Freak,
Break-in is absolutely crucial to the life of a camshaft. If you don't do it right, you greatly increase your chances to flatten a cam lobe.
I like to break in a cam like this:
- Be sure that the cam is installed properly, with the proper cam break-in lube
- Use a known induction setup- in other words, don't try this with a new setup (a new carb, etc., that you aren't sure it is tuned properly). If you are going to switch to a new carb, do that *after* break-in so you don't have to stop halfway through and risk ruining your cam
- Start the motor and set the timing at idle (as quickly as possible)
- After the thermostat opens, top off the radiator and put the cap on (don't try the break-in without the cap)
- Raise the engine speed to 2000 RPM and hold it there for 20 - 30 minutes
- If you are going to use a mechanical fan, that should be "okay" for cooling- if you use an electrical fan, you should keep the radiator cool with a garden hose (electric fans will not keep the engine cool at 2000 RPM)
- Have a second person around just to keep an eye on things- make sure no oil is dripping, make sure your radiator doesn't start to overflow, watch a clock, etc.
- A couple times vary the engine speed- I like to keep it between 1700 and 2300 RPM
- After you've run for 20-30 minutes, shut the engine down and don't touch it for 12-16 hours
That procedure will break in the cam. To properly seat the piston rings, you will need about 500 miles of driving. Best is a heavy load about 2000 RPM, for example climbing a mountain. Vary the engine speed during this driving, as you would during normal driving (don't just get on a motorway and go straight for 500 miles at 65 MPH).
Make sense?
-Bob Cunningham