Crankcase venting alternatives - thoughts

[tony-muscle]

I am running an open crankcase venting system with valve cover breathers. I am not trying to reinvent the wheel but trying to understand. So the gasses blow-by through the piston rings to the crankcase, from there they escape up the head oil return holes up to the valve covers. Some gasses may make it through the valley pan and thought the head lifter bores to the valve cover. As the gasses travel up the oil drain holes they are going in the opposite direction, which in some way has to slow down the oil drain back from the heads. I can only assume this gets worse when a high RPMs. Since the Clevelands are well known to have poor drain back I am wondering if venting the crankcase gases through another route can improve the drain back from the head to the oil pan. I first thought an idea borrowed from other applications to help vent through the oil dipstick tube. However, I think this is too small to make much of a difference. Then, it occurred to me that my oil pan has a second port on top of the sump tank (https://kevkoracing.com/collections...07-ford-cleveland-front-sump-t-style-drag-pan).

It would be very easy to hook up a hose to this port, add a breather on the other end and run it up to the area where the distributor is. I could add some of that stainless steel scrubbing scotch-brite inside the hose to try separating any oil from the gasses. In any case, I think this will be very cheap to test. The benefit is that it will help vent the crankcase without having the gases travel up the oil drain holes. I will use it in combination with the valve cover breathers to assure plenty of venting available. Opening this thought here for criticism.

BTW, the oil level in the pan sits about 5/8" below the top of the sump tank when filled up to the factory dipstick. I have the dipstick marked where it will be flushed with the top of the tank. I typically fill up oil close to this mark for AutoX or track use.

 

[Duncan Mach72]

That sounds like quite a good idea. David Vizard discusses oil drainback & crankcase pressure a bit in his big block Chevy book & he states that if you run oil drainback lines from the heads to the pan they need to be about 3/4" bore because of the air/fumes would go upwards in them. Obviously your fitting will be submerged when you brake & maybe hard cornering but hopefully not a problem.

 

[mjlan]

I wouldn't worry about this until its a real problem not a theoretical one.

Is the oil drain-back issue real or is it an internet problem?

 

[Hemikiller]

You're forgetting about the hole knocked into the casting right behind the front China wall that leads to the timing chain. You're getting plenty of venting through that, which is about 1", and the four drainbacks in the lifter valley. The 16 pushrod holes in the head provide plenty of volume on a 4V head, and even more on a 2V as there are large openings around the ports.

The port in the pan is probably 1/4" NPT, not enough volume to vent much of anything. Vacuum pump systems on race engines typically use a 12AN or -16AN inlet in the side of the pan, or in the front of the valve covers.

If I wanted to try venting the crankcase directly, I'd look at the fuel pump boss, or the timing cover.

 

[droptop73]

In pre PCV days engines used a road draft tube that created a slight low pressure as the car moved down the road to vent the crankcase. After PCV valves were introduced the low pressure came from the intake manifold so the gasses could be burned in the engine. If you are just running breathers there is nothing creating a low pressure to draw fumes from the engine. The only method to move the gasses is raised crankcase pressure from "blowby". I'm not sure this is the best for power or efficiency. Many higher powered race engines use a pump to introduce a vacuum in the crankcase to improve ring seal and reduce windage increasing power. While you want to make sure the crankcase is well vented you'll need some way to move the air. A PCV is a simple way to do that.

 

[mjlan]

Tony- when you say you have an open crankcase with breathers do you mean you aren't pulling any vacuum on the crankcase?

If you aren't I'm curious why.

As others have suggested, engine longevity and performance are all based on there being negative pressure in the crankcase.

Edit: the above sentence isn't exactly correct, what I meant is that the engine should see vacuum in the crankcase at times (either from a PCV, road draft tube, header evac system, vacuum pump etc.) in order to keep crankcase pressure down to a manageable level....

 

[will e]

High RPM's happens while accelerating which means low vacuum. So the oil drain back at high RPM's is going against little to no crank case venting.

 

[c9zx]

How about using PCV valve to a true oil separator (not a catch can) to manifolds vacuum. You would have the benefits of a PCV system while greatly reducing the amount of oil into the combustion tract. It woks very well on my 2007 Mustang GT. Chuck

 

[Don C]

I would be hesitant to use that location for a crankcase vent. While the foam or chore girl helps separate the oil from the crankcase fumes in the breather cap on the valve covers (where it is dealing with only mist or droplets) I don't think it will be effective in a tube, in fact, may work just the opposite. Consider this scenario, you hit the brakes out on the track, oil fills the front of the pan and pushes into the tube, the chore girl keeps the oil from quickly draining back into the pan, you're pulling high vacuum decelerating, pulling oil further up the tube, you come out of the corner, mash the gas pedal, to the floor, pressurizing the crankcase.
It would be a good location to drain the oil to from the oil separator that Chuck mentioned. I like Hemi's idea of using the timing cover. The valley used to be a good place to connect road draft tubes to on "Y" blocks. There's a couple of places on the rear of my intake manifold where a vent tube could be tapped into from the valley.

