Best valve guide alloy?

I have a '87 Carrera and it sometimes smokes(blue oil smoke) for about a minute or two after start-up, usually after sitting for a few days or more. This started about 5,000 mi. ago ; it has 112,000mi on the orig. motor. My question is, should the problem be worn guides what is the ultimate alloy for replacement? One parts supplier advertises Beryllium Copper as the best for both valve guides and seats. Others say a Silica-Manganese Phosphate is best for guides and stock seats are OK. From what I've heard the factory Phosphor-Bronze guides are problematic; too soft and can't take the heat. Looking for longevity on daily driver here, what's best? Maybe oil is just seeping past the rings during long periods of sitting? Seems possible due to oil reservoir being higher than engine sump. One thing more, a brown deposit has always accumulated on the bumper near the exhaust; oil(Mobil 1)consumption is about 1 quart in 700mi umless it's driven more aggressively then it uses about 1 quart in 500mi. And it always smells like burning oil while idling at a stop but I don't see any smoke.

[This message has been edited by movin (edited 01-14-2001).]

[This message has been edited by movin (edited 01-14-2001).]

[This message has been edited by movin (edited 01-14-2001).]

[This message has been edited by movin (edited 01-14-2001).]

[This message has been edited by movin (edited 01-14-2001).]

[This message has been edited by movin (edited 01-15-2001).]

[This message has been edited by movin (edited 01-15-2001).]

[This message has been edited by movin (edited 01-15-2001).]

The good news is that your valve guides aren't what's causing the smoke on startup. That's typically either an enrichened mixture (rare on a DME car, unless the engine is stone cold, which yours is) or possible oil seeping past your rings (more likely) or possibly condensation in your engine somewhere (which is most likely). My car has always smoked on startup (an '86).

As far as valve guides go: The chromed versions starting in '86 haven't given me any trouble yet (at 107K). I have heard of later cars still having problems though. This problem plagued the 3.2 series the most, I think.


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Mark Szabo
1986 911 Targa 3.2
1987 Escort 5-speed 1.9
The Porsche Owners Gallery

Originally posted by old_skul:
The good news is that your valve guides aren't what's causing the smoke on startup. That's typically either an enrichened mixture (rare on a DME car, unless the engine is stone cold, which yours is) or possible oil seeping past your rings (more likely) or possibly condensation in your engine somewhere (which is most likely). My car has always smoked on startup (an '86).

As far as valve guides go: The chromed versions starting in '86 haven't given me any trouble yet (at 107K). I have heard of later cars still having problems though. This problem plagued the 3.2 series the most, I think.

The smoke is oil burning, and it seems to happen after sitting for a few days or more. Maybe oil is seeping from the reservoir to the sump up to the cylinder level? Could that could explain the start-up smoke? Why would it just start doing this 5,000mi ago? Bad rings? Would a power chip cause an overly rich mix and lead to wearing out of the cylinder and rings?

Apparently the boxer engine gets oil in the cylinder when it sits. From the sump. Normal. I think you'll find that the oil smoke cloud happens sometimes, and at other times does not. Normal.

My car runs pretty rich during startup, though CIS is different. the smoke looks bluish in the mornings, but is mostly white, gas/condensation smoke. And there's a lot of it. normal, but I wish I could turn down the choke. I may try fidding with the warm up regulator some day.

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'83 SC

The valve guides starting in 1986 were chromed? How could you tell?

Originally posted by old_skul:
The good news is that your valve guides aren't what's causing the smoke on startup. That's typically either an enrichened mixture (rare on a DME car, unless the engine is stone cold, which yours is) or possible oil seeping past your rings (more likely) or possibly condensation in your engine somewhere (which is most likely). My car has always smoked on startup (an '86).

As far as valve guides go: The chromed versions starting in '86 haven't given me any trouble yet (at 107K). I have heard of later cars still having problems though. This problem plagued the 3.2 series the most, I think.

The valve guides starting in 1986 were chromed? How could you tell?

Originally posted by old_skul:
The good news is that your valve guides aren't what's causing the smoke on startup. That's typically either an enrichened mixture (rare on a DME car, unless the engine is stone cold, which yours is) or possible oil seeping past your rings (more likely) or possibly condensation in your engine somewhere (which is most likely). My car has always smoked on startup (an '86).

