Quote:
Originally Posted by Tony Wheeler
Of course, the effect of this 1 in 70 chance is that all four weak pots fire consecutively, followed by all four strong pots, followed by all four weak pots, etc. In terms of crankshaft acceleration / deceleration it's the worst possible combination.
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Good point! Further evidence of the massive moment of inertia of the rotating assemblies in these older engines which allows acceptable running even with such large differences between cylinders. I came across a Ferret last year that had the ignition timing set 90 degrees BTDC. Yet it started and ran. The only way I figured that could happen is the rotating assembly was damn near unstoppable once it got moving so it just drove through the period when combustion was trying to reverse its direction.
I wondered if this engine had ran very rich in its past, choke stuck closed-type rich, with liquid fuel trickling along the floors of the dual plane intake manifold and preferentially dropping down into the first holes it came to, the cylinders nearest the carb. But I suspect the gas wash would still have affected the corner cylinders to some extent, and my wet/dry compression testing didn't support bore/ring wear, so that scenario seems unlikely.