There really is no such thing as "break in" any more. Back in the day, you would run a non detergent oil for a limited time to get the rings to seat. Ring quality is much better than it used to be, and non detergent oil is nearly extinct (or maybe it is by now). I give a new motor garage time, then open it up on the track. Break in complete.

   I agree with Andrew about the vast improvement in ring quality however I still do breakin the way I have forever.  Pull the distributor, use a drill and rod to spin the oil pump till oil pressure is up, replace the distributor,then fire it up and run immediately to 2,000 rpm for 15 to 20 minutes, then cool completely and run it again for 20 minutes at 2,000. Change oil and filter and you're good to go.  Main reason for doing this way is not to worry about ring seal but most cams are cast iron, not billet, and many of the cheaper cams are not hardened . A couple of heat cycles before you really load it up on the track is insurance against flattening the lobes.  Also, important to get the engine to fire as quickly as possible as this also is a cam killer.
   There's going to be a lot of opinions on this but my engines have  lived  doing it this way.  Good luck.

I haven't had a new cam in so long, I didn't think about the cam. You're right, cam break in is a MUST if it's a new cam, or if you've switched lifters. 20 min over 2000rpm, change the oil, and run it hard. If you can get your hands on a zinc additive, use it too.

Of all the motors I've built, I only lost 1 cam. I gave the owner the new engine to install and cam break in instructions. The cam went flat. When I quized him about the cam break in procedure he used, he went dumb. I guess he knew better than me.

its a good idea to run a oil  that has high zinc content or a additive even after the break in... i break my motors in about the same as the other guys have posted... except i run mine at different RPM's...

i'll run the motor at 2000 rpm for about 10 minutes, then drop it to 1500 for 10 minutes, then bring it to 2500 for 10 minutes... that way it gets a good range of rpm's... then change the oil and filter...

hey i would like a oppinion on spring preasure ................ had a cam go flat and ran the car one time , ended up tearing the whole motor down cleaning ,new bearings ,etc . cant remeber what my engine builder said the springs wer at @160 seat  , help me out here i no this is also a factor in cam run in or cam life period .

   Like Dave BauerSS6 I think 160 seat pressure on a flat tappet is too much.  Another thing some builders will do is to run 1.3 ratio rockers for breakin to lighten the load then switch back to 1.5, 1.6 or whatever  combo to race on.  Of course, it'll add several hundred bucks to your bill just like every upgrade you do to your parts.
   If you do your own engines it's about $160 for a set of 1.3 rockers from Speedway Motors and another few hours of your time. And like everyone says a high zinc content oil or an additive is really necessary on any flat tappet cam engine.  Again, cheap valve trains require more care and protection.  Read a report on this years ago and the varience in Rockwell hardness on some number of cams checked was surprising.
   A lot of cams are destroyed in the first 5 minutes of run time and it sure ruins your day and lightens your wallet.

Flat tappets should never have more than 130 on the seat...

COMP Cams makes an additive and I believe they send it with their flat tappet cams nowdays.

Racing oils like Brad Penn or Joe Gibbs still contain Zinc (i believe)

They sell lucas break in oil for around 10 bucks.  I'm thinking of running the break in oil every oil change.  Seems like cheap insurance.