993 Longevity
10-03-2010, 12:07 PM
#31
Drifting
...the engine will have some wear...Quadcammer
...I interpret that to mean no wear putting it out of spec...dryadsdad
What I recall is that the dentist, a Californian, had a twice daily 100 mile driving cycle, from his home to his office, and apparently took good care of the car. It ultimately ended up in the hands of a California Porsche parts retailer, who bought it for a parts car. But the car was so good that he ended up restoring it and installing a special 3.5 motor that he had, and the dentist's engine ended up at a different shop.
That shop dismantled it, and cleaned and re-assembled it.
I've noticed that many of these high mileage vehicles have long regular driving cycles. Like Irv Gordon's famous 2.3 million mile Volvo P 1800; that guy loves taking long highway trips.
10-03-2010, 12:09 PM
#32
Team Owner
Thread Starter
If your question is "how common is a valve guide replacement for 993s", I think you might get a better answer from a shop that does a lot of air cooled cars. They would probably be able to give you an idea of how common it is from model to model, i.e. SC vs Carrera vs 993, etc, then you can judge for yourself if this is something to worry about.
As a matter of fact, contact a few shops to get the best picture. You could contact Peter Zimmerman. He is a renowned Porsche master mechanic, had been working on Porsches for over 30 years, up until he sold his shop. Do a search on the 911 board here.
A leak-down test should catch bad valve guides. The problem has to do with an inferior material, not with a poor craftsmanship on any of the porsche air cooled engines.
Other than valve guide issues and SAI clogged ports, there are no other common issues to give you reason to go into a 993 engine. The 993 engine is very robust. From what i've read, I would put the reliability of the 993 right up there with the SC.
As a matter of fact, contact a few shops to get the best picture. You could contact Peter Zimmerman. He is a renowned Porsche master mechanic, had been working on Porsches for over 30 years, up until he sold his shop. Do a search on the 911 board here.
A leak-down test should catch bad valve guides. The problem has to do with an inferior material, not with a poor craftsmanship on any of the porsche air cooled engines.
Other than valve guide issues and SAI clogged ports, there are no other common issues to give you reason to go into a 993 engine. The 993 engine is very robust. From what i've read, I would put the reliability of the 993 right up there with the SC.
Since mine is a 95, I don't think SAI clogs are an issue because if I understand these things, that won't affect the running of the car.
Our car passed the PPI just fine, but I don't see how it could have caught bad guides or seals. I don't think we have an issue because in about two thousand miles our oil usage has been trivial.
I"ve heard of Pete Zimmerman, but I don't think I'll bug him with a question until I have one with a bit more in it. Thanks.
10-03-2010, 12:16 PM
#33
Team Owner
Thread Starter
I inadvertently recycled this particular issue of Excellence, and I probably misquoted the article. The engine components would have had some wear, but been within spec.
What I recall is that the dentist, a Californian, had a twice daily 100 mile driving cycle, from his home to his office, and apparently took good care of the car. It ultimately ended up in the hands of a California Porsche parts retailer, who bought it for a parts car. But the car was so good that he ended up restoring it and installing a special 3.5 motor that he had, and the dentist's engine ended up at a different shop.
That shop dismantled it, cleaned and re-assembled it.
I've noticed that many of these high mileage vehicles have long regular driving cycles. Like Irv Gordon's famous 2.3 million mile Volvo P 1800; that guy loves taking long highway trips.
What I recall is that the dentist, a Californian, had a twice daily 100 mile driving cycle, from his home to his office, and apparently took good care of the car. It ultimately ended up in the hands of a California Porsche parts retailer, who bought it for a parts car. But the car was so good that he ended up restoring it and installing a special 3.5 motor that he had, and the dentist's engine ended up at a different shop.
That shop dismantled it, cleaned and re-assembled it.
I've noticed that many of these high mileage vehicles have long regular driving cycles. Like Irv Gordon's famous 2.3 million mile Volvo P 1800; that guy loves taking long highway trips.
I hung out at 'oil' sites for a while. The story there from the experts is that the engine wear occurs during start up. So a car driven regularly (so it keeps its oil in the needed areas between uses) will experience very little wear and almost none when driven reasonably. I suspect a good deal of the wear issues on 993 is from being garage queens more than anything else.
10-03-2010, 12:19 PM
#34
Drifting
Did your PPI include a cylinder leak down test? That is how bad guides are identified without intrusive work. Of course oil consumption is an even better indicator and if it is low you are ok. IIRC 1 quart per 600-800 miles = top end time.
10-03-2010, 12:22 PM
#35
Team Owner
Thread Starter
Yes, it did, but a leakdown test tests the leakdown in cylinders with both valves closed & engine at TDC. So it avoids the guides 100% or did I misunderstand what a leakdown test is?
10-03-2010, 12:24 PM
#36
Burning Brakes
The valve guides are above the combustion chamber, so if the valves are seated even if you had no valve guides at all the leakdown test wouldn't show it.
IMO...
Only way I can tell to measure valve guide wear is through oil consumption, or remove the valve covers, pressurize the combustion chamber and measure the valve stem side play.
