Breathers...calling Sarge, John Lazenby...

[Fritter]

How did the old school guys from DKP 1 not have their high compression engines puke oil all over the place by just using a piece of breather hose vented from the oil filler through the pulley tin? 
 
Or, maybe they did puke oil all over?   

I would love to have some insight here...

[Sarge]

How did the old school guys from DKP 1 not have their high compression engines puke oil all over the place by just using a piece of breather hose vented from the oil filler through the pulley tin? 
 
Or, maybe they did puke oil all over?   

I would love to have some insight here...

If your running any kind of an additional oil sump, I'd recommend lowering the oil level on the
dip-stick to a little above the first line when you check the oil first thing in the morning.  It's also
important to vent the valve covers whether to a puke box or simply a hose from one cover to the
other (over the top of the trans) that has a small notch removed at the top of it's highest point.

[johnl]

How did the old school guys from DKP 1 not have their high compression engines puke oil all over the place by just using a piece of breather hose vented from the oil filler through the pulley tin? 
 
Or, maybe they did puke oil all over?   

I would love to have some insight here...

If your running any kind of an additional oil sump, I'd recommend lowering the oil level on the
dip-stick to a little above the first line when you check the oil first thing in the morning.  It's also
important to vent the valve covers whether to a puke box or simply a hose from one cover to the
other (over the top of the trans) that has a small notch removed at the top of it's highest point.

Sarge has spoken the truth so there is not much I can add.  Oh, back then I don't think it was considered high compression until you hit about the 12:1 ratio........     

[Fritter]

Thanks guys.  In the engine pics I have of DKP 1, there seemed to always be a piece of hose from the stock breather going down to the tin....did you just drill a hole and stick it through the tin?

Did you run the valve cover to valve cover hose in the old days?

[johnl]

Thanks guys.  In the engine pics I have of DKP 1, there seemed to always be a piece of hose from the stock breather going down to the tin....did you just drill a hole and stick it through the tin?

Did you run the valve cover to valve cover hose in the old days?

In my case I ran a hose from the oil filler breather down through an existing hole in the tin.  Nothing fancy but it worked.

Regarding the valve covers I used stock VW and cut a hole at the front upper end with the nipple going up at about a 45o angle.  There was a hose that ran between them with a small opening where it reached the high point over the trans.

[Sarge]

Did you run the valve cover to valve cover hose in the old days?

I still do to this day... no leaks or problems.  Sometimes less is more.
As for the breather hose, I tucked mine between the engine compartment
seal and the rear engine tin.  Everything was soooo much easier back then!

[Fritter]

Simple with as little doodads as possible is best!  

Maybe running the breather hose out the bottom of the car (through rear tin) created a vaccuum as you drove and helped suck pressure out of the case?

I also thought about just running the vent tube to terminate just above one of my 48 chokes, that would get a vaccuum going too!

I have a typical VW breather box mounted on the back of my 40hp shroud (with AL porsche oil cooler inside!), and I kind of want to eliminate the box and go simpler.

I also notice FAT Performance runs a hose to a little gauze breather that they then zip tie to one of the rear engine lid supports. 

Thanks for the advice.

[hotrodsurplus]

I wasn't part of the early crew so I can't speak to that but I have general experience with the matter. An engine with properly seating rings, tight valve guides, and a properly oriented generator-stand baffle should not require any external breathers. Poor engine building and advertising dollars made external breathers popular.

An engine that produces a lot of blow-by pressure likely has poorly seated, worn, or broken rings, warped barrels (running too hot or without thermostats), damaged pistons, or hammered valve guides. Build the engine right, seat the rings properly, and use a thermostat and you can just vent the breather to atmosphere (use a filter of some sort to keep out trash).

[Fritter]

I'm having problems now with my 2332....when I really get on it, oil is spewing from various places, the worst being the front crank seal (flywheel end).

I have both valve covers vented and connected to a cheapie typical VW breather box on the top back of my fan shroud, and I also have a line from the box going to my breather stand.  

I'm going to guess some type of pressure is building up in the box, and making things worse...

I am going to try putting normal VW valve covers on, and venting the oil filler to atmosphere.

Also, my 2332 has under 1k miles, so the rings may not be seated fully, who knows.  

I bet FAT Performance does that one little gauze vent off the oil filler for a reason......they have the experience to know what works.

[Jim Ratto]

Mike are you running a VW case or an aftermarket aluminum one?

[hotrodsurplus]

when I really get on it, oil is spewing from various places, the worst being the front crank seal (flywheel end).

a flywheel seal doesn't leak by residual crankcase pressure. That's actual pressurized oil pushing through the seal. It's possible that the seal was not seated properly, the seal got damaged, or the seal boss was damaged (usually scratched) at one point.

