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vocal opposition to them, but let it rest until I had more information. I did not run the pulley specifically to see if there would be damage - at the time there just wasn't any conclusive evidence or people willing to test it. In my first build I did not use an underdrive pulley - I used an OEM harmonic dampener/pulley and did not see any signs of wear on any of the bearings, even after some 35K miles of HARD driving. I ended up destroying a piston because of severe detonation due to a damaged valvestem seal that my machinist at the time screwed up on installation - and then after rebuiding it that time, I still used the stock pulley - then setting a record 413RWHP on stock turbos and beating the daylights out of the engine for another 20K some miles until an EGT probe went to pieces - destroying the driver's side turbine as well as blowing particles into the driver's bank cylinders and pitting the pistons and combustion chambers on that side. Even with all the abuse to that point, I did not see any wear on the bearings of concern and if it weren't for a 'matter of principle', I would have been able to re-use those bearings again. I didn't use an underdrive pulley until the rebuild at that point and I did use new OEM bearings once again, and now we see these interesting wear patterns. This is not from oil starvation either since there are 4 points of oil entry into the crankshaft at each main journal. If there were starvation, we would have seen all of the bearings showing excessive wear - as I have seen several times before on engines starved of oil. Without a harmonic dampener on the crankshaft, the crankshaft will twist every time a piston fires. When it twists-up, it will un-twist and rebound - then you have a crankshaft that is ringing at its own natural resonant frequency. This 'harmonic' frequency of vibration causes the connecting rods to 'rattle' on the crank pin where they are connected. The bearings take this beating which will lead to excessive wear and eventually complete failure. The harmonic dampener absorbs this vibration so the rod bearings dont have to. Obviously the theory is only attempting to support the observation - it does not mean the theory is correct - but at this point it is only the best explanation for the evidence.
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