vent crankcase to carb

[doc73]

Would there be any disadvantage to venting the crank case to the bottom plate of my Kadron? I did have it vented to the top previously but I am changing the hose and the fitting. Was hoping to stream line the appearance in the area and it would look cleaner if the line could go to the bottom plate of the carb.
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[FeelthySanchez]

Assuming dual Kads, not a great idea mate - as the vacuum signal @ carb's base is very strong.
By comparison, the normal crankcase breather hose-to-air-cleaner "hat" or top plate has virtually zero vac. Simply stated, the engine would likely respond as if a large vac leak were present - but only upon the side where the breather vent hose was plumbed to the Kaddy. Probably best to utilise a tee arrangement & feed both Kadds equal portions of that nasty ol' crankcase stank.
Hope 'dis helps a bit .......
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[Glenn]

I'm not a fan of venting to the carb at all,
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Glenn
74 Beetle Specs | 74 Beetle Restoration | 2180cc Engine
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#BlueSquare

[EVfun]

If you mean the bottom plate of the air filter then that is fine. The air filters that came with my Kadron kits years ago had the crankcase vent line there.
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[doc73]

Glenn you mentioned that you were not a fan of venting to the carb. Why? Didn't VW have a factory set up plumbed in this way?

And yes I was asking about venting to the bottom plate of the air cleaner, not the carb itself.
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[Glenn]

I'm not a fan of dumping oily air down the carb.
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Glenn
74 Beetle Specs | 74 Beetle Restoration | 2180cc Engine
"You may not get what you pay for, but you always pay for what you get"

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[esde]

[ps2375]

Oily air tends to reduce the effective octane rating of the fuel for the cylinders that it is going into. So, if you do it to a motor with a single carb, they all get the reduction, if you do it to a dual carb motor and only on one side, half your motor feels the effect, either way, bad and worse.

[doc73]

Ps2375- thanks for the input. It makes sense and now I guess I should be looking into a breather box.
A - one that mounts to the alternator stand
Or
B- a remote breather box with a Hose going from the stock oil filler neck to it

Any input to pros and cons on either of these is greatly appreciated.
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[nextgen]

Ok here I go playing the Devils Advocate. Lets talk average engine not race engine. How much oil do you really suck in, it is only a mist in a stock engine. As for dirty oil, damn if oil that is in that mist is dirty, meaning particles, better change your oil more often or get a real filter. It the engine has a blow by issue because of age, sure you can foul your plugs. As for damage, I would not think so seeing you are actually lubing your valves and cylinders. Think Diesel, why do they last so long, we are talking 22 to 1 compression in a VW Diesel that is stress and they last forever. The reason is they burn oil and are constantly lubricated. The air filter is large enough to allow enough air to come in and not increase the the volume of mist from the crankcase. If you are getting a really heavy blow by effect it is time for rebuilt, but actually the blow by may keep it running longer.

Granted, the air filters get oily and get ugly. I have K&N they need to be oiled anyway.

So I see no real problem, if you do a breather box or directly into the case again, or ail filter .
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[vwracerdave]

The stock engine came with an oil bath air breather. When you vented the crankcase to the factory oil bath air cleaner the oil was separated from the air stream going into the carb. An aftermarket paper or gauze element does not separate the oil that enters the carbs.
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[Eaallred]

[mark tucker]

oil mist/vapors can cause detonation and carbon buildup as well as funk in the intake tract . not a good idea

[Lingwendil]

[nextgen]

Mark I agree and yes what you said is worst case scenario. I said you can get fouled plugs that can also cause the other symptons, but the oil is not dirty oil.

It is the same oil that is blowing by all our cars rings as we drive every day and gets into the same combustion chambers, especially as our engines age and wear.

After all the VW engines I have rebuilt since 1965, I come to this conclusion on combustion chamber carbon build up. All the engines that had carbon build up were ready for a rebuild and worn out. Usually the heads were loose. Also as for the carbon build up, was it oil or running too rich. Black smoke, is rich mixture, blue smoke is burning oil.
Running the crankcase oil mist into the air filter will have little effect on an good running engine that is not in bumper to bumper traffic on daily commutes. When I say good running I mean properly timed and most of all a good ignition spark. Electronic High Voltage ignitions are the best defense against fouled plugs and carbon build up.

Does running a breather hose into the air filter create carbon build up, maybe, but not enough to worry. Is is better to just run it back into the case yes.
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[modok]

open the can!
To be fair, we all probably should vent to the carbs, so we aren't polluting the atmosphere, making sad polar bears or whatever.
But like anything, best to do it right or not at all.
To keep the oil mist out of the intake, you need a good mist separator.
A breather BOX that actually does a good job of removing all mist. If you do make a remote box that does do a good job of removing mist and draining it back to the engine, then it will also do a good job of retaining water vapor and draining it back to the engine, so, now we have another problem.
Now we need PCV, to move air through the system and take out the water vapor. IMO, if you have duals and lack strong steady manifold vac to use a regular PCV valve, it would be most practical to use a one way valve, like a "crank vent" to keep the air going the right direction, put the IN on the 3/4 side, and the out on the tower and 1/2 side going to a good mist separator, and then into a the carb filter.
Surprisingly complex to do right, so instead we just keep it like it's 1965, and lubricate the road a little, and nobody really gets hurt right?

[doc73]

Ok you guys have provided great info but now I'm lost. My set up uses the stock oil filler on the alternator stand that has the fitting for the hose to the carb. If that port is not vented or plugged it will spit oil out. I vented to the carb originally but I know now, that is not ideal. For my set 1776 w/ dual Kads what is the most practical set up:

A - breather tower(like a berg unit)
B - or remote breather

Engine runs fine and I dont have a lot of excess oil blowing around I just know if I don't vent the crankcase I will get more oil out through that spot.

Thanks again.
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[74 Thing]

Vent into a breather box or oil catch can. It is not that expensive and solves your problem.

[nextgen]

Modok, funny that was the first emission device. Hose into air cleaner, then came the PVC valve. Now we have HAL from the Movie 2001.

Simple but in a normally aspired Rabbit Diesel you can die from direct Crank Vent to Case. Diesels do not have and ignition to shut and even if the FI was off it will still run from the mist.
Happened to me the Engine ran away, it thought the mist was fuel and my car went from 60 I went to 90 and climbing. I knew if I shut it off and turned the key all the way the steering would lock so that was out. Lucky the road was clear and then it went back to normal and I was able to shut it down safe. Called the dealer and they said it was a big recall and several engines blow when the owners put them in natural.

They gave me a check valve gizo, done.
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[EVfun]

A positive crankcase vent would help prevent condensation in the oil, usually seen as a tan to gray slime inside the oil filler. With an F.I. system it would be easy. Put a little air filter as an intake at the fuel pump blockoff. Modify the factory breather/oil filler for a grommet. Plug a pvc valve into that and plumb it to the center of the intake manifold. It should eliminate the crankcase condensation and any blowby around the pulley.
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