Does it leak at the crank-pulley end? The factory used what's referred to as a labyrinth seal there. There's no mechanical barrier there there so basically gravity keeps oil from exiting at that point. But excessive residual crankcase pressure can overcome that barrier. So oil leaking there indicates excessive crankcase pressure.

I have both valve covers vented and connected to a cheapie typical VW breather box on the top back of my fan shroud, and I also have a line from the box going to my breather stand.  

I'm going to guess some type of pressure is building up in the box, and making things worse...

Does that cheapie box vent to the atmosphere? If the entire system is sealed then the crankcase can accumulate enough pressure to force oil out of seals. That's really common in the racing world with power steering. If you don't vent a reservoir it will build pressure and blow out the pump or rack seals.

I bet FAT Performance does that one little gauze vent off the oil filler for a reason......they have the experience to know what works.

Astute observation.  

[Fritter]

It's a VW mag case.

I think there are two oil drainbacks on the case next to the flywheel seal that could potentially puke oil out, given a lot of pressure in the case.  1 and 3 are pushing a lot of air on a 2332 back there....

At first, it did blow out the pulley end, but that stopped.  Maybe partially because the oil filler breather is directly above the pulley end....by 2 and 4.

Yep I believe it has a vented lid.  But the box is very small....so if all three vent hoses (1 oil tower, 2 valve cover) are venting to one little 'ol box, it may be getting overloaded. 

[Fritter]

It's a VW mag case.

I think there are two oil drainbacks on the case next to the flywheel seal that could potentially puke oil out, given a lot of pressure in the case.  1 and 3 are pushing a lot of air on a 2332 back there....

At first, it did blow out the pulley end, but that stopped.  Maybe partially because the oil filler breather is directly above the pulley end....by 2 and 4.  And, now that I think of it, my breather hose was kinked to the breather box, until I put a right angle fitting on the breather box on the back(tight fit when the breather is behind the fan shroud, hidden!)

Yep I believe it has a vented lid.  But the box is very small....so if all three vent hoses (1 oil tower, 2 valve cover) are venting to one little 'ol box, it may be getting overloaded.  

Like I said, I'll try two non vented valvecovers and an "open" oil filler hose, ala FAT performance.....I'm thinking this may create lower pressure area in the case, so the oil from valvecovers will drain quicker.  

[Jim Ratto]

  1 and 3 are pushing a lot of air on a 2332 back there....

yep, the VW is a real "boxer motor" where opposing pistons are both approaching BDC or TDC simultaneously. On any of the big cc motors I build that are going to see some thrashing I try to open up the passageways inside the case (webbing) or the "hallways" that lead from front to rear (and vice versa) of case. I try to round and boattail the webs that are facing the backside of the pistons to ease the pathway of air getting pumped around in case. It's really on old Porsche trick. A few motors i have redone for guys had puking problems, and opening these passageways up some did stop it. My friend Ray Schubert started doing this about 12 years ago on any of the motors he was building with aftermarket aluminum cases for same reason. He also found oil temperature dropped by about 30F after opening webs up.

[Fritter]

Seems to make sense, Jim.  I will report my findings back here so as to educate everyone else having these issues.

I used to have a 68 911, and the breather system on that thing was huge!  Big old vent connection right in the top of the case that hooked to a big old rubber hose connected to the dry sump oil tank, and then I believe another big old rubber hose went from oil tank to the giant air cleaner used on 911's.  And I remember there definitely was oil in the air cleaner when I took it out and looked at it.  There also is a little brass filter on the air filter connection that has brass wool or something in it...probably a spark arrestor to prevent any backfire from getting to the oil tank.  

[Taylor]

I wasn't part of the early crew so I can't speak to that but I have general experience with the matter. An engine with properly seating rings, tight valve guides, and a properly oriented generator-stand baffle should not require any external breathers. Poor engine building and advertising dollars made external breathers popular.

An engine that produces a lot of blow-by pressure likely has poorly seated, worn, or broken rings, warped barrels (running too hot or without thermostats), damaged pistons, or hammered valve guides. Build the engine right, seat the rings properly, and use a thermostat and you can just vent the breather to atmosphere (use a filter of some sort to keep out trash).

That's not entirely accurate is it?  Everything you mentioned about rings and guides and break-in etcetera is true but how do you account for larger than engineered for displacements and higher than anticipated rpm motors? Also, stuffing a counter-weighted crank in a stock crank case has to take up some space right? 

[hotrodsurplus]

That's not entirely accurate is it?

I'm open to verified real-world information that runs contrary to that. I'm in this to learn.

Based on my experience it is accurate. The net displacement remains the same inside a VW engine as it runs. Remember, for every piston moving down the bore and creating a positive-pressure signal there's another piston moving up its bore creating a negative-pressure signal. Scaling things up by displacement or velocity shouldn't change that dynamic as everything increases proportionally.

