1947 Imperial and Chrysler Service Book – Cam Ground Piston

The secret is now out but long was not: Often the poor engine suffered that agonies of the damned. Why? Too much gas and water got into the oil, ruined the lubricating qualities of the oil, and made the engine wear out much faster. The worst situation was running the engine cold in cold weather. In particular there was that little device, the "choke": It's job was to flood in lots of excess gas hoping to get an explosive mixture from the cold air. Well, a lot of that gas didn't burn, got past the piston rings into the oil. Similarly for water from condensation.

The big step up was to have some exhaust flow under the intake manifold to heat the incoming fuel-air mixture to do better vaporizing the gas and need less extra gas from the choke.

What solved that was fuel injection, in various forms, throttle body, port, and cylinder. Then the pressure on the gas was high enough to get good vaporization.

Next biggie was spark timing: Usually it was far from where it should be again causing inefficient combustion and gas and water in the oil.

One of the most critical needs for lubrication was the rocker arms, e.g., where the rocker arm was pushed on by the push rod from the lifter on the camshaft. On a classic small block Chevy, I had a push rod go through rocker arm and the valve cover! We got a new, 'crate', engine via Chevy.

In the sense that why it is entirely true that cars (not only the engines, but also the clutch, and brakes) needed a lot more maintenance and much earlier repairs/replacements, the cost of them was relatively low.

The big advantage is that you can run now a car for thousands of km/miles without doing anything to it and - usually - it never stops/breaks. (but when/if it does, your wallet will notice it)

Besides the "almost continuous" oil changes and filter replacement, once upon a time it was "normal" if you were planning to make a - say - 500 km trip, to go a few days before to the mechanics and having him check the car, and anyway you rarely had a clutch go beyond 60,000 km (40,000 miles) or (drum) brakes go beyond 40,000 km (and registered/checked every 20,000 or so), and the same goes for minor components (that someone that only had "new" cars probably don't know they even exist) such as the steering rack, rod ends, wheel bearings, all of these were routinely replaced or fixed at a relatively low mileage, besides needing to be "constantly" greased manually.

But for example the water pump, that rarely lasted more than 40/50,000 km, was fixed by disassembling it, replacing the bearings and seals, with a cost of a few dollars.

Nowadays you replace it only maybe once in the life of the car, say around 100/120,000 km, and it is easily a 300-500 US$ job.

The only thing that I find has gone "for the worse" (though there are reasons for the change) is the timing belt.

Old engines had a timing chain instead that never broke in 120,000 km or more (in some rare cases it may have "jumped over" a tooth of the sprocket, going slightly out of sync) and even when it broke, the engine was built in such a way that the valves had no interference with the pistons, if the timing assembly broke the engine would simply stop working, and in any case you could "hear" that the timing chain was worn out by the typical "ticking".

New engines timing belts need (in some cases) to be changed much earlier, like 40,000 km or so, and the issue being that they break more easily and when they do they do it "suddenly", and since new engines are more compact and differently designed (for efficiency/low consumption), when a timing belt breaks it will inevitably bend some of the valves (if you are lucky) or break the engine head (if you are unlucky) in both cases you have before you a mechanic's bill of several hundreds or a few thousands dollars.

As well, a modern car very rarely leaves you in the middle of a trip (unlike old cars may have), but the difference is that in the old times in most cases any mechanic/pump station would have repaired it somehow with available pieces, whilst now - in the much more rare case of an issue - you typically need a replacement car because what has broken is a small piece (often electronics, like a sensor) that local spare parts warehouses (where they still exist) do not have in stock, and that needs to be ordered taking two working days to get delivered, and possibly the replacing needs to be carried on by an authorized dealer because a special software is needed to do the pairing with the new sensor.

Thanks very much for the follow up!