1956- Case 311-B

On leaded vs unleaded gasoline djm75 is right. The lead was to protect the softer valve seats used in automobile engines. Most tractors were designed to run on kerosene or tractor fuel which did not have TetraEythl lead consequently they are hardened seats which is what Detroit had to do to car engines in the 70s.

THe only engines that should use non detergent oil are two cycle engines and it is a special oil for them as it get mixed in gas or injected directly into the combustion chamber as these engines have no crankcase and the oil in the gas lubricates the engine. Detergent oils help keep your engine clean.

If she really gave you TetraEthyl lead to put in the tank, take it to the nearest hazmat site and try to get it disposd of and out of your hands. This is one of the most toxic substances known to man in undiluted form. It was even bad in gasoline as it can be absorbed through the skin.

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

Pull the valve cover off, if the head does not have a layer of sludge you can probably get away with switching to detergent oil and frequent changes as John said. Don’t get too excited about the sludge you will probably find in the top of the valve cover, that is more an operational thing, make your decision to pull the pan or not based on the accumulation on top of the head.

Joe

Both have the 148 cid engine. The engines have a low compression ratio, something close to 7:1, you do not need leaded gas. Head is cast iron, valves are steel. No aluminum in the engine that I can think of off-hand except the rear main seal carrier.

Detergent oil is best for this engine since it keeps particulates in suspension but if it has used non-detergent oil for many years, there may be built up gunk in the crankcase & lube system that detergent oil will tend to put in suspension and cause problems. If you know the engine hasn't had frequent oil changes in the past it's best to drop the pan, check for gunk, clean out before switching to detergent oil.

Joe