I wouldn’t worry too much about it, though you might want to get the valves adjusted soon. I’d also check the compression and get the timing set. Tractor engines are low compression and run at low RPMs under relatively light loads. There just isn’t that much fuel getting burned in the cylinders, and the valves may be able to lose excess heat through the valve stems.
The exhaust valves in higher compression engines wear when the exhaust heat the valve face almost to the point of melting and then the valve is shut. The valve welds itself slightly to the exhaust seat, and the softened metal gets knocked off as the exhaust goes past. Retarded timing can aggrivate this, as the fuel may still be burning when the exhaust opens.
The valves in my parents’ '72 Dodge Dart slant six were mechanical. But they never clattered so probably never were adjusted. Years later when I bought my mother’s '78 Aspen slant six, I took it in to a dealership to get them adjusted and had to argue with the white lab coat writing the order that the valves weren’t hydraulic, then persuade him that the engine had to be cold.
Studebaker Lark sixes had mechanical valves, too. A '62 belonging to the parents of a friend clattered like mad, but they ignored it until any adjustment was useless. It scared the neighbours for a decade. I had the Aspen’s done because of that.
Adjusting the valves in my '82 four-cylinder Yamaha 500 was murder; it had 16 of them. But because of that Studey, I plugged away. Hours later I gave up, and because they had to be adjusted cold, I walked the thing to the bike shop a couple of miles away. It was good I didn’t ride it because I had made a couple or three too tight. I would have had the only Yamaha Lark in existence.
The inventor of hydraulic valves should have won a Nobel Prize.
FTR some engines are going away from hydraulic to solid lifters so that the ECM does not set missfire codes from the lifter pumping up slightly.
No question that hydraulics are easier, unless they fail. A lifetime adjustment beats the hell out of replacing lifters.
The idea goes back farther than that, though. Tucker had a similar idea for his 589 engine, using oil instead of air, however, he never had the time to get the kinks worked out of it. I suspect that the idea goes back even farther, but I don’t really know. One of the high end Japanese car makes has valves controlled by an electromagnetic solenoid, IIRC.
Interesting. I wonder what the great man’s plans were for timing actuation? Obviously, digital processing didn’t exist back then, so some form of analogue mechanism would have been needed. I wonder what his plans were? Theoretically, the idea still has lots of merit. I’d personally trust a hydraulic pneumatic system more than a compressed air system if it was bulletproof. Something nice and ultra reliable like the Bosch K-Jetronic system. That is, not the best in the world, but just wonderfully simple and reliable.
AFAIK the complete blueprints for the engine no longer exist, however, at least two of the engines survive and are in the hands of a Tucker owner. If I can ever scrape up the money, I’m going to try to sweet talk the guy into letting me take a peek at the thing, so I can do some CAD drawings of it. No idea of the mechanism, but I do know that they had problems with air getting in the lines and screwing up the valve timing (which is why they went with the 335 Franklin Engine).
I suspect you have cause and effect reversed: that slow-turning, torquey engines are usually designed with pushrods. That is, the main reason to have an overhead cam is to allow the engine to spin fast without valve float. Stump-puller truck engines and the like don’t need overhead cams because their engines are not tuned to develop power at high RPMs.
Now that makes sense. I can see pushrod engines being associated with high torque, but I don’t buy the notion that they have more torque because they have pushrods. I stand to be corrected if the facts are provided, but “common knowledge” does not a persuasive argument make. There are lots of widely believed misconceptions about automotive technology.