Why you should not vent the L/H valve cover on 1600 motors

[OLD VW NUT]

I read thread after thread about guys having problems with oil control on their motors - especially the 1835 and larger motors. The usual suggestion is to add extra vents on the valve covers. I'm going to show you why that may not be a good idea -thanks to Muffler Mike's efforts in researching his own oil leak problems - and how he found the cure for that leak.

Check out these photos from Muffler Mike's website:

http://www.mufflermike.com/news2000.html

This is a shot of the right side valve cover at 5000 rpms - very little oil pooling up in the valve cover

http://www.mufflermike.com/791.jpg

This is a shot of the left hand side at 2500 rpms -its beginning to fill up with oil - 3000 rpms is cruising speed on the freeway for most bugs/ghias. And you thought your oil was in the sump and doing it's job!

http://www.mufflermike.com/751.jpg

This shot is with rpms 'coming up' to 5000 rpms:

http://www.mufflermike.com/752.jpg

And at 5000 rpms the left hand valve cover is FULL of oil!

http://www.mufflermike.com/753.jpg

A 1600 based motor with no add-on sump holds about 2.6 quarts of oil. How much oil do you think that valve cover holds at 3000 rpms? I'm guessing more than 1/2 a quart. If you have aftermarket valve covers like I do that valve cover holds even more. And if your engine sees 5k rpms on a regular basis and you see the oil light come on - your motor is starving for oil. Don't vent the left side valve cover - instead do like I did with my motor and run a dump hose from the left hand valve cover to the add-on sump. Its a PITA when I need to adjust valves but its worth the effort IMO.

Now you know where your oil is during a cruise on the freeway - and why that left hand valve cover seems to perpetually leak. Any motor that sees 5k or more rpms on a regular basis should have a drain installed to return oil to the sump - and IMO an add-on sump is mandatory with the large high rpm motors. Even a stock 40hp motor will do this.
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[spencerfvee]

I all ways thought that there was a lot of oil in the valve covers at high RPM every time I see a big motor in a pipe buggy or bug with no deep sump . I just shake my head. and the next time I see them. there motor has wiped out the fly wheel main bearing . and they don't understand why . the buggy guys will say theres no room for a deep sump . or no one runs a deep sump so why should I . next time they blow a motor up I am going to show them the pictures mike posted on his forum thanks vw nut for posting spencerfvee

[bugguy1967]

I no longer vent valve covers on my builds. If vents at the case cannot suffice, then there must be a bigger underlying issue. On mild builds, I vent with the fuel pump mounting location and the stock stand. On bigger engines, I add another behind the shroud. Some say it weakens the case, but I haven't had any issues yet.
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"A petrol engine can start readily, run smoothly and give every appearance of being in good order, without necessarily being in good tune." - Colin Campbell, "The Sportscar Engine"

[scotth17]

Let's assume that the 3-4 side head is 3/4 full of oil at some given point. Wouldn't a vent be sort of an air break? I run vents on both sides and the gen tower and have no oil spilling out or such. I think a more interesting test would be the same setup with a clear vent tube in that valve cover routed up to where people normally mount breathers. Maybe test windage pushrod tubes also? Seeing is believing...

[vwracerdave]

I believe the 3/4 valve cover absolutely needs a air vent so oil can return back to the case. Without a vent the oil has to gurgle back into the case. Turn a bottle of soda upside down and watch the air gurgling into the bottle while the soda is gurgling out. Now poke a hole in the top and watch the soda flow out. The vent tube needs to be on the top of the valve cover towards the front of the car. Upon rapid acceleration oil is forced to the rear of the valve cover. Most people add the vents to low on the valve cover and oil can flow out the vent and spit oil into the breather system.
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[Juanito84]

[slalombuggy]

When you vent the 3/4 valve cover all you are doing is giving more oil more room to go to. Once the cover is full it will start being pushed up the breather hose and if you don't have a big enough breather tank you will find out as oil will be everywhere. By not venting the cover eventually it will create enough pressure in the cover to keep more oil from being slung up the tubes, yes it will be slow to drain back, but this is where the return line to the sump comes in. My engine sustains over 5500rpm for more than a minute shifting at 7500rpm and I can check the valvetrain after a run with no more oil dripping on the ground from the 3/4 side than the 1/2 side. I don't vent my 3/4 cover at all. I do vent 1/2, the fuel pump blockoff and run a CB breather tower. A also port the holes in the case going into the pedestal area, above the main bearing webs and a couple of other spots.

brad

[bugguy1967]

I've seen race cars tap into the bottom of the head right before the valve cover and run a steel braided hose to the external sump. Seems like a good idea for any car, but may be overkill on stock.
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"A petrol engine can start readily, run smoothly and give every appearance of being in good order, without necessarily being in good tune." - Colin Campbell, "The Sportscar Engine"

[ralf]

bugguy1967 - then maybe tapping the head for NPT and hose would be cheap enough for stock builds just a thought..


