How many miles is a 911 motor good for ?

[Bob's Flat-Six]

I was wondering what you guys that have opened up higher miles motors are finding ?
What do the bearings look like with 200 thousand miles on them for instance ?

As some of you know I have a Big Cummings diesel 855 cu. in. that I just recently had rod and main bearings replaced on.
The standard crankshaft has about 400K total miles and the bearings were at about 210K when they were replaces.
It was a good time to do them as they were starting to show copper on about half the bearings. I did them at 179K miles the first time and no copper was showing.
This motor get's a lot of idle time so that is also a factor, plus working in city traffic and dirty conditions. It is maintained with regular oil changes.

This is what led me to the 911 motor question.

[nhromyak]

I haven't actually seen the bearings, but Bruce Anderson and (I think) a few here on Pelican have seen 300K on well maintained SC engines.

Are you only asking about main bearings? Or the engines in general?

[Bob's Flat-Six]

I guess I'm more curious about how the bearings look on these higher mile motors once they come apart. And how the crankshaft holds up.
Just curious how they fair in general in all conditions.

I have a feeling there good for a lot more miles than most think.
I'll bet the crankshafts will go 500K miles maybe more ?

[Grady Clay]

Bob,

Very good question!

I think the answer lies in three areas:

First, these are not designed to be “last-forever” engines. The basic design is for high performance. That said some last far more than expected. I would not push the envelope of durability. I prefer regular “maintenance overhauls” to stay on top of the performance curve. That is why we own these cars in the first place.

The engines are highly subject to the kind of use. I have race engines that I do a “maintenance overhaul” on every 25 running hours. They see 8300 RPM every shift and unavoidably 9000 occasionally. A nice street 3.0 SC doesn’t see that kind of demands.

Maintenance is the extender of life for any engine – over-the-road diesel or 911. Change the oil too often. Never overheat the engine. Proper driving techniques – don’t over rev cold, get the engine fully up to temperature every time driven, on an air-cooled 911 keep the revs up, drive it every day, and use full performance regularly when appropriate.


Keep track of the performance. When something is wrong, fix it. Don’t let creeping degradation sap your 911 of what it was built for.

Best,
Grady