Worn valve guide - need help

[polizei]

Hello all,

I have finished the PPI, head stud check, leak down, and compression test on a 1987 911 Coupe. The Porsche mechanic (well renowned and specializing in air-cooled) said the car is spectacular, but it's going to need a valve guide job in the future.

The car smokes on startup "more than normal" and a little bit on idle. The compression and leak down tests came back overly positive, so the mechanic's conclusion is that a valve guide job EVENTUALLY needs to be done. The car burns 1 qt. of oil for every 700-800 miles.

Question #1: How much should I expect to spend on a valve guide job? I've talked to a couple of air-cooled Porsche mechanics, and they both indicated $5,000. I've got the money to do that, and I like the idea of having the peace of mind that the car is closer to 100% mechanically sound - especially after investing a good bit already into the car. Should I not be losing sleep over this yet? This leads to my 2nd question...

Question(s) #2: At what point do I perform the valve guide job? What indicators should I look for? Am I hurting the car by not doing it immediately? The car has 60,000 miles on it.

Thanks for all your help!
Andy

[Eagledriver]

The actual work on the heads will run about 900 dollars from a shop. That is assuming you don't need new valves. I did a valve job myself on a Carrera and spent 3000 dollars when all was said and done. This included some other fixes and tools. I think 5000 is a good ballpark figure for this to be done by a reputable shop.

You are close to needing to get it done. I think the magic number in Bruce Anderson's book is 1 quart per 500 miles. The danger of leaving it too long is you could break a valve due to lake of heat conduction through the guide. I would try to do it soon but at most 1 year/5000 miles. (my opinion)


I would try to get 2500 off the price from the seller and buy the car. It sounds like a great car and the value will be higher after the engine work.

-Andy

[polizei]

I negotiated the price down $3,000 specifically for this issue.

[slodave]

I was under the impression, that valve guides may need to be replaced around 90,000 miles. Maybe I am wrong and I know that there are exceptions. I do know, that my engine has a little over 226,000 miles and has never had the guides replaced. The last few years have seen some aggressive driving. 175# on the last comp test after a day at Willow Springs. As I said, there are exceptions.

The top end $$ you gave seems about right.

Dave

[eskimo]

You know.. I just did mine for probably less than 1200$ total. I can guarantee that the valve guide/job was 600$ from HBP racing here in Denver, and then I bought some gaskets, some tools and a few other things relating to getting back on the road.

But, in my case I was avoiding (like the plague) the 'while I'm in there' and I've also owned the car for the 10 years, so I really didn't have any suprises.

'While you're in there' will kill your budget quicker than hookers in vegas.

[antaircooled]

I would drive it for a while and see how it goes - give it some spirited driving. Maybe it needs a bit of right foot therapy! I had a similar PPI on a '74 with 3.0 Euro motor four years ago and it still uses oil and blows oil smoke on startup. But it has done 20K miles and lots of track miles. It comes down to how you feel it is going and is it getting worse, has it lost power?

Maybe I am a cheap SOB but I would rather do that sort of work after driving it for at least 5k miles, checking oil levels regularly etc. You also get to know your car that way - they are all different. I take my car to red every time I drive it!

[polizei]

It sounds to me like most of you are of the opinion that it's ok to wait and see how it goes. I'm comfortable with that, and I feel like there's strong enough support in this forum to justify that. I just want to reiterate one more question.

If I delay the valve guide job, what risks am I taking on? Eagledriver noted that "the danger of leaving it too long is you could break a valve due to lake of heat conduction through the guide". It sounds to me like religious monitoring of the oil level would keep this issue at bay. What are your thoughts?

[North Coast Cab]

Sounds reasonable. However, if I were going through that trouble I'd try and replace the rod bolts as they are the real weak link on that motor.

[sjf911]

I don't quite understand what you meant by your leak down numbers.

Worn valve guides will typically cause smoking on deceleration and idle while driving, not so much at start up. They typically won't affect compression or leak-down unless really bad.

The valve failure risk comes from loss of contact of the valve stem to the valve guide resulting in lack of heat transfer, I don't think frequent oil changes are going to help there. There is a good chance that one or more valve stems will be worn out of tolerance as well and need replacement (not that costly).