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a coke bottle has 1 hole to drain from.. = pulls itself a bit from pouring out

we got 4 pushrod tubes on the 3/4 side + 2 additional drain backs

even with 1 drain back to the sump thats 5 routes
like slalombuggy says.. this is enough

and vent 1/2 side..

afterall .. these pressure buildup + oil thrown are all coming from the center/case

aleviating pressure at 1/2 side would mean more strength on the 3/4 side to push/return the oil down
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[mark tucker]

I think there was another issue with that motor, like the oil pressure relief valve, the exhaust for that valve is where?? yes right at the #3 exhaust pushrod tube.and it was probably filling the vc from that.might of had a bad spring, stuck open valve, or just way too much oil pump.
the cam&lifters are between the crank&the sump, and the cam is spining the other way, so it should be filling the 1-2 side, but it's not.it's the relief port.

[Dale M.]

Two things I did not see mentioned is also using extended (windage) pushrod tubes and "windage tray" in sump, windage trays seem have fallen out of favor and I do not know why, though I don't use one.....

I vent 3/4 side, use additional 3.5 quart sumps and never have a oil buildup leak or breather overflow problem and my engines see 7000 rpm quite often...

Dale
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All suggestions and advice are purely my own opinion. You are free to ignore them if you wish ...

[jhoefer]

Would things work better if we could vent the valve covers to the top of the case directly and separately so as not to be routed through a breather box? Then run a separate breather line just for the case, like right off the oil fill.

We want the covers vented for drainage but the 3/4 side can overfill and flood a breather box, right? If the vent line went into the top of the case instead, you'd have a vacuum break to let oil drain out of the pushrod tubes, both the pushrod tube openings and the vent opening would be at the same air pressure in the case, so pressure differentials wouldn't really be pushing the oil anywhere more than it already is (not counting windage), and if oil does overfill the valve cover, it gets pushed through the vent line directly back into the case where we want it anyway. And by keeping the actual case vent away from the valve cover vents, we don't risk oil being pushed out the breather because we didn't have a large enough drain line on the breather box to accommodate that excess oil.

Does this seem sensible? Am I missing anything? Are there any good spots to tap into the top of the case without compromising strength or risking breakage? Fuel pump hole is an option of course for those with electric pumps, but I think this idea would work best if each vent line was separate, not T'd together into one spot.

[Eaallred]

I stopped venting valve covers and only vent the case these days.

Once I did that, my breather box and valve cover issues went away completely.

Venting valve covers is a V8 thing. It's the "top" of their motor. There is no practical way to vent the block on a V8. On a VW we have access to the top of the engine case. Seems a good place to add a "crank case breather", right?
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[Juanito84]

The Jaycee system would bypass the oil back to the pump before it goes through the oil cooler, right? Unless you had an external oil cooler and put the Jaycee system after it.

But back on the oil gushing out the pressure control valve and filling up the LH valve cover. Is there a way to direct that oil flow either torwards the crank case pickup tube or even better yet, plumb it to the pickup tube itself? Kind of like the Jaycee system but using the stock valve in the stock gallery.
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If a water cooled engine cools its water with air, isn't it just an overcomplicated air cooled engine?

[modok]

yeah, use one windage pushrod tube on #3 exhaust, this blocks right in front of hole the oil comes out, then port a groove from the hole down so it directs the oil downward.

The WBX oil system plumbs the relief into the pickup line like you describe. That is of some interest and also the grooved relief bore. Some of those did eat rod bearings for no good reason, but I do not know if the cause of that is any fault of the oil system or people putting motor honey in it to keep the light off at idle.

[Juanito84]

[modok]

They don't cost very much, and besides, if you want to convert them to STD pushrod tubes just cut the extended part off.

[Juanito84]

Found one!

http://www.piersideparts.net/MB8530.html
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If a water cooled engine cools its water with air, isn't it just an overcomplicated air cooled engine?

[AlteWagen]

just buy the whole set

http://www.cbperformance.com/ProductDetails.asp?ProductCode=1557

or stainless if you really need it

http://www.cbperformance.com/ProductDetails.asp?ProductCode=1559