If you want to get right down to tiny details increasing the bore diameter increases the amount of gases that get past the rings. But that's limited to the circumference increase which is pretty negligible. And that's governed by the percentage of gases that bypass the rings.

Jim Ratto brings up a good point about reshaping the case webbing. But that merely lets the fluids (air and oil) move about the case more freely.

Also, stuffing a counter-weighted crank in a stock crank case has to take up some space right?

Yes, the bigger crank does indeed displace more area inside the case. However, the volume that the crank displaces remains consistent.

I also have my own experience to rely upon. I'm no Roger Crawford but I've built a number of larger, moderate-performance engines for myself and others. For VW engines I never did anything more than route the breather line to one air-filter housing. I know that makes people shudder but I never suffered detonation from it or experienced much more than a slight oily film inside the housing. The only time oil ever came out of the crank pulley of a VW engine I built was when one pulley cracked.  The 327 in my roadster makes 344 horsepower just short of 6,000rpm and I run nothing more than a vent to the filter from one rocker cover and a PCV valve from the manifold to the other rocker cover. 

[JS]

I have had small breathing issues on my engines at high(7-8000) rpm. I hope not all of them have been badly built. 

Seriously, I think you need a little breathing when running a big engine at high rpm. We did Jim´s trick about opening up the passages in the case, seems like a good idea.
In my experience there´s a big difference from 6000 to 8000 rpm when it comes to the engine´s needs for breathing. I run only a Berg box with a hose from the fuel pump block off. No venting from the valve covers.

[Taylor]

Yeah but the motor was 327 cu.in. to begin with right?? Apples and oranges.   True or false?  A 96 cu.in. with 3% blow by leaks less air past the rings than a 139 cu.in. motor with the same % of leak down. True or false?  A 96 cu.in. motor @4000 rpm leaks less air past the rings than a 96 cu.in. motor at 8000rpm, leak down being equal. It's not all bad engine building

[Fritter]

Update:  I put on non vented valvecovers and the world did not end.   

I have a rubber tube going from breather tower to just above the choke to #1 carb.   It seems to be venting pretty good.

My only oil leak seems to be the rear main seal now....

I have an old Deano oil pump with 36mm gears on my engine, and I also am running 20w-50 oil....so next I will probably try lighter oil and a smaller (26mm gear perhaps) oil pump.  I do want to run the Deano oil pump, but I think it may be too much pressure.

[lawrence]

I run only a Berg box with a hose from the fuel pump block off. No venting from the valve covers.

JS, I have thought about trying this on my 1.9L. There is no oil seepage from my engine with both valve covers and the stock oil filler vented to a small breather box. I have considered only venting the fuel pump block off and the stock oil filler. I do not like the idea of oil leaving the rocker area during high rpms or extended freeway driving.

I wonder if there is a relation between frequency of valve adjustment, valve stretching, heat soak in the rocker area, etc., and engines that do and do not have hoses which vent the valve covers.

Cool Fritter. It seems like you may just have a bad main seal.

[Zach Gomulka]

I have an old Deano oil pump with 36mm gears on my engine, and I also am running 20w-50 oil....so next I will probably try lighter oil and a smaller (26mm gear perhaps) oil pump.  I do want to run the Deano oil pump, but I think it may be too much pressure.

That's huge! You could easily run 5w with that pump.

[Fritter]

Yea, Zach, it is a rather large pump!  I was surprised when I measured the gears and remember thinking "this is kinda big", but I put it in anyways because I like the old parts. 

I think I will try lighter oil first, maybe a 10w 30 or 10w 20 or maybe even 5w 30 or 20. 

[Jim Ratto]

I have an old Deano oil pump with 36mm gears on my engine, and I also am running 20w-50 oil....so next I will probably try lighter oil and a smaller (26mm gear perhaps) oil pump.  I do want to run the Deano oil pump, but I think it may be too much pressure.

That's huge! You could easily run 5w with that pump.

man what torsion bars do you run with that 36mm pump?



 

[Fritter]

The 36mm pump feeds the muffler bearings and also the bearing on the water pump, so I have to run it.   

It's funny, because the original Deano instructions I have say to run the shorted oil relief plunger and not the longer one, because the shorter one bypasses 15-20 lb earlier than the larger one, and they said if one used the longer one, the oil cooler may "swell".   So they knew something was up!   

I'll try 5w-20 oil next, the 20w-50 tar will be drained soon.     How did 20w-50 oil get popular in the aircooled vw world, anyways?  Probably by cheap-ass people with old worn out engines!

[Jon]

The large oil pumps (26mm) cavitate quite early in the rpm spectrum according to the latest research. This leaves the oil "aerated" on the pressure side, maybe we need the 50 oil to still have the oil carry the load.   

[hotrodsurplus]

In my experience there´s a big difference from 6000 to 8000 rpm when it comes to the engine´s needs for breathing. I run only a Berg box with a hose from the fuel pump block off. No venting from the valve covers.

