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 