Rebuilds at low miles

[MichaelUD]

I don't get it.
If Porsche engines are bullet proof, why are the engines rebuilt at such low miles? I read the classified section here and read of cars with 65,??? Miles with a fresh rebuild! My 2005 diesel jeep Liberty has 93,000 and is going strong. No rebuild necessary. So what's the issue with the Porsche? By the way, I've got a 1976 911S with 49,200 original miles on the clock.

[patz]

Money shifts.

[fanaudical]

There's lots of potential reasons. Here's a sampling:

- Over-rev and blown motor.

- Poor maintenance, leading to premature component failure.

- Car/motor sat neglected for years without moving; somebody rebuilt just to be sure what's in there.

- 2.7 with thermal reactors, 5-blade fan, no external cooler, driven hard, and pulled head studs.

- Nice garage queen that only gets driven to/from the race track for the weekly DE...

These motors (especially the early ones) like to rev and subsequently get worn out a bit faster. I'm guessing that your Liberty doesn't hit redline every time it leaves the garage...

That said, there are lots of well-cared-for Porsches out there with high mileage motors.

[MichaelUD]

That explanation makes sense. I read of a 356 with a rebuild after only 65,000 miles. Either the engines are crap or there's another issue. Apparently it's the other issue that requires a low mileage rebuild.

True, my diesel jeep never reaches redline. Neither does my Porsche. So I hope the "bullet proof" engine lasts a good long time.

[wayne robson]

Use,-----here is a few examples, not using your A/C,guess what can happen,
----------Left when not used for longer than six months with dirty, old, acidity engine oil.
----------putting wear and stress on bores and rings inside .
----------clutch stuck to plate ,like in gear some times.
----------stored in cold damp areas, alloying corrosion into wiring,electrics, tires, suspension
----------and interiors .
----------Use your windscreen washers.
----------etc--etc--etc.
So you can keep your classic in good low miles condition, by at least driving it every month or so, to at least 50 to 100 miles, using most accessories and it will last
for thousands of mil;es and years.

[DanielDudley]

911s don't like to be started and warmed up in the driveway. You start your car, wait about 30 seconds, and start driving. Even so, they like to be warmed up before driving hard. Some model years had soft valve guides, and they can often start to wear at around 80K. Some model years have magnesium engine cases, and sometimes the studs pull out of the case, requiring threaded inserts. Porsche later replaced the standard steel head studs with so called dilivar studs, which were supposed to correct issues due to expansion. However, dilivar units often break with age. Also, you need to run an engine oil for flat tappet engines, one that contains ZDDP, an additive that was once common in engine oils, but is now no longer being used in oils for modern engines, because it is known to prematurely age catalytic converters. This causes problems with the cam and follower wear.

What you need to realize though, is that these are air and oil cooled engines, and are also all at least 30 years old at this point. And now you belong to a forum, where people come to get help with their mechanical problems, so you are going to be submersed in problems. It may start to look like all 911 have problems. Well, they do share common problems, and you will read about all of them here.

The fact is, once these problems are addressed, there is a very good chance that they will never resurface. In many ways, I'd rather run an engine with 100 thousand miles plus on it, that has had a top end job, and these issues corrected, than run an engine with 80K on it, because many of these engines will need some work before 125K. Even so, there are engines out there with 300,000 miles on them that are still running strong, and have never been opened up.

So why then are these engines considered bulletproof ? It is because IF you maintain them properly, and IF you warm them up properly, you can run them hard and long all day, every day, for years and years, and they just don't seem to wear out or break. Sure, they do have some known problems, and they sometimes need those problems corrected, but overall, they are tough engines that can be made to run very reliably.

Realize that these cars were always solid and tough, but were made at the time for an affluent clientele. While these are fairly simple cars by today's standards, the engines themselves have a lot of parts, and are fairly complicated and labor intensive to build or assemble. Even so, they are not so complicated that they are out of the reach of anyone with reasonable mechanical skills to own and maintain. Thus people can own and maintain what was once a premium sports car without paying expensive labor fees, IF they are so inclined.

Remember, these cars were originally designed and built for the 1964 model year, and in many ways all air cooled 911s share common characteristics with those original cars. Of course in many ways they also share a common heritage with the original Volkswagen Beetle, which was designed before WW2. Cars in those days were designed by a few individuals, not giant engineering teams with massive computers. Cars from that era are quirky, mechanically interesting, and all have very distinctive personalities.

The air cooled 911 was a remarkably durable and able car for its time, and it had a very long production run of 25 years. It was a tough car capable of being raced on Sunday and driven to work on Monday, something that you can still do with one. People drive them to the track, wash them and take them to car shows, and then go right back to daily driving them. Some of us are still doing that. But they are not modern cars, and never will be.

A good read on the 911 is ''The Used 911 Story'' by Peter Zimmerman. It is a really comprehensive look at the 911 in retrospect. Everyone should read this book before buying a 911, but it is a book that every new owner should read regardless. You will learn more in one afternoon that we can teach you here in a month.

[VFR750]

Perspective. In the 1960-1980s an engine with more than 60-65,000 miles was considered old. At the same time most Porsches were running past 100,000 miles

By the early 1990s electronic fuel injection was becoming common. And engine life expectancy climbed significantly. I think this improvement is under appreciated.

