation C-series, but as I looked at the pictures of the EnviroVent installed on a B in the article it was obvious I could make something like it for my engines.
It was only after I started buying components that I realized Tony also makes an EnviroVent for 6CTA engines like mine. The price: $375 each. I thought I could beat that.
I found the best prices for Greenleaf nylon fittings at Tractor Supply
$31.91 for all the fittings for both engines
That’s a 1″ hose barb, a 1″ Tee, a 1″MPT to 3/4″ hose barb, a 1″MPT to 3/8″ hose barb, and a 90° 3/4″ hose barb.
Probably unnecessary, but I assembled the fittings with GasOila
The engines came with new air filters, so there’s no additional cost for them
I used a hole saw to make space for the 90° hose barb
The hole was just the right size to thread in the fitting.
The fitting snugs up tight to the air filter end cap
1″ Shields Rubber Series 141 Multiflex Hose was $18.49 at West Marine
In the picture above, you can see the OEM crankcase vent filter in the upper left corner. From there, a 1″ hose used to be routed down to the bilge near the ZF gear. In the lower right corner of the picture, you can see that I routed it inboard of the engine stringers to the Tee.
From the Tee, the 3/4″ hose goes up to the fitting on the air cleaner
I had leftover 3/4″ Multiflex hose that I use for bilge pumps, so there was no additional cost, but it would have been ~$16 at West Marine. And this appears to be the same hose Tony Athens uses for his EnviroVents.
Aluminum coolant overflow reservoirs were $23.47 for two on ebay
Bicycle water bottle cages were $10.44 for two on ebay
I think these bottles look better and are more robust than the clear plastic condiment squeeze bottles used in the Seaboard Marine EnviroVents.
The water bottle cage holds the reservoir firmly, but it pops out easily when it’s time to drain the contents.
I installed the cage at an angle because the reservoir is unvented
As Tony described it in the article, fumes condense as liquid on the long hose going down to the Tee, so mostly only gases and air take a turn up at the Tee and continue on to the air filter. Vacuum from the turbo inlet is present inside the air filter and will also be present inside the hoses, which will provide positive (rather than passive) crankcase ventilation.
The liquid will run down the hose and accumulate at the bottom of the Tee until it spills over into the 3/8″ hose and drips into the tank. Since the hose enters the tank near the base it’s necessary to orient the tank at an angle to maximize the amount of liquid it can hold. Once the liquid level gets up to the hose, it’ll back up into the hose since the tank is unvented. If I vented the cap of the tank by drilling a hole, engine intake vacuum would draw unfiltered air through it. I don’t want that, so I think my approach is the best compromise.
Oh, and the mount for the cage is just a piece of 1″ wide 1/4″ aluminum bar cut from some scrap. I coated it with Bar Rust 235 epoxy barrier coat after drilling and tapping the mounting holes.
Starboard side is done!
Similar approach on the port side
Total cost for my DIY positive crankcase ventilation systems on both sides: $100.31.
Next up in our 1969 Chris Craft Roamer 46 Refit: Helm Windshield Wrap Up
1969chriscraftroamer46 
My experience with the 8.3 is limited, compared to the 5.9, so don’t take what I say as gospel, because it may not be applicable to the 6CTA. I do know that the C engine has a much better crankcase vent system than the B engine. The system needs to be vented, otherwise you’ll blow out the tappet cover. Also, you want a fairly straight run with the hose to the catch can so oil does not pool in the hose, but it seems like that’s going to be inevitable with the way your catch can is configured. Finally, put some kind of filter in the can itself, most guys use steel wool.
Thx for the suggestions. The 1″ hose from the OE crankcase vent filter heads downhill from start to stop at ~45°. It will be impossible for oil to pool anywhere except in the Tee before it spills over and drops into the tank via the 3/8″hose. No air passes through the can, so there’s nothing to filter. It’s purely a reservoir for liquid that drips into it.
If I understand your system you are returning crankcase oily vapor to the intake side of the turbocharger. Regardless of oil condensate filters and traps SOME oil will enter the turbocharger and the blades will, over time, become oil coated. A periodic inspection and cleaning schedule could be established to clean the blades if you find the oil in the turbocharger to be undesirable. Perhaps every 100 operating hours or an interval to match your oil changes would be useful.
Hi Butch! The design of my system is identical to Seaboard Marine’s, and Tony over there says (in the linked article) the long run of 1″ hose from the OE vent outlet to the Tee does a good job of condensing the oil mist. Still, periodically checking the turbo is something I plan to do annually anyway. Thx. Q
With a sealed catch can most oily fumes will bypass the can and flow to your air cleaner. You might want to add a vent line to the top of the cans to the air cleaner also, so the oil has an easy path to the can.
Hi Dan!
You might want to take a gander at the article about CCV systems I linked to by Tony Athens over at Seaboard Marine. That article focuses on the B-series Cummins engines, which are apparently pretty bad at venting lots of oil. The C-series engines I’ve got don’t have that problem; most oil fumes are caught in the OE vent filter and returned to the crankcase. But my design is fundamentally identical to Seaboard Marine’s EnviroVent. As Tony explains, the inner wall of the 1″ hose from the OE crankcase vent filter is much cooler than the inside of the crankcase and the gases leaving it, so oil and other vapors naturally condense quickly on that inner hose surface. The hose heads downhill from start to finish at ~45°, so condensate will naturally drip downward until it hits the Tee, before it spills over and drops into the tank via the 3/8″ hose. The 3/4″ hose going from the Tee up to the air cleaner is even further away from the crankcase outlet, so it’s cooler still, so any remaining vapor will naturally condense there. Tony also makes the point that longer hoses collect more condensate. Since my hoses are ~1′ longer than the ones he uses on his EnviroVents, mine should be even more effective at condensing any oil fumes that make it past the OE filter.
If, after running it for a while, I find it’s not doing the job well, I’ll reassess. But comments from B-series Cummins owners suggest the EnviroVent system is very effective at catching oil fumes. They don’t come with a vent line from the puke can to the air cleaner.
Cheers,
Q