I have a new set of drilled and slotted rotors for my front disk brake conversion on my 68 vert. The rotors themselves are not directional, that is the cooling vanes are straight, not curved. But the rotor slots are opposite on each rotor, meaning that they will either both intersect with the brake pad at the outer edge of the rotor first when running forward, or both intersect with the pad towards the center of the rotor first. Which direction is correct?

Baer does them so the slots intersect the brake pad outer edge first.
In the Can-Am days, Team McLaren did it the other way, go figure!

Like the old saying goes - when you're out of slots, you're out of Baer....

I still have beeer.

Sounds like Mclaren might be on to something, though Baer is no slouch.
Should the heat be directed inward or outward? i would think outward.
Seems to me that outer edge first directs it inward, though i have no tests, and i sometimes think backwards.
Glad i could help ;)

I still have beeer.
Should the heat be directed inward or outward? i would think outward.
;)Heat is blown inward.

The idea of curved vane rotors is to direct the brake away from the tire bead. Wheel becomes hot, tire bead melts, tire goes flat, the end of your day. This is why you grease the bearings with high-temperature grease, the bearings and other items can withstand more heat than a rubber tire.

http://www.stoptech.com/tech_info/img/rotor_drilled_cutaway.jpg

If the air is supposed to go from the outside in, I wondered why all the cooling kits I'd seen direct the air to the center of the rotor. The picture is from the Stoptech site showing the curvature of the rotors going rearward which would conduct heat from the inside out.

http://www.stoptech.com/tech_info/faqs.shtml#16

what Everett said makes a whole lot of sense.

The vanes in the Stoptech pics looks like they scoop air from the front center and bottom, directing inward, and release air/heat back from center outwards towards the rear from bottom up and around.

But then again, i still have baer... err... beer.

And maybe vane configuration can depend on caliper position too?

As shown in the picture, the right side rotor turns in a clockwise direction and the left side rotor turns in a counter-clockwise direction. The air is conducted from the center outward. If you add a brake cooling duct, the cool air from the duct goes into the center of the rotor.

Those rotors look backwards to me. We're looking at the inside not the outside. The air is moving in. Not that I know about this or have an opinion on what's right, I'm jus lookin at da pictures!

The picture is correct and is viewed from the outside of the car. The vanes are acting as a pump moving air from the center-out.

Here's some pics with the ducting and directional rotor installed.

http://freeweb.siol.net/anddrej/Razno/Installation%20of%20Front%20Brake%20Duct%20for%20a n%20E36%20M3.pdf#search=%22brake%20rotor%20duct%20 picture%22

Yep, the fins work just like a water pump impeller.

I guess I've been educated.

Thanks for all the info guys. After much research from various "experts" I have come up with the following. If the rotors cooling vanes are directional, they should rotate so that they pull air from the center and expel it along the outer edge of the rotor. Such a rotor that is slotted will have the slots cut so that they curve the opposite way from the cooling vanes. This is so that they do not overlap a vane and create weak spots in the rotor. Cutting the slots against the vanes will provide much more strength as multiple supports between the vanes intersect with each slot. The general opinion seems to be that if the rotors are not directional (which mine are not, they have straight vanes) the slots should be cut so that the pad contacts the slot closer to the center of the rotor and the pad dust us directed outward. Now, I think I need a beer!