Factory v. Shop Engine Rebuilds

[Superman]

I was getting dizzy reading, and then glossing, and then just paging through the remarks about Harold's FrankenPorsche (Randy's last post should probably have been the last in that thread), and I have a question.

Jack said rebuilt engines do not have the longevity of factory-built engines. I respect Jack a great dea, we all do, and I have even heard other folks make this same assertion. But I'm not sure I buy it. In my humble yet legendary opinion, if all the surfaces are machined properly, and if new parts are used such as pistons, cylinders, etc., then I guess I'm asking why a factory built engine would have any advantage over a careful, skilled, perhaps professional rebuild.

FWIW, most of the folks I have heard make this assertion (Jack's assertion) also seem to believe that engines are at the end of their life when they approach 100k miles. I vigorously refute that.

So, whaddya think, dudes and dudettes? Can a shop rebuild be as good as a factory engine?

[RoninLB]

Originally posted by Superman

that engines are at the end of their life when they approach 100k miles. I vigorously refute that.

all conditions equal.. forged vs cast pistons..cast pistons cocky poo after 100k............Ron

[ChrisBennet]

I think that a factory built motor is going to have some longevity advantages. For one thing everything is new. I doubt the average rebuild uses new oil pump, crank, etc. Granted the factory made some mistakes (valve guides).
-Chris

[arrivederci]

I'm not sure I agree with Jack either. We all know that the factory hasn't always built their engines to last forever. Lots of engines are notorious for weaknesses that can be corrected.

If I recall correctly, the newest motors that had issues were 964 3.6s...most were repaired under factory warranty. All pre-'84 motors didn't have pressure fed tensioners, and the '74-'77 2.7s are notorious for issues (as delivered from the factory).

[Jack Olsen]

I should clarify a little. I was saying that, statistically, there are going to be a higher quantity of mess-ups from small-time rebuilders than from the factory -- viewed as a broad sample.

I think the best engine rebuilds are probably not going to come from the factory, but from skilled rebuilders. The problem, as Noah points out, is that there is no uniform method of quality control accross all the people doing engine rebuilds, where there is some form of it (albeit not a perfect one) at Porsche.

I wouldn't make any categorical statement about which rebuilds are good and which are bad. The problem, though, is that there isn't much incentive for most rebuilders to take all possible steps to ensure engine longevity (not many 10-year, all-inclusive, owner-transferable warranties on rebuilds). Porsche needs to have most of its engines do well over the period of the warranty, if only to reduce its costs.

Again, there are many rebuilders (like Andial) that I would say are extremely reliable. There are also lots of small mom-and-pop-style shops that I'm sure do top-notch work. But it's hard to say anything about the work of such a wide number of rebuilders that's going to be accurate, other than that there are likely to be a fair number of people who don't get it quite right.

If I rebuilt my own engine, and I knew that I had done it right, and I knew I had access to a comprehensive volume of engine rebuilding knowledge, then I'd see no reason to expect anything other than a very long lifespan from the motor, barring the failure of parts and components that I had no control over.

But if you asked me to guarantee the work of 10,000 other guys like me, I'd say I couldn't put too much of my own money into backing up their work.

The factory, on the other hand, has to do this (effectively) for all the motors it produces.

[Mike Kast]

That was a glorious clarification Jack. You can rebuild my engine anytime...

[billwagnon]

Sheriff Jack should consider a career in the wordsmithery industry.

[speeder]

When it comes to rebuilding Porsche engines, I trust myself. And maybe this guy:


Not sure about this guy:

[Matt Smith]

I vigorously refute that Randy's post should have been the last in the FrankenPorsche thread.
Lighten up Supe!

[Jack Olsen]

[pwd72s]

Ob la di, Ob la da. La, la la, la...life goes on.

[Wayne 962]

Wow, a perfect topic for me to pontificate on! Here goes:

Without a doubt, a good quality rebuild is *better* than a factory engine. Without question, the technologies used in the factory engines were often suspect. Early magnesium cases suffer from pulled studs. 1974-76 engines had bad valve guides. 911SC & Carrera engines have broken head stud problems. Later cars had rod bolt and valve guide problems. The list goes on...

By utilizing the collective knowledge of what has failed in the past, someone rebuildling their engine can "fix" all of these problems when they reassemble their engine. Assuming that they spec and use all new parts where necessary, and follow accepted and meticulous rebuild procedures (as documented in my new book), then there is no reason why a rebuilt engine can't last as long (or more probably longer) than an equivalent factory unit.

On the issue of reusing oil pumps, etc... Most reused parts have lives of hundreds of thousands of miles and have equivalent performance from rebuild to rebuild. I can't recall the last time someone said that they had to tear down and rebuild their engine because their oil pump had worn out.

-Wayne

[Superman]

Matt, please imagine me smiling every time you read one of my posts. I'm very very slow to anger, or even anxiety. It chews me up, so I just don't go there. I'm relaxed, trust me.

Jack, I hope I did not sound critical. In fact, some motorheads I trust still believe that (at least with V8 engines) processes like boring cylinders are more accurately done by the HUGE fixed machines at the factory, than the smaller, adjustable boring machines in rebuild shops. So, they believe the factory is capable of greater accuracy than local machine shops. Ergo, the question I posed. You had no backtracking to do, though I appreciate your clarification. And I agree with it and Wayne's post.

[dd74]

It seems that only when an engine "needs" a rebuild, can it be given the opportunity to exist as a better engine. Of course, this does rely on how competent the shop or person is who is doing the rebuild.

On the other hand, there are some Porsche engines which may "never" need a rebuild. Case in point: the SC engine. BA states in his book that certain modifications have never been tested on 3.0 engines because they were too reliable to take apart; i.e. such as a displacement modification as he describes on page 144-145 of the "Performance Handbook."

But in the case of the 2.7, certainly it can be made "better" by a rebuild. One issue I've heard about 2.7s even after good rebuilds, is that they will still suffer oil leakage in a few months' time.

So the 2.7 might be the (slight) wild card in the philosophy of a reliable shop rebuild being better than a factory build.