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I've been thinking about venting my crankcase. What I was thinking about doing was to drill, tap, and thread my fuel pump block off plate, install a fitting, and run a hose. What I haven't decided yet is whether to install a catch can, or just run it up and tee into the large valve cover vent hose. I'm just afraid it might actually suck up some liquid.

What ya think?

Jc
 

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The large hole in the valve cover is for fresh air to enter via the air cleaner, so I'm guessing you won't be venting the crankcase that much through that hole, you may be putting oil mist in the carb, depending on the crankcase pressure.

Ron
 

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vent?

Not to argue with Ron, but the air flow in that top vent already goes both ways. The metered orifice attached to the small hole in the valve cover draws a slight vacuum on the entire crankcase. This vacuum is relieved through the "big" hose with filtered air from the inside of the air filter. When crankcase pressure, usually from blowby, builds to put an actual pressure in the crankcase, the big hose allows this excess to vent into the air filter and into the motor to be burned. A lot of guys with higher mileage motors notice the oil in the carb asa result of this.

With good fittings on both ends, good hose in between, and clean screen inside the valve cover this should be enough vent to keep the pressure from building. If you do want another vent, for whatever reason, I think the side cam cover in the head would be a better choice than the fuel pump block-off plate. It is much higher in the motor, and being steel might be easier to weld a stand-pipe or something to.
 

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Re: vent?

oldopelguy said:
If you do want another vent, for whatever reason, I think the side cam cover in the head would be a better choice than the fuel pump block-off plate. It is much higher in the motor, and being steel might be easier to weld a stand-pipe or something to.
I like this idea Stephen. I think that having a breather tube angled upward would be important (spinning cam throws a lot of oil), but the fact that it's a removeable plate makes it appealing. It might work very well on a racing engine too, tying in the valve cover, the cam cover, and maybe a crankcase vent as well to equalize the pressure in the different areas of the engine. We used to launch dipsticks in our old racing engines, and that was with less than 3% leakdown, so you can see how high crankcase pressures can get. Hmmm, another project for me to consider...

Bob
 
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old motor tales.

Back in college, when I ran around in an Opel with a LOT of NOS, I had a lot of issues with crankcase pressure. What I ended-up with was a piece of 3/4" conduit about 6" long with a slight bend on the bottom so that it came straight up but angled into the cam cover. On the bottom of the tube I added a 3/8" nipple going straight down. A hose was then run from this barb to one screwed into the extra dip-stick hole in the oil pan. I just had a little K&N filter on the top, but it would be very easy to route it almost anywhere if desired. Usually the extra oil drained to the pan, but if pan pressure got excessive it would relieve up the tubing and any entrained oil would fall into the side of the head instead of going up to the filter. That stand-pipe did a lot to keep the oil and pressure issues to a minimum, enough in fact that any time I build an Opel motor for real performance I'll definatly be incorporating the feature.
 

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Old Opel Guy is correct in that the air flow is in both directions on the large hose, I forgot about there not being a PVC valve in the plumbing like other cars. That's what happens when you get on the net at dark thirty, when I should have been horizontal between the sheets.

Ron
 

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Crankcase vacuum

I was just reading an Internet Tech Tip in an old Blitz (6/2000) about crankcase vacuum. In it there is a description of a hose teeing into the brake booster hose and leading to the valve cover, with an adjustable valve plumbed in. When the small line from the valve cover is plugged this creates a vacuum in the crankcase. The valve is adjusted until a vacuum at the oil filler hole is detected. This vacuum helps to reduce oil consumption.

Is this something we should consider doing on our cars. I have noticed on my 77 Datsun Z that there is a vacuum at the oil filler hole. It has a bazillion miles on the engine and doesn't leak any.... but does burn a little.

Any additional info appreciated.
 

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Hey, let's open this can of worms again! We were almost getting somewhere in a closely related thread recently but it died off.
With my top end oil control issues I am presently using a pcv valve to create a vacuum, and at idle (mine idles about 1200 rpm) it is pulling a good crankcase vacuum. Haven't measured it yet. I wonder what it's doing at 7000 rpm. Then there's Bob's input that this method causes lower fuel octane. And what about using the header collector to cause vacuum like in drag race cars? Any input out there from our resident geniuses? Thanks!
 

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I've been thinking about this issue too. Because of the compression I run I can't put it into the engine. I can tell that there is some oil vapor from the big vent hole especially at higher RPM so I need to do something. I'm currently modifying a cover that I intend to block the small hole and either tap the large one and install a 90 degree fitting or mount a flat plate type breather there.
 

