Originally Posted By: burla
This is the kind of thing happening over and over with hemi tick. One lob gets wiped out, thus turning into a 7 thousand dollar dealer fix. Hemi tick leads to wear here, downstream at the cam!! The other forum has been testing now nearly 5 years.
That's a Selectively Austempered Ductile Iron Cam Core (SADI), This material IS NOT suitable for Roller Cam applications, Even after the hardening process.....The work surface is still cast iron!!
In the 90's some budget aftermarket (Retro-fit) roller cams were SADI cores, Failure rates were VERY high, I can't believe an OEM manufacturer would use this in their "flagship" engine.
I know for a fact....When the 3rd gen Hemi came out in 2003, They used a multiple piece 5150 steel alloy camshaft (The Lobes were separate from the center core) which was a cost cutting measure of it's own as they didn't machine a solid billet blank. I'm guessing only the newer year models are affected (When they changed the camshaft material)?
This is materials issue, I don't see how changing to a different oil will prevent failure??
I read some patent info on the SADI process, I found this very interesting......
"The advantage of camshafts formed of a ductile cast iron composition made according to this process is evident from stress and wear comparisons. A test fixture was fabricated to simulate engine operating conditions. Sample camshafts were installed in the test fixture and cycled at 545 revolutions per minute (RPM) through several 100,000-mile test simulations. Valve springs were used having loading characteristics which imposed a variety of stresses on the camshaft lobes. Tests of camshafts 10 made of austempered iron according to the invention will sustain Hertzian stresses of approximately 253 KSI without exceeding a 0.002-inch maximum lobe wear limitation. This endurance stress limit proved to be higher than those for camshafts made from either martensitic ductile iron or conventional 0.5% carbon steel alloys"
0.5% Carbon Steel Alloys.....This could most likely be considered 5150, They are basically stating that SADI has better wear characteristics. To bad in the real world this is not the case.
545 camshaft rpm equals 1,090 engine/crankshaft rpm, What engine runs at such a low rpm? They never stated what the spring pressure was during the test (Most stock roller cam engines run at least 170# of seat pressure with the valve open)