 

[tony-muscle]

Thank you, there are all very good ideas in here.
I am willing to give this a try in a few variants because I only have to spend $20 in fittings. I have the hose and the breather. If it doesn't work then I have not done anything permanent.

@Don C , I will try first with none and then with the scotch-brite high up near the breather to see how much oil I get. Actually, our manifolds have a great location to pull vacuum from the valley which is via the exhaust crossover if properly blocked at the heads. I thought one could drill a hole on the valley side of the crossover and add a fitting on the exterior, or if you have an EGR fixture like the Blue Thunder then you already have the hole. However, this will be more destructive as a test than the oil pan idea.

@c9zx , the problem I was having was that the vacuum was sucking the oil from the valve cover. It could be my valve covers, but this is with baffles and scoth-brite in the chamber between the baffles.

@mjlan , right now I am trying open breathers without PCV, or open per the reasons above.

@droptop73 , @c9zx
In regards to vacuum and PCV, yes it is correct that vacuum will place less stress on the seals and perhaps gain some HP. However, the great fault of the PCV system is that there is no vacuum when you most need it, which is during hard acceleration. When flooring the pedal, vacuum goes to zero and that's when you are loading the engine the most. Therefore, an open system with 2+ breathers will do a better job of evacuating the gasses and keeping the crankcase pressure as low as possible - more open vent areas means less pressure. With the PCV and no vacuum in hard acceleration, the gasses evacuate via the inlet breather and through the small PCV valve into the carb but no vacuum. This is less efficient, and during this moment it will create more crankcase pressure than just breathers. Race engines use the vacuum pumps on all the time so they can effectively create vacuum under all conditions to gain a few HP at very high RPMs.

 

[71ProjectJunk]

I would think that there would be issues with trying to vent the engine gases that low in the oil pan, as you are literally into the oil. Hemikiller's suggestion of doing it at the fuel pump or timing chain cover is probably a better idea. I would think that you need somewhere further away from the oil to be effective, so that you are not sucking oil up your vent all the time. The fuel pump boss is probably ideal, as long as you are running an electric fuel pump. You would still need to fabricate some shielding there, as the chain will be splashing oil all over that area, to again prevent the oil from clogging it up and being pushed up it.

 

[tony-muscle]

I would think that there would be issues with trying to vent the engine gases that low in the oil pan, as you are literally into the oil. Hemikiller's suggestion of doing it at the fuel pump or timing chain cover is probably a better idea. I would think that you need somewhere further away from the oil to be effective, so that you are not sucking oil up your vent all the time. The fuel pump boss is probably ideal, as long as you are running an electric fuel pump. You would still need to fabricate some shielding there, as the chain will be splashing oil all over that area, to again prevent the oil from clogging it up and being pushed up it.

Definitely a concern. The good part is that when the engine is loaded the most, the oil will go away from that port. As I said, it is very cheap for me to try. I agree that there are other promising locations but those will be more involved. I really like the idea of using the intake manifold crossover after it has been welded shut. It connects the bottom of the manifold with the top so you just need to drill a hole or holes along the bottom of the crossover and then add a fitting to the top.

 

[tony-muscle]

I added the crankcase vent off the oil pan as explained. I have been running for two weeks with no problems and no dipstick blow out. In these two weeks I run one AutoX event and a few of high revving spirited drives. Actually, last night I replaced the smaller breather I had with the pictured K&N and it was surprisingly very dry of oil. Now I have open breathers on each valve plus the "center" one coming off the oil pan. Keep in mind that for AutoX I run about 1/4" higher oil level than factory. I stuffed a little bit of scotchbrite on the breather hose at about 6" from the oil pan.

Additional breather in "center" - I just wish I could find a breather with blue element like the air filter. However, it is not as noticeable without the flash:


Breather and hose snaked behind alternator bracket:


Attachment point of breather hose to oil pan:

 

[EBSTANG]

Or you could try the Wagner dual circuit adjustable PCV valve. You can adjust the amount of flow &&&&& when it happens because it has a dual circuit. This dual circuit is the basis for the invention. It certainly is interesting. Take some time and watch the videos & read the pretty impressive testimonials. Let me know what you guys think.

http://mewagner.com/?p=444

 

[tony-muscle]

Or you could try the Wagner dual circuit adjustable PCV valve. You can adjust the amount of flow &&&&& when it happens because it has a dual circuit. This dual circuit is the basis for the invention. It certainly is interesting. Take some time and watch the videos & read the pretty impressive testimonials. Let me know what you guys think.

http://mewagner.com/?p=444

I had it for two years and still sucked oil because of the vacuum. Also, with any PCV you will have the oil suspended in the vapor that eventually gets down the intake caking on the valves and pistons. Being a non-daily driver I prefer to keep that junk off the engine.