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dave if you are talkng about where to or what to do with the oil vapours then why not build a collector bottle and plum the vent to that
all residue can be put into a can and tacken to your local recycling plant/point
the bottle can have a filter so as not to upset the greens (after all you recycle the waste)
if you dont give a damm for the greens run the breather to the chassis rail and stop rust!!
 

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Just an idea on where to put the oil from the vapor. Come straight out of the large port to a Tee fitting. top of the Tee would be a breather and out the bottom would be a line bulkheaded back to the valve cover or some other return area. Maybe the block or upper pan to equalize pressures.
 

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I guess the question would be, how much liquid can you remove from the crankcase vapor? It seems the way to find this out would be to take a tube about 2" in diameter, maybe about 18" long, loosely stuffed with a coarse steel wool. Then cap both ends. Each end needs a 3/8" barb fitting to hook a hose to. Mount the tube vertically in the engine compartment. Run a hose from the bottom of the tube to the valve cover vent, and a hose from the top of the tube to manifold vacuum. Then go enjoy your Opel for a while, stopping a couple times to check your oil level. If you have to add oil, the missing oil may be in the tube, gravity should make it be at the bottom. Pull the bottom hose off and see how much oil comes out.
If this seems to work, and isn't collecting so much oil that it fills up the tube and puts oil into the intake manifold, maybe a tiny drain could be put in the bottom of the tube so it drains back to the pan when the lack of vacuum allows it to.
Anybody wanna give this a try? Speedway GT is put away till spring, maybe we can do it then.
Offhand I can't think of any other way to do it. Anybody else got an idea?
 

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Hey, another thing to consider here: just how does oil get into the air inside your engine in the first place? In all out high tech racing, part of the plan for oil control is to keep oil in the pan so it is available to be picked up by the pump. And you want it to be just oil, not a frothy oil/air comb. That's the reason they have dry sump systems, but let's not go there.
Anyway, the oil coming out of the main and rod bearings is being whipped around by the crank and rods. We've discussed the crank scraper, it strips a bunch of this "windage" off the crank and rod caps and drips the oil pack to the pan. So there went some of it. Next, in the case of the Opel idea of draining the head down the block and dumping it onto the crank, I don't like that one bit and you may recall how I changed that on mine. Then, upstairs, the timing chain must throw a bunch of oil up, especially as it goes around the corner (cam gear). So on my valve cover spacer, (which is really a baffle to keep some head oil from climbing the right side of the valve cover) I made it run real close to the timing chain to help strip some oil there. Better yet might be a little hood over the timing chain/cam gear to keep the oil from wanting to be pulled into the vent.
That's it. The valve cover is coming back off soon. We got work to do! Still got to perfect the valve timing anyway, I know it isn't quite right...
 

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And Dan gets the prize for resurrecting the oldest thread of the year so far :)
 

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Timing cover venting

Ok, it sounds like a good place to vent would be at the fuel pump cover plate, that way you can remove, drill and install 3/8 barbed fitting, then run to a catch can. If you're just trying to relieve the pressure then couldn't you vent the can w/ filter? Why would you need vacuum from the intake manifold? You have that on the big hose from the valve cover already. Then I would add a drain plug of some type, small ball cock valve w/drain line, either to the pan or a can. No Baz I'm not draining it to the frame rail, it already has enough on it :haha::haha:
 

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Oil Catch Can

Hey folks-

I ported the the outlet hole by .25 inches when I initially started working the engine over. I then routed the outlet hoses to a vented oil catch can which is mounted just forward of the right side engine mount. The return venting hose is the same diameter and mated on the forward portion of my cold air intake, just aft of the filter.

I have found that my oil pressure has finally stabilized through all RPMs and (!) there has been zero oil return through the intake.

just thought this might help in the whole decision bit. Have a great one!

-Gabe
 

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Hey folks-

I ported the the outlet hole by .25 inches when I initially started working the engine over. I then routed the outlet hoses to a vented oil catch can which is mounted just forward of the right side engine mount. The return venting hose is the same diameter and mated on the forward portion of my cold air intake, just aft of the filter.

I have found that my oil pressure has finally stabilized through all RPMs and (!) there has been zero oil return through the intake.

just thought this might help in the whole decision bit. Have a great one!

-Gabe
Funny you should mention this. I noticed that my oil pressure varied throughout the RPM range, and got noticeably higher when downshifting. I wondered if crankcase pressure might be causing this. Eventually I found that the hole in the intake manifold (the one that the small tube from the valve cover connects to) was undersized due to epoxy around the fitting. Since I drilled that out the oil pressure remains constant throughout the RPM range.
 
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