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vent?

Not to argue with Ron, but the air flow in that top vent already goes both ways. The metered orifice attached to the small hole in the valve cover draws a slight vacuum on the entire crankcase. This vacuum is relieved through the "big" hose with filtered air from the inside of the air filter. When crankcase pressure, usually from blowby, builds to put an actual pressure in the crankcase, the big hose allows this excess to vent into the air filter and into the motor to be burned. A lot of guys with higher mileage motors notice the oil in the carb asa result of this.

With good fittings on both ends, good hose in between, and clean screen inside the valve cover this should be enough vent to keep the pressure from building. If you do want another vent, for whatever reason, I think the side cam cover in the head would be a better choice than the fuel pump block-off plate. It is much higher in the motor, and being steel might be easier to weld a stand-pipe or something to.
 

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old motor tales.

Back in college, when I ran around in an Opel with a LOT of NOS, I had a lot of issues with crankcase pressure. What I ended-up with was a piece of 3/4" conduit about 6" long with a slight bend on the bottom so that it came straight up but angled into the cam cover. On the bottom of the tube I added a 3/8" nipple going straight down. A hose was then run from this barb to one screwed into the extra dip-stick hole in the oil pan. I just had a little K&N filter on the top, but it would be very easy to route it almost anywhere if desired. Usually the extra oil drained to the pan, but if pan pressure got excessive it would relieve up the tubing and any entrained oil would fall into the side of the head instead of going up to the filter. That stand-pipe did a lot to keep the oil and pressure issues to a minimum, enough in fact that any time I build an Opel motor for real performance I'll definatly be incorporating the feature.
 
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