Crankcase vent


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By DANIEL TINDER - 17 Years Ago
In a previous post, charliemccraney installed billet breathers in valve covers. Has anyone ever tried putting one on the block hole? If they come with a baffled grommet, would high rpm crankcase pressure likely still force oil out if pcv AND vented oil cap were also utilized?

I used to run a more effective oil cap filter (and restricted pcv valve vacuum tube.... ran too lean otherwise) on my T-bird with stock block-off plate, but hard driving would force the dipstick out, and the oiled cotton breather cap filter would drip oil. Wouldn't the additional block breather be advantageous by bringing in air from lower down for move complete evacuation, AND eliminate the bottleneck that allows crankcase pressure to build?
By PF Arcand - 17 Years Ago
Daniel: Interesting idea, you could probably make an adapter plate & use a curved up breather on it, as long as it is baffled enough to avoid oil loss. Should work fine & look much better than the canister setup.
By Ted - 17 Years Ago
The road draft tube has breather capability and is already filtered as well as having a built in drain back.  I put one of these on the Engine Masters Challenge engine that was put together last year for the extra venting that’s afforded by a breather in the crankcase area.  But total agreement that something else would probably look better and be less cumbersome.

The Y doesn’t have very much venting in the valley area to relieve crankcase pressure at full throttle without putting additional holes in the valley so extra venting at the outside of the block can be of benefit in a performance application if not running a vacuum pump or header evacuation system.  I run the evacuation system on my roadster but this type of system works best with open headers and not very well when the exhaust system has mufflers.  If running a PCV valve, then the venting at the block is going to be counter productive to the operation of the PCV if wanting to run a negative pressure on the crankcase in normal driving.  If putting an external vent in this area, then it’s going to be important to have the filter itself up quite a bit higher to keep oil from blowing out of it.

By DANIEL TINDER - 17 Years Ago
If running a PCV valve, then the venting at the block is going to be counter productive to the operation of the PCV if wanting to run a negative pressure on the crankcase in normal driving.



Don't quite understand. I realize that hot, blow-by fumes naturally rise to the valley area to be evacuated by PCV/oil cap draft in late OEM set-up, but why would crankcase air source be counter productive? If oil cap filter was restricted to produce the same combined CFM ventilation, wouldn't the same degree of neg. pressure still exist for normal driving? Or does higher crankcase pressure cause oil occlusion of vent? Am I missing something obvious?