964 Turbo in LA 45K, $43K
04-23-2008, 10:10 AM
#17
Rennlist Member
I remember that from my 87 930, which had a nice healthy engine but lower compression across the board.
My understanding on any later aircooled 911 engine is the stock valve guides are more prone to wear, beginning with the 3.2 Carrera. The 3.3 turbo motor might have been different, since it pre-dated the 3.2 Carrera ... but I would assume the 3.6 would have had the newer guides and Viton seals.
The important thing to remember is it is more likely that the exhaust guides wear more quickly and that there are many, many examples of 3.2 and 3.6 normally aspirated motors that have gone on for more than 100k miles without requiring attention, while others begin drinking oil at a lower mileage.
In short, the 3.2 Carrera, 964, 993 (and perhaps the Turbos as well) may wear out their guides quicker than they would with the harder phosphorous bronze ones, but that doesn't mean *your* motor will have a problem, as long as the oil consumption is good and it runs well.
As a point of reference, my 3.6 993's guides were very worn at 60k miles. And, it's also important to note that the factory never considered it a "problem" -- mostly due to its own guideline that using a quart of oil every 600 miles or so is perfectly okay -- an amount that most owners would balk at. My 3.6, with fresh valve guides, uses no oil at all as far as I can tell. But my previous 993's wanted as much as a quart per 1000 miles, but still had great leakdown and ran perfectly.
My understanding on any later aircooled 911 engine is the stock valve guides are more prone to wear, beginning with the 3.2 Carrera. The 3.3 turbo motor might have been different, since it pre-dated the 3.2 Carrera ... but I would assume the 3.6 would have had the newer guides and Viton seals.
The important thing to remember is it is more likely that the exhaust guides wear more quickly and that there are many, many examples of 3.2 and 3.6 normally aspirated motors that have gone on for more than 100k miles without requiring attention, while others begin drinking oil at a lower mileage.
In short, the 3.2 Carrera, 964, 993 (and perhaps the Turbos as well) may wear out their guides quicker than they would with the harder phosphorous bronze ones, but that doesn't mean *your* motor will have a problem, as long as the oil consumption is good and it runs well.
As a point of reference, my 3.6 993's guides were very worn at 60k miles. And, it's also important to note that the factory never considered it a "problem" -- mostly due to its own guideline that using a quart of oil every 600 miles or so is perfectly okay -- an amount that most owners would balk at. My 3.6, with fresh valve guides, uses no oil at all as far as I can tell. But my previous 993's wanted as much as a quart per 1000 miles, but still had great leakdown and ran perfectly.
I spoke to my mechanic last night who does a lot of performance engine builds and he said he has seen some engines come in with worn valves but these engines are usually beaten hard. 100% track miles or poorly maintained. His comment was that it all depends on how the car was treated and it is something that afflicts all air cooled engines. Treated poorly, valve guide wear; treated properly and he says they last. Also if temperatures are allowed to soar on these engines it will create premature wear.
Also to add that the turbos run hotter and therefore rebuilds may be needed early because of the extra heat but this goes for the 3.3 as well as the 3.6 l single and TT motors. Although there are turbos out there with well over 100k miles and still running.
Edit: Interestingly as I read some of the comments on the 993 forum it would appear the 993 3.6 l seams to have a higher rate of VGW than the 964. the 993 uses a different valve guide than the 964.
04-23-2008, 11:19 AM
#18
Addict
Rennlist Member
Rennlist Member
I spoke to my mechanic last night who does a lot of performance engine builds and he said he has seen some engines come in with worn valves but these engines are usually beaten hard. 100% track miles or poorly maintained. His comment was that it all depends on how the car was treated and it is something that afflicts all air cooled engines. Treated poorly, valve guide wear; treated properly and he says they last. Also if temperatures are allowed to soar on these engines it will create premature wear.
I think the bottom line is how well your particular car runs and whether or not it's really drinking oil. My 97 runs much tighter and "better" now that I have had the top end done, as well as using no oil at all anymore, but it was really running quite well before, and I wouldn't have done it if not for the SAI system issues. But all in all, it was $3500 well spent.
My favorite quote from my favorite mechanic -- years back when I had a 911SC with a broken head stud that ran just fine irregardless -- is "Just drive it and quit worrying about it."
04-23-2008, 12:19 PM
#19
Rennlist Member
There are different schools of thought on this; some people believe oil consumption is related to the initial break-in of the engine, according to how well the rings seated (or didn't). Some of the early 993 engines had problems in that regard where the rings never seated. Others feel short trips on a cold engine causes the guides to wear. Some debate the role of the undertray. Others believe if you rev the heck out of it all the time it will wear less than if shift like your grandmother would. Who knows the truth?
I think the bottom line is how well your particular car runs and whether or not it's really drinking oil. My 97 runs much tighter and "better" now that I have had the top end done, as well as using no oil at all anymore, but it was really running quite well before, and I wouldn't have done it if not for the SAI system issues. But all in all, it was $3500 well spent.
My favorite quote from my favorite mechanic -- years back when I had a 911SC with a broken head stud that ran just fine irregardless -- is "Just drive it and quit worrying about it."
I think the bottom line is how well your particular car runs and whether or not it's really drinking oil. My 97 runs much tighter and "better" now that I have had the top end done, as well as using no oil at all anymore, but it was really running quite well before, and I wouldn't have done it if not for the SAI system issues. But all in all, it was $3500 well spent.
My favorite quote from my favorite mechanic -- years back when I had a 911SC with a broken head stud that ran just fine irregardless -- is "Just drive it and quit worrying about it."
I am not worried by any means. I know these cars well after nearly 30 years and fully understand the pros and cons. I just like to educate myself about them and even after 4.5 years on this forum I keep learning new things all the time.
04-23-2008, 02:06 PM
#20
Drifting
I agree, break-in is especially important. That topic itself is a whole can of worms. My first new motorcycle back in '78 I broke in gently and "by the book", it always used oil. Years later I learned you need to be mildly aggressive without abusing the motor, to get the rings seated. However, I thought Porsche broke in the motors before installation or are they just give a short bench test?
Anyway, from the 3.2 and on, each increase in HP of the air-cooled motors has brought higher heat output and increased valve-guide issues. The best solution for the 993s looks to be good aftermarket guides. With 93k currently on my car I'm sure I've got some wear but consumption is less than a quart in 2k so unless I develop an SAI problem I don't expect to have to touch the top-end for quite a while.
Anyway, from the 3.2 and on, each increase in HP of the air-cooled motors has brought higher heat output and increased valve-guide issues. The best solution for the 993s looks to be good aftermarket guides. With 93k currently on my car I'm sure I've got some wear but consumption is less than a quart in 2k so unless I develop an SAI problem I don't expect to have to touch the top-end for quite a while.
