Jeezus are you kidding bustert? The carbon buildup it causes has been well documented and so has the hp loss. When that carbon build up gets hot enough and starts glowing red, guess what happens next? Or keeps a valve from closing. I've seen the inside of motors that looked that bad and worse venting internally. But vent where you want.

Carbon build up external venting vs. venting to intake

Aaron Wilson, awsracing, also did extensive testing, 100s of dyno pulls, on different breather systems and the ONLY thing that made a difference EVERY TIME as far as power was concerned was getting it out of the intake tract and venting to atmosphere. Maybe only 2 or hp but across the entire rpm range. And it's not the power loss itself that's concerning.
Then there's the issue of it contributing to already hot running motors. Maybe not an issue for your `74 IH that doesn't make enough power to get that hot and comparing an air cooled v-twin to a multi cylinder water cooled industrial engine that has pistons going down as well as up at the same time not 2 going up and down nearly simultaneously? Why do you think automotive pcv valves dont last very long in a Harley v-twin?

 

Results like this are everywhere with a simple search. Venting to atmosphere is a must if you give a **** about your motor more than the epa. 15° drop in oil temp is huge. Not sure why anyone would want to breath hot, oily air into the combustion chamber instead of cool, dry air.

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