Quote:
Originally Posted by Jay S
I am sure you are correct on that. Maybe flaking maybe isn’t the best wording. Gulling might better description, all I can do here is try to describe what a nitrided cam looks like when it fails, and why it fails. Or why I think it fails. 
The hard shell on the surface from Nitriding is 3 or 4 thousands thick with current Nitride process’s on cast cam cores. Below that thin thickness the Rockwell hardness drops below what the cast core was originally. I can’t remember how much, something like 15 c scale. The surface hardness goes up by 15 or 20, putting the hardness 50 or better, but below that surface it drops to 20s to 30s. For reference average core hardness of most cam core is suppose to be in the lower 40s. These days it is more in the mid 30s. Nitriding is great for cam break in, then eventually with use the shell gets thin and it pulls small chips off the surface because the metal under that surface is extremely soft. Then the lobe gets wiped. Most off the shelf cams are cast of Proferall. Often the lobes are a little narrower on off the shell hyd cams using the basic Proferall cores. Solid cams are usually Proferall+, a bit better cores, and slightly wider lobes. Multiple aspects to look at for better success on cams with nitriding. Personally I would not bother nitriding a typical off the shelf cam with out a least looking at the core used for the cam.
Nitrated cams with tool steel lifters is very common on flat tappet restricted racing, all racing categories. Some jump up to p55 cores, which do not seem to like nitriding. Most don’t have $ in the budget for the billet or tool steel flat tappet cams. |
I have dealt with nitrided engine components in automotive and aviation applications my entire adult life. I have never seen a properly nitrided component fail. I am not saying it can’t happen, but I have never seen it. In aviation we used hardened face valve lifter bodies. . We had horrible problems with cam lobes spalling, pitting and eroding due to inadequate oil supply. Splash oiling is the norm for the cams in aircraft recip engines. Currently, there is an STC that provides an oiling port for each cam lobe through the cam( most aircraft recip engine cams are forged steel and hollow).