that links nicely to this old thread:
Let's talk about bearing clearances - SR20 Forum
"...Other tests have shown that the Counterweight center of gravity and actually different weight counterweights (on a 4 cyl crank) yield far better dynamic balance than the "eye" pleasing perfectly symetrical 8 counterweight crank.
These studies were initiated by the NASCAR guys who had perfect correlations of wear patterns on two specific main bearings, regardless of bearing type, oiling, brand etc.
The original Porsche 928 V8 had a simillar problem, traced back to the inlet manifold design..........same problem as on a 4 cyl where #3 and #4 fire sequentially......the low pressure on the inlet of one cylinder (because one right next to it just sucked all the air) alters the in-chamber pressure at TDC on the next adjacent cylinder..........the combusted "gas effect" translated to wierd behavior on the crank journals of the two. They cured it by changing the configuration of the inlet manifold.
SRs like to kill #3 Main right, 3 fires before 4. 4 is starving for air as 3 just sucked the air at the entrance to the port runner. Now 4 fires, 3 is on ex stroke and has the highest rod loading in tension as it is pushing gas through an open system. 4 completes the combustion stroke while 2 has been in compression. 3 and 2 are sharing the same main journal (#3) and has a compressive load on one side (2) and a tensile load on the other (3). The effect is quite possibly detrimental to the #3 Main Bearing.
Only guessing as it's hard to prove on the SR. Been seen and proven elsewhere though."
Something to think about.
Mike