Once you suspect valve guide wear, I would not delay as your risk of catastrophic failure is rising. I would also recommend replacing any worn valves even if still within tolerance (I would personally replace them all).

[notfarnow]

I read a lot of threads about 3.2 valve guide issues when I was making PPI arrangements on my dad's 86 carrera cab.

One thread had a few posts from John Walker, where he describes what happens if you let them go too far. The valves gets loose enough in their guides that they don't sit squarely in the valve seats. Left long enough, they'll beat the valve seats oval.

You may want to do a search on some of John Walker's posts

If your compression and leakdown #s were good, then the valves are obviously seating well. Just a consideration if you let it go for a while.

[yelcab1]

1 qrt per 700 miles is good.
$5000 valve job is fair for a good mechanic.
$1000 valve job is possible if you have all the tools and do it yourself, in-out and do not touch anything else.
Can you wait? I would wait and drive it until it absolutely needs it.

[polizei]

Originally posted by sjf911
I don't quite understand what you meant by your leak down numbers.

Worn valve guides will typically cause smoking on deceleration and idle while driving, not so much at start up. They typically won't affect compression or leak-down unless really bad.

The valve failure risk comes from loss of contact of the valve stem to the valve guide resulting in lack of heat transfer, I don't think frequent oil changes are going to help there. There is a good chance that one or more valve stems will be worn out of tolerance as well and need replacement (not that costly).

Once you suspect valve guide wear, I would not delay as your risk of catastrophic failure is rising. I would also recommend replacing any worn valves even if still within tolerance (I would personally replace them all).

Steve,
I'm new to all of this, and I'm still trying to get it straight in my head. Ultimately, the mechanic did in fact say that the leak down numbers were very good. One cylinder had a 6% leak and the rest were in the 1-3% range. His conclusion, in spite of the results of the leak down test, was that the valve guides EVENTUALLY need to be replaced. He said he concluded this based on the car smoking on idle and more than normal on startup. He also had the valve covers off and was able to inspect it.

I'm not mechanically minded so I don't espouse that I understand his conclusion thoroughly, but I do trust his judgment as his reputation goes before him. Is there a particular question I could ask him to better gauge how long I have before I should replace the valve guides? It seems to me that if a poor leak down test is an indication that the valve guides need to be replaced, and since my leak down test came back very good that I should be OK for a bit. Please correct and critique me if I am wrong in such thinking.

[sjf911]

The leak-down can be normal with worn guides. The best way to check is to have someone follow you while you drive the car and see how much smoking occurs when you decelerate to a stop and then idle. Worn guides will typically smoke heavily (can be quite embarrassing) while stopped but clear under acceleration.

Unfortunately, I don't know of any accurate way to check for wear without disassembly of the heads. I suppose if the smoking is light and you don't have an indication that one cylinder is burning oil more than the rest then watchful waiting may be in order especially if mild driving is the norm. I have a low threshold myself but I have been the victim of a "dropped" valve before.

[Zeke]

Like slodave, I have a lot of miles (235K) on an unopened motor that needs some work soon. Yes, it seems the motors will go on and on, but at what price? I may have some expensive head work in front of me. I just went through 14 (yes, that's fourteen) heads to find 6 good enough to rebuild for a 2.4. I had to satisfy a contract I made to supply some heads. Needless to say, I lost a lot of money.

[Joe Bob]

Try going with a heavier single grade oil......

[Zeke]

Originally posted by mikez
Try going with a heavier single grade oil......

Might not help those seats that are oval. At least in the long run. Lets; face it, you can run these things in to the ground and they'll keep on ticking...

(if you don't miss the big shift)

[ChrisBennet]

Of course it depends on your budget, but if a friend of mine had this problem I'd tell him to run it - until this winter and then I'd help him do the top end.

My philosophy with a lot of these things is that if they will need to be replaced during my ownership of the car, why wait until the last moment - so I can give the next owner the benefit of almost new motor/starter/alternator/shocks etc?

-Chris