Picture of Lifters, Flat, DLC, Roller

[N201MKTurbo]

1 hour ago, 201Steve said:

@PT20J I’m not old enough to have seen it in the field, but didn’t autos with flat tappets suffer after the oils started reducing zinc levels in their products? 60’s maybe?

I sort of restored a 1951 M38 Jeep last year. It had been sitting in a construction lot for about 20 years. The engine in it was designed in 1923. The cam and lifters looked brand new.

OK full disclosure, the engine was rebuilt in 1968...

Edited January 30, 2021 by N201MKTurbo

[EricJ]

1 hour ago, 201Steve said:

@PT20J I’m not old enough to have seen it in the field, but didn’t autos with flat tappets suffer after the oils started reducing zinc levels in their products? 60’s maybe?

Yes, ZDDP levels were reduced because the zinc and phosphorous was not playing well with catalytic converters.   It mostly affected hotrodders with flat-tappets and there was a lot of cam wear in some cases.  There are ZDDP additives that can replace it for cases when needed, kinda the equivalent of camguard, but for running rather than storage.

I used to race a Yamaha-designed, Ford-built V6 that had overhead cams with bucket-and-shim lifters, essentially the equivalent of flat tappets.   The ZDDP issue was a Big Deal for a while, but seemed to not wind up being nearly as much problem in a practical sense as people thought.  

[MBDiagMan]

On 1/29/2021 at 5:20 AM, larrynimmo said:

When we speak about automotive engines, typically they run under 2,000 rpm with less than 12% of the available horsepower....with a very clean lead free gasoline preserving good oil lubricating properties.  Aviation engines typically cruise 2300-2600 rpms at 55%-75% power adding operating stresses in addition to running oil that has been degraded by lead pollution.   Added to that our planes can sit unused for months unlike most cars.

according to my AI, most flight school engines (with 100 hr inspections and oil changes) go TBO without engine issues....fly often and many hours a year should help to get 2,000 hrs from an engine.   I have read that Lycomming has said that engines running on unleaded gas will be rated for 3,000 hr TBO.

Automobile engines have positive crankcase ventilation that does a massively better job of keeping moisture out of the crankcase.  Before that, in the sixties, engines slugged and corroded so badly I don’t know how they ran as long as they did.

[PT20J]

2 hours ago, MBDiagMan said:

Automobile engines have positive crankcase ventilation that does a massively better job of keeping moisture out of the crankcase.  Before that, in the sixties, engines slugged and corroded so badly I don’t know how they ran as long as they did.

Auto engines spend a most of their time running at part throttle where there is vacuum in the intake manifold. I don't know, but I wonder how effective PCV would be running at high MAP. Seems like the lack of sludge formation in our engines argues that the ventilation is sufficient.

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