| I've been running with an UR pulley since mile zero, making some 678FWHP and 637FWTQ, rolled 83K miles the other day. I went through a series of rod bearing replacements every 15K miles as rod bearing failures are the biggest weak point in these engines, however, after going to heaver weight oil and shimming the oil pump relief valve, I am no longer seeing the bearing wear that I was with the thinner oils. I am still running the UR pulley. The thing you have to consider is the firing order of our engines. They fire straight down the crankshaft. Dampers are used to absorb torsional rebounding of the crankshaft resulting from the deflection it experiences at each power stroke. This torsional "ringing" destabilizes the oil film between the bearing and the journal and allows for bearing-journal contact and will destroy bearings in short time. Because our engines fire straight down the crankshaft, 120 degrees into cylinder #1's power stroke, cylinder #2 begins its power stroke thereby preventing excessive torsional harmonics from being created. This process follows through each consecutive power stroke to #6 and then the cycle repeats. There is still crankshaft torsional deflection but because of the firing order the torsional harmonics are dampened enough that we aren't wiping out the bearings. Different engine designs have different harmonics - different cylinder numbers, different firing order, crankshaft length, modulus of elasticity; all play as factors into the kind of torsional harmonics a crank will experience.
Enthusiasts soon understand each other. --W. Irving.
Are you an enthusiast? If you are out to describe the truth, leave elegance to the
tailor.
Albert Einstein
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