At what mileage are you "guaranteed" to need a top end rebuild ?

[sugarwood]

I saw a post regarding a 138k mile car for sale.

One poster said "guaranteed top end rebuild"
How true is this?

If such a notion even exists, at what mileage are you "guaranteed" to need a top end rebuild ?

[bbturbo]

From what I have gathered over the years, there isn't necessarily a mileage tied to it. However, a leak down test will tell all. Some people will insist that it will need a top end soon at a certain mileage, but it is all based upon the leak down test and compression. Also, there are other variables such as: burning oil, broken studs, etc. that may encourage one done. Others more qualified will chime in soon enough with a better answer.

[faapgar]

When a motor needs to be rebuilt or freshened is dependent on the owners driving habits.A lot of people can not wait to get the oil temp up to 180 before they jump on the throttle.I used to live in a colder climate and # 3 rod bearing would fail first on some customer cars due to oil not up to temp.You can not compress a liquid so cold oil wipes the bearing.Good owners long life motors.

[Fixer]

Looks like the post was re 3.2 L Carrera. These cars (some) had premature valve guide wear. Mine ('86) did not and was fine at 165,000 miles still. It would puff a little oil smoke on start up if it sat a while like after Winter hibernation but that's all.
There's no definitive answer really so have PPI done.

[Jcslocum]

Just a very rough estimation would be 100K miles. Most folks that are in that mileage range that I know and had oil consumption from bad guides were at about that mileage, including my own 3.2. Compression and leak-down will not necessarily give an indication of worn guides. Only driving will tell by the oil usage. More than 1qt per 1000 miles of oil loss is when this get to be real and needs to be done.

[yelcab1]

There is no guarantee in life.

[Jack Stands]

My '87 cabriolet needed valve guides at 90,000, however my current '84 Targa is going strong with ne smoking and great leak down numbers at 134,000. I'd agree that it varies and you just have to maintain each car individually as needed.

[dicklague]

My 2.7 MFI 1973 is going on 150,000 miles with no problems. I am very religious about oil changes and warming it up carefully.

the engine was built by Mark Kinninger of Black Forest in San Diego on 7R cases, so I am sure it is very solid.

[RSBob]

500,000 miles. No debate about driving habits, oil types or changes. Period.

[darrin]

When my '86 targa needed a top end rebuild at 80k miles, I recall reading that carreras were especially susceptible due to Porsche's use of "improved" valve guide seals on the 3.2 motors that lead to oil starvation issues in the valve guides (especially on cars used for short trips that didn't fully warm up -- which was the case with my '86 targa daily driver). My mechanic used the older valve guides used on the 3.0l sc engines. I'm now at 180k miles and my oil consumption remains at well OVER 1.5k per quart. Granted, I now have a 20+ minute commute that allows my engine to reach and run at full operating temp consistently.

[Charles Freeborn]

No set figure. It's all about history.
Age sets in too as seals harden and shrink, so wear isn't the only factor. There are many components to when it's time.

[DanielDudley]

It's good if you get a car that has been done, because for many, it will be the last guide job the car will need, or at least until well past 200,000 miles. But, it is not unusual for a car to have a top end rebuild by 130,000 miles. One of the good things about having this done is that usually the new guides are of a very good quality, but also, this can mean that there is less worry about the dreaded cam lobe wear that was occurring more commonly a few years ago when oil manufacturers took the ZDDP out of conventional motor oil. This is often a reason to do a top end rebuild these days, and while you are in there, of course the valves will be ground and the guides replaced.

FWIW, I think that ''guaranteed top end rebuild'' would imply that the owner was promising that it had been done. Some of the best running 911 engines have over 130,000 miles on them and a top end rebuild. Many , if not most 911 engines see well over 200,000 miles on the original bottom end, and will just keep going and going with regular valve adjustments and routine maintenance. Use the correct oil, warm up the engine, and it will last and last.

Go over to the Rennlist forums and see if they still have a sticky on ''The Pre Purchase Inspection''. Or buy Peter Zimmermann's book, ''The Used 911 Story''. Well worth the read.

[chrisbruck]

My '87 was burning lots of oil at 144K. Had enough and at 163k did the top end.

[porschenut]

It needs it when it needs it, and not before. Mileage is not a deciding factor. Engine health is.

[Elombard]

Another way to ask the question:

Assuming regular oil changes with quality oil and a conscientious owner.

How many times can that valve go up and down against that guide before the clearance is too large and you start using a lot of oil.

I wonder what the answer would be?

I would guess that by 150,000 miles even a carefully operated motor could probably benefit new guides.

I guess the answer is you never really know unless you have owned the car since new.

If you have a 3.2 between 100 and 150K miles might not be a bad idea to imagine that a top end is in the future and plan for it, although its not necessarily urgent.

[Koizumi]

I did a rebuild at 118k because of 2 busted studs... The proverbial, well dang might as well do it all at this point... Kicked in. Even installed Supertec headstuds. Glad I did! I'm at 146k now, and the car runs great (aside from being crushed on one side by a 17' truck 2 weeks ago). Car will re-emerge from the body shop. Luckily the beautifully running engine etc are all intact!



You can only imagine the amount of damage. Some details are simply best to not show... They can be, frankly, really dang horrible to see!!!

[bemmett]

My '87 has 222500 miles on it without a rebuild. It burns, on average, a quart every 700 miles so it's probably getting close to needing one, but based on other threads here (and user manual) it doesn't seem like its in desperate need. But, it still pulls strong and doesn't smoke, so I'm going to see if I can make it to 230K and reassess when to get it done.

[autobonrun]

Guaranteed top end rebuild is:

1) 3 months after purchase regardless of mileage
2) 100 miles after you turn down the extended warranty

Whichever comes first.

I'm joking of course. There is no guaranteed mileage for a rebuild.
The statement itself is ridiculous. If any such magic figure existed, you'd see the sales price drop by the amount of the rebuild just prior to that magic number.

I've owned my SC for 33 years and have nearly 215k miles. It doesn't burn oil and still pulls strongly and has not had a top end rebuild. I routinely see SCs with 250k+ miles that have never had a top end rebuild. Now, can any car with over 100k miles benefit from a rebuild; I would say most likely yes. But benefiting from a rebuild and requiring a rebuild are two totally different things.

I would not be afraid of a 138k mile SC if it came with complete maintenance records.

[Ian Comerford]

I'm with him on this one^^^, no such thing as an average mileage

Ian

[florio]

So here is a related (opposite) question: I tore my engine appart and found a small ring ridge from where the piston ring had worn out the cylinder. It was maybe 0.1 mm judging from the wear on the cylinder compared to specs. These are biral cylinders from a 2.4.

Anybody care to guess the milage? I'm guessing some 100k, but I'd welcome a more experienced guess

dario