Is It Better To Not Have Oil Breather Cap Fed Into Air Cleaner?

[boboh1]

My stock 383 has the air cleaner connected to the push on oil filler breather cap. I was thinking that cold air to the carburetor would be best for performance so would it be better to buy a regular breather cap and disconnect that hose leading to the air cleaner?

 

[lewtot184]

I don't think the breather attached to the air cleaner has any adverse effect; especially if the engine has good ring seal and the pcv is good.

 

[gkent]

The carb is always drawing "fresh air". I would think that air would be at least as cool as you'd draw anywhere else. If the air cleaner is sealed to the hood like any of the cold air systems then that's where you'd want to draw the air from. But in all likely hood if you were to measure the temps inside the engine it would probably be a negligible difference regardless or where you draw it from.

 

[Bird 426]

The breather is the inlet air for the pcv valve. No air should be drawn in at all.

 

[boboh1]

OK. Looks like I got my flow mixed up as air is drawn into the breather from the air cleaner and not the other way around so not hot air is going to the carb. I corrected my earlier comment mistake. Thanks

 

[eldubb440]

if the engine is heathy, air is sucked into the breather, not out

 

[gkent]

Air is drawn IN through the breather. Air is drawn OUT through the PCV by manifold vacuum. Since much of the crankcase volume is from blowby, just how much air is drawn through the breather is questionable. More often than not there is oil spray around the breather which would indicate there is at least some pressure being blown out there. That said, the breather seems to be there more to ensure a balance - no vacuum or pressure in the crankcase. Pressure would have oil blowing out the front and back main seals. A vacuum would probably result in oil being drawn past valve seals, the PCV valve, etc., resulting in fouled plugs, carbon buildup on piston tops, valves and combustion chambers.

 

[Runner 68]

OK. Looks like I got my flow mixed up as air is drawn into the PCV valve from the air cleaner and not the other way around so not hot air is going to the carb. Thanks

Air is actually drawn OUT from the block through the PVC into the carb, not in. The intake is through the breather on the valve cover. Preferably the intake breather is catty corner from the PVC on the valve covers.
Breather driver side front end of the valve cover, PVC rear of the passenger side valve cover. Not a hard and fast rule but ideal.

Think of the block as a passive air compressor. Air comes in and has to go out. No flow, you start blowing gaskets, rear main seals etc. The more ventilation the better. A hose from the PVC to the air cleaner helps that much more by a positive sucking action removing the compressed air and recycling it through the block.

 

[Daves69]

OK.

Some reference info if interested.............

https://www.mymopar.com/downloads/mtsc/270.pdf

 

[boboh1]

Interesting read. Thanks for the link.