Lou and I have hypothesized that since # 7 & 8 cylinders are sharing the Crank Pin Journal toward the rear, next to the fattest Bearing, #5, we think that shared Journal got Hot.
Evidenced by the finding that # 4 Cranks lower main Cap is worn down to the copper layer. None of the other four lower or upper Main areas are affected in that way, as a matter of fact they are good. The Rod Pin Journals show the most ware and rightfully so, from my studies. Since the Pistons on their Rods are both spinning and reciprocating at the same time, while the Crank only has to turn.
Another factor to be considered, in my case, is the fact that some Engine builder put the Pistons in backwards for race reasons, seems to be the consensus. This trick may get you extra HP, but at the expense of creating Piston slap and shortening the overall life of an Engine, but racers and Moon shiners don't care about these things.
A third thing to consider is that the Pontiac block could be cooled better, hence I added the two 421 and Pontiac mods to my Block and Heads and the result from that is an evenly cooled Block. We measured this with a Laser temp. gauge, at each corner of the motor.
Since the # 7 cylinder was suspect at first after we listened to the motor with a stethoscope. Later confirmed to be the cause of the noise that we heard. Finally, visually seeing the ware on the Crank Pin Journal, all those score lines are rough, deep and into the smooth surface. We believe that friction and heat at the # 7 & 8 Rods were caused by the Pistons going up and down, had a direct and adverse effect on the fourth Crank Journals lower Cap Bearing, worn to the copper layer.
Last edited by TRADERMIKE 2012; 02-03-2024 at 01:24 PM.
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