What things could happen to a camshaft that warrant its complete replacement?
There are couple of things which I can think of off the top of my head:
- Performance Gains: The user wants some gains in performance so will replace the camshaft so the engine can breath better (more air in = more power out).
- Cam failure: A cam can fail for many different reasons
- Cam lobe failure due to lubrication issues or failed lifter
- Cam bearing journal failure due to lubrication issues
- Cam breakage (I've seen this happen due to a warped head)
For the different ways that a camshaft can fail/break, are there any techniques out there to salvage a damaged camshaft?
If a cam is wiped out (cam lobe failure) or bearing journal failure, you can have the area rebuilt (welded) and ground down to spec again. If a cam breaks, you don't have much of a choice but replacement.
For almost any of the more common engines these days which accept performance improvements, there is most likely a camshaft design for you. There are many different aftermarket cam manufacturers out there who will build a camshaft to your specifications. They will also help you figure out exactly what is going on with a different cam shaft which will be right for your application. They can even build to suit. In most cases it's going to be easier/cheaper to buy a new cam than it would be to have your cam shaft ground down with a new profile ... that's most cases.
There are always the odd-ball engines which don't have an aftermarket which you'll need to do some extraordinary means to accomplish your goals. One of the ways which used to be utilized to see performance gains was to regrind a cam. That process would be to utilize a stock cam and regrind the base circle of the cam. The base circle is the where the lifter rides when there is no lift applied to the valve. If you grind this area down, the lift from this portion to the top of the cam lobe becomes a larger distance, and thus you have more lift and more potential air flow going into the cylinder. With so many good aftermarket cam manufacturers out there and the ability to have them grind pretty much whatever you want, this procedure has pretty much fallen from favor. Machining costs are greater than what something from a cam manufacturer would cost, so why go through the hassle.