PCV valve and breather with vent necessary?

[bosshoff]

Do you have to run a PCV valve piped back to the carb? Also, the vent from the oil cap filler to the carb? If I were to run simply a vent cap on each valve cover, would this affect my engine negatively in anyway? (This is not an emission question)
This is what I am thinking.

 

[carmi]

Part of the benefit of a PCV valve is that it sucks moisture from the crankcase that results from the heating and cooling of the engine. While a vent may keep the engine from having positive crankcase pressure, and damaging seals, I don't think it will be nearly as effective at drawing the moisture from the internals of the engine.

 

[Viperwolf1]

The PCV valve is good for eliminating moisture and fumes from the crankcase. In order for it to work you need to allow fresh filtered air into the crankcase somewhere. That is why the stock valve cover vent hose went to the air cleaner.

 

[blubuckaroo]

A PCV system is the best thing you can do to keep sludge from building up in you crankcase.
The valve is not just a check valve. It's pretty much a metered vacuum leak, and needs to be selected for your engine's particular vacuum.
A regular valve cover breather cap will work with a PCV system, but it will need to be cleaned occasionally, and tends to drool onto your valve cover. A breather hose to the air cleaner is cleaner and needs no maintenance.

 

[bosshoff]

Got it guys, thanks. I just switched carbs from a 4 barrel to a 2 barrel. This meant I also had to switch air cleaners from 14" to 13" due to clearance issues. The new cleaner will need to be modified to accept the fresh air vent hose. I will do so.

 

[Steve83]

This caption explains the hows & whys of the PCV system: