How long on worn valve guides?

[Doug&Julie]

Just a general question (perhaps a stupid one)...and I'm going to guess it depends on the car, but...how long will a 3.2 motor go on worn valve guides? I'm kinda curious because I've seen a number of high mileage cars for sale pretty cheap and I'm guessing it's because they're starting to wear their valves and use oil. (..or not, but for the sake of argument...and this thread..) So I'm wondering if I were to purchase such a car, how long will I be able to drive it before the valves HAVE to be done? Could it go for a couple of years? ...or is that too damaging to the car to risk?

Worn valves are the start of...what? Even further worn valves? Do they become loose and lose all compression? Do they damage the motor in any way if left for some time? I guess I hear so many people warn of warn valves/guides, but I'm not 100% sure how that is detrimental to the motor? (..or to what extent?)

Thanks for helping to cure my ignorance...

[88'3xBlk911Cab]

I am very curious about this question also as my 88' cab has 177K miles on it without any major work.......she only uses 1 qt of oil per 1K miles and smokes on start up after sitting for a couple of days but runs smooth and strong. We know the valve guides will have to be done but hope it isn't anytime really soon......

[CarreraS2]

My understanding is that valves use oil for cooling, and when the guides are worn the heat transfer out of the valve, through the guide, and outward from there isn't as good.

Of course, an overheated valve can lead to all sorts of problems, namely the valve breaking apart and falling into the combustion chamber of a running engine, wreaking all sorts of havoc.

[echrisconnor]

There will probably be many more definitive answers, but here's my take. There's a bunch of variables that will affect this. If the guides are just a little worn, as described in Blk911cab's thread, you may be OK for a couple years, depending on how much you drive it. Oil consumption and smoking are the telltales. If you get a car with really bad guides that smokes terribly and consumes a lot of oil, don't plan on driving it long.

The downsides of driving a car with worn valves follow:

1. embarrasing smoke
2. You will likely wear your vavles, so when replacement time comes you're looking at new valves in addition to head work.
3. In really extreme cases, you can drop a valve and cause catastrophic engine failure. The valves use the guides to dissapate heat and when worn, can overheat and shear.
4. You can beat up the valve seats a bit
5. Difficult to keep valves adjusted
6. a bunch of other things that I don't know...

[kepperly]

the problem with valve guide clearance is that if they are too loose they leak oil into the combustion chamber and the oil burns and deposits carbon on the plugs which eventually foul and the motor starts to run like crap.
It has been suggested that the factory installed too efficent
valve guide seals in the Carrera and the stems didn't recieve
ENOUGH lubrication. The clearance is critical in the Porsche motor
because this is also where the valve sheds heat, through the valve guide into the head. The result of the valve stem not being tight enough is that the valve over heats and the tulip end breaks off. Now you have large trouble. Mileage is all over the place on these motors requiring valve stems but when you do it,
make sure you pick someone VERY, VERY knowledgeable in Porsche heads. just my .02 for what it's worth.

Keith Epperly
87 slant nose turbo look carrera cabriolet

[Doug&Julie]

This all makes sense, thanks so much! (still welcoming other comments )

[Rot 911]

If you are using more than a quart every 500 miles you really need to address the valve guide issue. I waited until I was at a quart every 300 miles and barely averted disaster. As it was I ended up needing all new guides and valves. Look at this picture and tell me I wasn't living on borrowed time:

[88'3xBlk911Cab]

Ouch! I will definetly be keeping a really close eye on my cars oil consumption. I only plan on putting about 3-4K a year on her so I hope to nurse this for a while......but we will do the right thing when she starts getting tired.

[JeremyD]

I've heard from my wrench - that 400 miles per qt is about the very maximum you want to take the valve guide problem if you can live with the slight smoke at start up or anytime you down shift and create a vacuum in the combustion chamber(s). If you start fouling plugs before then- 400 miles/qt- (and some folks just have 1 or two guides that only leak). then you need to address it sooner.

