I agree in principle with your post but not entirely.Compression ratio, firing pressure, firing temperature, coolant temperature and the latent heat of evaporation of the fuel mixture are all relative. The 148 cid gas engine was designed with a compression ratio of 7.1:1, 148 - 153°F coolant T-stat, with no exh valve insert seats. The same engine with high altitude/propane head was 8.5:1, 177 - 182°F T-stat, had a steel alloy exh valve insert in part because of the higher firing pressures, combustion, and coolant temps but also due to lower latent heat of evaporation of the propane fuel as opposed to gas, kerosene, or the so called tractor fuel. How did they do localized hardening of the individual valve seats? Laser hardening did not come into general use until the early 80’s, as far as I know, when we started to getting laser hardened liner ports and valve seats (in lieu of inserts) in diesels. Lead was added to gas to reduce exhaust valve & seat wear, and to a much lesser extent retard burn rate, because more vehicle engines were being produced with compression ratios of 9:1 and higher to boost hp, and higher coolant temps for efficiency while the latent heat of the fuel mixture remained the same. What was the first change that car manufacturer’s did when the leaded gas bane was proposed? In mass produced engines, they didn’t install inserts and I don’t remember any localized hardening. They did lowered the comp ratio of engines in new vehicles and recommended higher octane for their now high compression engines that were just yesterday’s low/medium comp engines. Valve seat "pound out" is more related to improper seating, grind angle, guide wear, etc than any amount of lead "cushioning". I am not proposing that lead is not beneficial in long term valve wear but it will not correct the main issues of valve pound out or prevent it. The only gas specification I can find in the manuals is “Octane 90.7, minimum, (ASTM Research Method)”. I think today’s 89 w/modern additives is probably adequate, don’t know for sure. I don’t see any reference to leaded or unleaded gas in the manuals. Am I missing it? Anyone? Joe
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