GregP
Major
Stock, I don't know how they compare. In practice, NOBODY builds one to stock specs today. Almost everyone in the business uses late-parts for any Allison that will actually fly, and the early parts and possible serviceable-but-unairworthy parts for boat or tractor engines. So ANY allison flying will likely have 90 - 100 series parts in it and will run pretty well.
Most flying Allisons have 12-counterweight crankshafts, intakes with turbulators in them, late valve lifters, and late wrist pins. All that come from Joe Yancey are balanced much better than stock from the original factory. I'd bet Vintage V-12s also builds a good Allison and balances it better than stock, too. Not too sure about anyone else. There was good shop in Washington state, but he retired ... doesn't have the specialty tools anymore. Got have the knowledge AND the specialty tools to get it done.
The old carb-overhaul guys also mostly retired, and their children mostly don't know how to overhaul a WWII carb. So, we're looking at a time when flyable WWII airplanes may start to taper off some from current levels of participation, largely due to losing the expertise in continuing to maintain and overhaul the flyable aircraft.
Most flying Allisons have 12-counterweight crankshafts, intakes with turbulators in them, late valve lifters, and late wrist pins. All that come from Joe Yancey are balanced much better than stock from the original factory. I'd bet Vintage V-12s also builds a good Allison and balances it better than stock, too. Not too sure about anyone else. There was good shop in Washington state, but he retired ... doesn't have the specialty tools anymore. Got have the knowledge AND the specialty tools to get it done.
The old carb-overhaul guys also mostly retired, and their children mostly don't know how to overhaul a WWII carb. So, we're looking at a time when flyable WWII airplanes may start to taper off some from current levels of participation, largely due to losing the expertise in continuing to maintain and overhaul the flyable aircraft.