Good point. The limit of my experience is engines running 6,500 or so tops. True, increasing the number of firing incidents in a given time would increase the amount of gases that get past the rings. Also super-fast engine speeds like that might induce crank flex that could compromise the ring seal. But as your experience shows, the ventilation needn't be super elaborate to solve the issue.

[hotrodsurplus]

Yeah but the motor was 327 cu.in. to begin with right??

That particular engine started as a 327 but bore and stroke aside it's no different than a 265. In fact Chevrolet made the breather system SMALLER when it adopted the 327 like mine. And my engine made 340 horsepower from the factory (the 265 with the larger breather system made 165 HP.

The 265, 283s, and real early 327s used a gigantic road-draft tube off the backside of the block. The ones like mine use a small breather in the oil-filler cap and a PCV off the back of the valley. If you had to breathe through that PCV you'd suffocate (provided it moved air in both directions). It just doesn't flow that much.

Furthermore, Chevrolet kept the same basic breather system through the 400ci engines and all the way to the end of the Gen 1 engine (265, 283, 327, 350, 307, 400, 305, 262). The early '70s LT1 engine used the same breather as a lowly 307 and the LT1 was capable of 6K+ engine speeds. Look up a photo of Chevrolet's highest-performance engine from the era (the L88 427) and you'll see the same size breather tubes and PCV that you'd find on a 327 like mine.

So in effect an engine with a 3.875" bore that spun only about 4,500rpm (265) had a breather system that had more capacity than the breather system on an engine with a 4.25" bore that spun 6,500rpm (or faster with the right prep). I see where you're coming from but understand that increasing bore size and/or engine speed doesn't automatically increase the need for case ventilation.

A 96 cu.in. with 3% blow by leaks less air past the rings than a 139 cu.in. motor with the same % of leak down. True or false?

False but not entirely. The circumference of the ring-to-barrel dictates how much potential leak area exists. An 85.5 bore has a circumference of 268mm. A 94 bore has a circumference of 295mm. That amounts to a 10-percent increase of potential leak area. The stroke isn't going to matter very much because the majority of leakage will occur in the first part of the combustion cycle. The pressure decay in the cylinder will prevent very much from leaking past the rings after 20 or so degrees of crankshaft rotation after TDC.

A 96 cu.in. motor @4000 rpm leaks less air past the rings than a 96 cu.in. motor at 8000rpm, leak down being equal. It's not all bad engine building

It's true that engine speed will increase the amount of gas that escape the rings. However, the issue is whether or not it's enough to overcome the breather system. The breather tube that Volkswagen used is considerably larger than the breather that GM used on its V8 engines. The PCV is simply tiny compared to a stock VW breather. The baffle in a V8 rocker cover restricts flow just as the louvered plate at the base of a generator stand. And the PCV benefits from the low-pressure area in the manifold only under low-load applications. Once the manifold approaches atmospheric pressure it doesn't exert a negative pressure on the engine case.

I fully admit that very fast engine speeds may increase leakage exponentially due to unforseen things like distortion but increasing speed within the range that most high-performance engines operate in or increasing displacement doesn't necessarily warrant a ton of extra ventilation.

[hotrodsurplus]

I have an old Deano oil pump with 36mm gears on my engine, and I also am running 20w-50 oil....so next I will probably try lighter oil and a smaller (26mm gear perhaps) oil pump.  I do want to run the Deano oil pump, but I think it may be too much pressure.

That's huge! You could easily run 5w with that pump.

Yeah, no kidding! A main seal can bear only so much pressure. Giant gears and thick oil have consequences.

Don't be afraid of really light-viscosity oil. I have 26mm gears in my 1600 and I run 5-20 all summer long (sometimes in triple-digit temperatures). Last time I checked the oil pressure was hovering just short of 50psi at freeway speeds. And my engine is no spring chicken.

As a rule of thumb an oiling system needs to develop only 10psi per 1,000rpm to reliably isolate the bearing surfaces from the journals. Any more than that and you're wasting power on the pump.

[Jim Ratto]

I would love to see a modification to case with additional breather opening in front of fan housing, just something simple like a 12-14mm nipple to attach hose to. Or a re-design of generator stand to include area where stock fuel pump bolts to case. Like a one piece casting that covers both generator baffle plate and fuel pump hole, with venting to atmosphere, air cleaners, etc. The 911 motor does use a good sized breather line, 25mm diam. Most VW's run 12mm. In the 1990's I was involved with a pretty stout 2386 drag motor, well known for its oil downs @ Sac etc. My boss at the time and I went through the motor and I suggested the case web contouring but no changes to puke box/lines. I was leaving line @ 8700 and shifting @ 9200 after we got motor together and no more wakes of green Kendall. Car now wouldn't leave and track straight.