340 break in question

Rusty is correct. Its OK to rev it up and down during the process, 2k being the minimum RPM. We've had to stop during break in for many reasons, distributor failed, leaks, etc and finished the break in and never had a flat cam. There has only been 3 flat cam in all the engines my dad and I built, one was my 340 with the guides to tall for the cam lift, (one of our first builds, lesson learned the hard way and I'm proud to say the 3rd revamp of that engine fired up this fall with no issues or leaks). The second was a 350 for a friend and he said he would break it in, well one happy 600 Double Pumper with incorrect float height or too much fuel pressure later whipped the cam out with fuel dilution. The 3rd was in my dads 390 Ford, and no reason found for that one, Comp Cams replaced the cam and lifters for free, this was when they had a bunch of junk lifters in the mid 90's.

New oil with Zinc, pre-oil and fire it up. 2-5K for 15- 20 min. Fan in front of engine.