We ran limited vacuum as well in the system with an adjustable valve. 12"HG for us and we monitored it with the data system. Real high vacuum in the crankcase with wet sump oiling and pump in the pan, the pump is working against the vacuum. Our Moroso consult felt the 12" HG was a safe max number for a stock Melling pump which we were running at the time. He mentioned the dry cylinder wall and pin oiling issues at high vacuum, but didn't really believe it was a factor nor did he have any hard data. I tend to think that's mostly speculation as well. When you have a guy like Langer running 19" HG at speed with no issues, at what I assume is high RPM's, that tells the story IMO. Picking up vacuum from the front of the valve covers for drag racing seems like a fine idea and worked for us through a baffle system. For our road race engine, picking up in the center, inboard, high in the cover I like because of the high acceleration forces as well as high braking forces. Nice compromise.
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