EDIT, slow internet connection dryadsdad beat me to the question
10-03-2010, 12:48 PM
#37
Drifting
I suspect a good deal of the wear issues on 993 is from being garage queens more than anything else.
10-03-2010, 01:33 PM
#38
Burning Brakes
Just passed 102,000 miles. Burns oil at about 1 qrt per 2k. Runs exactly like it did the day I bought it with 30k..... I've owned a lot of cars but other then my Honda I have never own a car a rock solid reliable as this. I drive it 100 miles round trip to work 5 days a week and it shrugs it off like an econo-box. I even average 23 mpg! Pretty sweet for a 14 yr old sports car!!! Enjoy them and don't worry.
10-03-2010, 01:49 PM
#39
Race Director
I'll ask again, How does a leakdown test determine worn valve guides?
The valve guides are above the combustion chamber, so if the valves are seated even if you had no valve guides at all the leakdown test wouldn't show it.
IMO...
Only way I can tell to measure valve guide wear is through oil consumption, or remove the valve covers, pressurize the combustion chamber and measure the valve stem side play.
EDIT, slow internet connection dryadsdad beat me to the question
The valve guides are above the combustion chamber, so if the valves are seated even if you had no valve guides at all the leakdown test wouldn't show it.
IMO...
Only way I can tell to measure valve guide wear is through oil consumption, or remove the valve covers, pressurize the combustion chamber and measure the valve stem side play.
EDIT, slow internet connection dryadsdad beat me to the question
10-04-2010, 12:06 AM
#40
Pro
Hi
My car has done 185k and never smokes, taps or uses much oil. On the UK forums top end rebuilds that are actually needed are very rare. I will be doing one on my engine this winter, but for me it is part of the hobby and I am more concerned about general cleaning and replacement of rubber parts than I am about anything else. It will be interesting to see what I end up replacing while it is out.
All the best
Berni
My car has done 185k and never smokes, taps or uses much oil. On the UK forums top end rebuilds that are actually needed are very rare. I will be doing one on my engine this winter, but for me it is part of the hobby and I am more concerned about general cleaning and replacement of rubber parts than I am about anything else. It will be interesting to see what I end up replacing while it is out.
All the best
Berni
Last edited by berni29; 10-04-2010 at 12:07 AM. Reason: sp
10-04-2010, 12:40 AM
#41
Racer
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No that wasn't my question. Mine was a bit larger. If there is a pattern of failure in the 993 which decreases the median time before one needs to do a major engine overhaul. When I posed the question, I didn't know the top end jobs I'd read about occurring at what I consider very low miles (under 50k) were due to guides or something else.
Since mine is a 95, I don't think SAI clogs are an issue because if I understand these things, that won't affect the running of the car.
Our car passed the PPI just fine, but I don't see how it could have caught bad guides or seals. I don't think we have an issue because in about two thousand miles our oil usage has been trivial.
I"ve heard of Pete Zimmerman, but I don't think I'll bug him with a question until I have one with a bit more in it. Thanks.
Since mine is a 95, I don't think SAI clogs are an issue because if I understand these things, that won't affect the running of the car.
Our car passed the PPI just fine, but I don't see how it could have caught bad guides or seals. I don't think we have an issue because in about two thousand miles our oil usage has been trivial.
I"ve heard of Pete Zimmerman, but I don't think I'll bug him with a question until I have one with a bit more in it. Thanks.
To get very specific statistical data which you might use to predict failure, you have to have very comparable cases. But you have so many variables working against being able to compare one car to another. First there are manufacturing tolerances, then the way people drive their car, the way people take care of their car, the types of products (oil is a biggie) that they use to maintain their cars, etc, etc.
Do you know what the base line median time is for the 993 engine to require rebuild?
10-04-2010, 01:12 AM
#42
Rennlist Member
I had a '78 SC targa. I ended up selling it when I moved aboard a sailboat. It had over 140k miles and the engine wasn't ever opened. The only mod was the cam chain tensioner upgrade. I raced that car but not seriously, but still, I did have it on the track.
Anyway, it had no issues on the PPI upon sale aside from cosmetic things in interior just due to age and use.
I've read here that some people with 993's are doing major engine work at 50k miles - like a new top end. Is this common? My P-car concept is that these are pretty much bulletproof engines unless some defect like a stretched stud or the tensioner fails grenading the engine.
Of course the 993 engine is more powerful than my SC engine but with not much added cc's. Are these cars doing six figure miles w/o major overhauls or has reliability decreased with the newer models compared to my SC?
Anyway, it had no issues on the PPI upon sale aside from cosmetic things in interior just due to age and use.
I've read here that some people with 993's are doing major engine work at 50k miles - like a new top end. Is this common? My P-car concept is that these are pretty much bulletproof engines unless some defect like a stretched stud or the tensioner fails grenading the engine.
Of course the 993 engine is more powerful than my SC engine but with not much added cc's. Are these cars doing six figure miles w/o major overhauls or has reliability decreased with the newer models compared to my SC?
1) Start the car and drive
2) Stay under 3k until it reaches temp
3) Rev to 5-6k a few times during each drive
4) Change the oil regularly
5) Rinse and repeat
