The 30psi at 800rpm is the oil pressure generated by the pump. There is almost no pressure resulting from the pump actually at the big end. The pump gets it to the main bearing, from there it makes its way by centrifugal force. Even at 800rpm big end lubrication is marginal.
You must remember that this engine was designed to be started, warmed up in a very controlled way (1200rpm) and then run at max revs for the rest of the day. If allowed to idle at 500rpm it will destroy itself! There is no oil supply to either end of the slave con rods, they are lubricated only by splash. As there is quite a small angular movement in the joints between the master conrod and the slave conrods that is ok but they can not withstand the hammer action that results from huge play in the big end bearing. The damage you show was not caused by general wear, it was caused by idling at too low a speed.
Incidentaly the low compression ratio is effectively doubled by the action of the supercharger above about 1500rpm which is how it manages to make nearly 400hp.
You will have to completely dismantle the engine to make sure there is no swarf anywhere and to check / replace bearings that have been damaged.
Have fun, David
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22-01-14, 12:29
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