[deguitars]

I have often wondered the same thing and it's not just cars left in damp garages or whatnot. It is not uncommon to see an SC with 50-75K miles for sale describe as "well maintained with fresh engine and gearbox rebuild". That's not bulletproof by any stretch in my mind.

Sure cars have become more reliable in modern times but lots of older cars using the same vintage technology as the 911 were far more durable. I once had a '74 BMW 2002tii, now that was the definition of bulletproof. Vintage 911's have some general engineering shortcomings that no one likes to admit (as do most cars including newer 911s...can anyone say IMS bearings?) and it's always felt to me there's a little of the "shared Cool Aid" philosophy to the vintage 911 culture. Don't get me wrong, 911s are good cars but I don't see the point in perpetuating this idea they are "bulletproof".

[manbridge 74]

Nothing is bulletproof.

Another thing to remember is leaks. Getting the number eight bearing area sealed up is generally a split case proposition.

Many people can't maintain a pocket knife much less the conglomeration of hardware that is an automobile. So you'll find cars with worn out cylinders at 50k due to lack of oil change, low oil level, beating on engine when cold etc, while another car has original cross hatching marks visible at 150k due to fastidious maintenance and, most importantly, not letting temps get too high.

For the OP, I wouldn't fret your car too much. Mid-years frequently need valve guides replaced around 50K but improved guides are available. The 2.7 can last a long time and in Europe it doesn't have the stigma attached that we have here in the states.

And from a more anecdotal perspective, we recently tore down a virgin 75 with reactors and no front oil cooler. Around 140k and no pulled studs or other surprises. Getting valve guides, rings and reseal only. Not too shabby for 41 years old.

[pmax]

Originally Posted by deguitars

Vintage 911's have some general engineering shortcomings that no one likes to admit (as do most cars including newer 911s...can anyone say IMS bearings?) and it's always felt to me there's a little of the "shared Cool Aid" philosophy to the vintage 911 culture. Don't get me wrong, 911s are good cars but I don't see the point in perpetuating this idea they are "bulletproof".

I don't think any of the experts actually said they were "bulletproof".

If you read the classic 911 guide books by Anderson, Morgan etc, the flaws and possible issues with each model are laid out quite clearly, some worse than others. These are old cars, air cooled, high performance at that time and they do not share the benefits of modern engine management. All these factors allow modern vehicles to last longer between rebuilds (or disposal).

[930cabman]

Originally Posted by manbridge 74

Nothing is bulletproof.

Another thing to remember is leaks. Getting the number eight bearing area sealed up is generally a split case proposition.

Many people can't maintain a pocket knife much less the conglomeration of hardware that is an automobile. So you'll find cars with worn out cylinders at 50k due to lack of oil change, low oil level, beating on engine when cold etc, while another car has original cross hatching marks visible at 150k due to fastidious maintenance and, most importantly, not letting temps get too high.

For the OP, I wouldn't fret your car too much. Mid-years frequently need valve guides replaced around 50K but improved guides are available. The 2.7 can last a long time and in Europe it doesn't have the stigma attached that we have here in the states.

And from a more anecdotal perspective, we recently tore down a virgin 75 with reactors and no front oil cooler. Around 140k and no pulled studs or other surprises. Getting valve guides, rings and reseal only. Not too shabby for 41 years old.

+1 our 1975 911S is still rockin just fine, however I was told a prior owner changed the mill to a 3.0, ...

BTW these are high perf motors, I do not have the specs, but I would bet the power/liter is greater than most with our flat sixes

Rock on, be safe

[RDUNCe30]

Here is a single data point:

I bought my 82 SC from Peter Z. two years ago. I have put about 8000 miles on the car. I am just over 211,000 miles. Original 3.0 engine, matching numbers as per COA. Stock engine, stock exhaust, trombone oil cooler, no a/c. Entire life in California prior to my purchase.

Current mileage over the life of this car works out to 6,028 miles per year. From Peter's notes to me and the Carfax, it appears that the car was a DD at some point, so there were years early in the car's life when it was driven more than the 6,028 average. It didn't get many miles on it during Peter's ownership.

As far as Peter knew, the engine had never had any serious work done to it. Under his care, the car did get replacement camshafts (new o.e.); it was updated to Carrera oil-fed tensioners (new o.e. kit including lines, brackets, clamps); got a new airbox; engine oil thermostat was resealed and oil pressure sender for warning light was replaced all at 193,400 miles.

Peter was kind enough to provide me with advice on how to drive the car to enjoy and preserve it as well as what oil, etc. to use based on his experience. I use ethanol free high test, Valvoline Racing VR-1 20w/50 oil, Kendall 80w/90 GL-5 gear oil. I keep a large drip pan under the engine so it will be easy to see any leaks (very minor spotting after a week or more).

The engine pulls well, brief smoke at start up only if the car has been idle for more than a week. During really hot weather, I try to drive it at least once a week for 100 plus miles and get the revs up only after the engine temp is up.

My wife and I did about 150 miles yesterday in 85-95 F. Oil temp never got above 210, including some stop and go in Raleigh and driving briskly on country roads. The car keeps up just fine during a monthly get together and drive to lunch with various SCs and Carreras.

I expect the car will require work sooner rather than later, but I no longer have to travel for work and I am post knee surgery, so until the engine tells me otherwise, I expect my miles per month will go up as the temperature falls.

Sam