Valve cover breather

[g260]

I have replaced my standard aircleaner with after market sports ones and as a result I can no longer attach the breather pipe from the valve cover to the cleaner. I have seen pics of engines with a small K & N type filter on the valver cover and was wondering if this is ok. When doing a search on the subject, there seems to be differing opinions on how effective/appropriate these are as compared to a seperate catchment tank or just leaving the breather pipe open.

Any advise would be appreciated.

Thanks,

Geoff

[lan240]

If you install the k&n filter to the valve cover or leave it disconnected you will have a problem with fumes entering your z

[Royce]

If you are racing you should run the breather to a catch can w/ breather. Otherwise you could use just a breather but as lan240 says if there is a worn o-ring, gasket or seal somewhere on your firewall you can end up smelling fumes in your passenger compartment.

I have also heard that having the fumes drawn out by vacuum from the carbs helps keep the oil cleaner. This theory suggests that you are getting vapor contaminants out of the engine. This may be true but I don't know if it is significant. Of course if you have that many vapor contaminants in your engine you may be due for a rebuild anyway.

Hope it helps!

[morfirst]

I ran a flexible clear braided hose from the valve cover to a plastic "tee" hose fitting. Off of the "tee" I ran two short lengths of hose to two "90 degree" plastic hose fittings that terminates on the metal back plate of each individual carb air filter. The down side to this is that you should rountinely check any carbon residue buildup within the fittings. I have had this setup for 6-7 months, so far it works great without any significant build up. I believe the "tee" fitting has a 1/2" inlet and two 1/4" outlets. In my opinion, it looks pretty good.

[Royce]

Sounds interesting, how about some pictures?

[Dan Baldwin]

You'll love this. I just zip-tied a small piece of cloth over the opening. Cheap and easy! No fumigation problems. Also, there should be next to zero vacuum in the air filter at all times, since it's upstream of the throttles. It's the crankcase PCV that goes to the vacuum side.

[Walter Moore]

I would have expected the breather pipe on the valve cover to be an air inlet.

The PCV valve is bolted into the intake manifold, and connects to a rather large pipe on the side of the block. Having taken the engine apart, I noticed that there is a baffle inside the block near that pipe to prevent pulling oil up into it.

I just assumed that the air flow was in through the top and out through the pipe on the side.

Or have others disconnected the PCV valve?

Now I am really confused...

[Ben]

Walter, you are correct - the air is ingested from behind the air-cleaner & then the fumes are drawn out under vacuum through the PCV valve to be burnt.

If you plan on altering this setup, then you should put on a catch-can w/overflow.

[biker]

Does anyone have a photo of a catch can setup and where they have located it (without removing the battery from the original site).

I changed my breather to a K&N filter and have noticed some new oil smells of late. But since I have just completed some work underneath, I am currently waiting for things to settle down/burn off to see if the smells remain.

[Walter Moore]

Ok, I see where the fume problem comes into play, if you replace the PCV valve system with a breather then you have crankcase fumes blowing through the engine compartment.

But if you only replace the hose from the valve cover to the stock air cleaner with a filter on the valve cover itself, and leave the PCV valve stock, then there really shouldn't be any engine fumes escaping. (Ignoring the exaust system...) As long as there is a hose from the block to the PCV valve, you are still purging the engine into the intake manifold.

Or am I somehow still missing something?

[Ben]

theoretically, yes....

But some of the crankcase fumes end up coming out the rocker cover breather as well.