Re: 50-hour engine test

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Posted by Matt Wilson [] on Wednesday, March 06, 2019 at 02:07:13 :

In Reply to: Re: 50-hour engine test posted by Vaughn [] on Tuesday, March 05, 2019 at 23:59:57 :

Thanks, Vaughn. I'm sure such testing is a standard and has been for decades, but I'm curious to know specifics of how it was done on our flatheads. Part of my curiosity stems from the seeming high rpm that they were reported to be subject to (according to forum posts), when many of us have the impression that these engines will come apart at such high speeds. I've read posts by people saying that they were subject to continuous 3600 rpm during these tests, and some folks say there is evidence that they also had to go through some period of testing at 4200 rpm, all of this reported to be at wide open throttle, with a requirement to show no significant wear at the end of the test (and of course, not fly apart either). This would seem to imply that maybe these engines are not as delicate under higher rpm operation as we might think. Don't get me wrong, I have no intention of operating my engine at anywhere near these rpms, but it just sort of fascinates me that these engines might actually do better than we think under such conditions.

Talking with flathead guru George Asche a couple of times, he tells a story of driving a 251 or 265-powered car on a nine-hour trip at engine speeds between 4000 - 4500 rpm the entire time. Why anyone would do that, I don't know, other than he's a known for being a speed demon. This was back in the early '50s. I asked him specifically if the crank, rods, pistons, rod bolts, etc. were stock and he says they were. I think he had power mods to boost the output of the engine, but otherwise stock. He also says the engine didn't seem to suffer any ill effects from this, either at that time or later. He also talks of racing at speeds up to 5500 rpm and knows others who took their Dodge/Chrysler flathead engines beyond that, again, with stock bottom end. He said once you go above about 6000 rpm, you have to start making oiling system mods but the crank, rods, and other bottom end part are stock. I believe virtually all his driving for the past 70 years has been behind the wheel of flathead-powered vehicles, mainly a one or two vehicles in particular, and I'm told he doesn't spare the rpms.

The engines in our Power Wagons and M37s had governors set to 3200 rpm, which I generally take to mean they were authorized to operate there continuously. Certainly a great many drivers would take it that way, especially as there seems to be nothing specifically prohibiting this in the manuals. I have no desire to operate my engine at this high of a speed, especially continuously, as I'm not much of a risk-taker, but it makes me question if the limits are really as low as people seem to think.

Anyway, this just interests me. As a mechanical engineer, who enjoys engineering history, I enjoy learning about the capabilities of our machines and delving into these questions, even if I have no interest in taking mine to such extremes.

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