[don911]

Just for reference. I bought my 87 with 173K on the OD and the engine had never been touched. I drove it daily and tracked it for 3 1/2 years. Oil consumption stayed about the same, 600-700 per qt. At the track I noticed higher oil consumption but I also developed an oil leak somewhere so alot of oil was going out the bottom. I replaced the motor at 210K only because a good 75K 3.2 came up for sale on this board for a fair price. My original motor was still running strong but with the oil leak and the mileage, it was time to start "thinking" about rebuilding. Rebuilds are spendy and a 210K motor I think would need more than new valves and guides so I just swapped it out. When I factor in the sale of my original motor, I swapped it out for less than the cost of just a top end rebuild.

One shop told me that until oil consuption hits 200-300/qt or plugs start to foul, to keep driving it. 400-500/qt is probably safer. In my opinion, high mileage 3.2s are the best deals out there if you find one that's had regular maintenance and just has high freeway miles.

[88'3xBlk911Cab]

Thanks for all the great advice and thank you Doug for starting this thread. I learn more and more about my car everyday from you guys.

[Doug&Julie]

Is this your first Pcar? I would have killed for a board like this when I bought my first Pcar. ...or my second. ...even my third. But we grow and we learn. I love this community.

[Bill Verburg]

Not only do you lose oil(very sightly) but the transfer of heat from the valve is hindered by the poor physical contact, causing the valve and consequently the engine to run hotter. Pinging can be an expected byproduct. This of course can lead to a miultitude of other issues.

It's not a go no go issue, the engine just runs poorer and poorer and uses more and more oil.

[88'3xBlk911Cab]

Thanks for the additional tips Bill. I am very keen to how my cars run having grown up with a master mechanic father. His road trip fun was "honey, what is that noise and what do you think is going wrong with the car". Made me a very keen observer and I pay close attention to all unusual sounds.

Doug, yes this is my very first P-car! Have always lusted after the 911's and finally made the dream a reality in May 2004. The timeless styling and raw creature comforts just appeal to me After my husband and I decided to turn our Cobra replica into a full time race car I really missed the feel of the open convertible. We put over 30K miles on the Cobra between long road trips and racing. I would freak people out by driving it to the grocery store! Loved the reactions I would get when the courtesy clerk would carry out my gorceries and I would say "oh, it is just over here....the blue one with the white stripes." Loved to see their mouth drop to the pavement.

I am not the average "woman driver". I grew up racing dirt bikes and had a 70's muscle car for almost 15 years. I help my husband work on our cars, I race autox and love doing DE's. I am no longer a "lady" once the helmet goes on

I am very happy to have found Pelican. I know I am in the minority being a lady on a mostly mans board but I read most all posts and learn about my air cooled wonder.

Happy New Year everyone!

Mary

[Doug&Julie]

Very cool Mary! I'd add a "welcome to the community" but you have more posts than I do!

[88'3xBlk911Cab]

Not many!

[aj88cab]

OK, just to complicate things, I just looked at the exploded diagram of the valve and guide assembly in the parts catalogue CD I just purchased from our host (buy it if you haven't). There are the following items:

Valve (with stem of course)
Valve guide
Valve stem seal
Sleeve for valve stem seal

Is it possible that some of our oil consumption problems are a result of worn seals and not the actual valve guides. And if so, can these seals be replaced in the car and/or without removing the engine/heads.

I am at about 600mi/qt with my '88 (118k miles). I stopped the startup smoking by letting it idle until the oil level guage stabilizes (about 5-10 sec) before I shut it off.

Happy New Years
Andrew

[echrisconnor]

Unlikely the seal alone would make much difference. And, to replace it, you'd probably need to pull the heads off. At that point, you're better off fixing the actual problem and replacing the guides.

[Rot 911]

On the Carreras the prevailing theory is that the stem seals did too good of a job and actually starved the valve guide of oil leading to excessive guide wear. So replacing the stem seals would probably not solve the problem.

[aj88cab]

Oh well, for a second I thought I could spend my (non-existant)valve guide fund on those track wheels and tires.

On the other hand Santa left me a compression tester and a leak-down test kit. Sounds like its time to see just how bad (or good)things are.

Andrew