Interesting, I thought if it faced the firewall, it would draw a vacuum as air passes it. Which would combat the vacuum at the road draft. Face it forward and there is a slight "ram air" effect, adding to the vacuum made by the road draft. Anyways, it's a product of its time and it did work. You really don't need to be moving that fast to pull a vacuum. Pcv's came in for emissions, not because the road draft was not effective. If my engine was old, I'd probably fit a pcv just to manage the blow by and eliminate the stink when stationary.