As far as valve guides go: The chromed versions starting in '86 haven't given me any trouble yet (at 107K). I have heard of later cars still having problems though. This problem plagued the 3.2 series the most, I think.

It says so in Paul Frere's "Porsche 911 Story", and he seems to have at least 98% of the facts about the car's construction correct in this latest (3rd? 5th?) edition of the book. It's an excellent resource for info like this. I can look it up if you'd like, but I remember in specific feeling relieved to find out that my '86 probably wouldn't have problems with the valve guides.

I've heard of others with problems, of course, with models newer than mine. But I've heard *way* more tales of smoke on startup. It's just normal.

If you're really curious about your valve guides, try this experiment once you've brought your car up to operating temperature: Get up to about 5000 rpm in either 2nd or 3rd gear. Release your foot from the throttle and let engine braking slow the car. See any smoke in your rear view? If you do, it's valve guides. If you don't you're good to go. If you see blue and red flashing lights, you picked the wrong area of road to experiment on.

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Mark Szabo
1986 911 Targa 3.2
1987 Escort 5-speed 1.9
The Porsche Owners Gallery

Movin,

There are two possible sources for the occasional puff of smoke on startup, but the oil tank seepage theory is not possible or reasonable, at all! There is simply no way that oil under slight pressure from the oil tank can seep past the gears in the oil pressure pump and get to the cylinders or exhaust system!!!

First, is the oil squirters, and given that there is oil being quirted onto the undersides of the piston crowns as the engine shuts down, if the car is parked on perfectly level ground, then the oil would run down and 'pool' in three or four of the cylinders. Whether seepage past the oil rings is possible or not (and I doubt it) there would be a large amout of oil upon startup the the rings would probably just 'ride up' over a layer of oil approximately 0.001" tall and 1-2" wide at the bottom arc of the cylinder ... and be consumed along with gasoline in the first couple of seconds after the engine starts.

The second source, and most likely is past the exhaust valve guide seals and 'up' the gap between valve and valve guide, then running down the exhaust port into the heat exchangers. Bear in mind that when parked on perfectly level ground, the exhaust valve covers, and exhaust valve seals are 'under oil' after the engine has been sitting for a few minutes. If not entirely level, then some of the valve guide seals will be above oil, and others will be further below the oil level than if on a level surface. The parking angle and length of parking duration are the only variables in this scenario that may be responsible for the variability of the startup 'puff' duration and presence. Remember, the condition of the rings and valve guides is not going to vary from week to week, or month to month, yet the puff phenomenon does vary as to volume of the puff and whether or not it occurs upon startup overnight!

The one thing that should be emphasized is that the 911 engine valve stem seals are not supposed to be perfect ... a certain amount of oil consumption is planned and expected, whether new, or with 120K miles on the speedo, and the 'puff' phenomenon occurs in engines that do NOT have worn-out rings or valve guides, or any trace of oil fouling on the sparkplugs!

In summary, sometimes it happens, other times it doesn't, but really isn't anything to worry about!

If, for some reason, you are concerned about valve guide wear, then check for measurable deflection of the exhaust valves at your next oil change. One at a time, with each exhaust valve opened to a lift of 10 mm, see if the tip of the open exhaust valve can be deflected sideways a visible and measurable amount by pressing on the tip with a large (14" to 18" in length) flat-bladed screwdriver. If you do not have visible side-play, then you do not have a wear problem!

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Warren Hall
1973 911S Targa

Warren,

I have a few questions and I hope you can help. Firstly, why do you say the valve seals are not supposed to be perfect on 911's? Does this mean that a 100% smokeproof 911, even a 993, is impossible if the car is parked on uneven ground or a slope? I have been told that the piston ring theory is possible on new cars as the rings take a few thousand miles to bed in.

Secondly, what is the maximum amount and duration of the smoke on startup in a healthy 911. Sometimes I find that if I park on a grass verge, the car will produce these massive plumes of smoke that lasts for up to 60 seconds or more of driving yet the next day when I park at the same spot there is nothing (btw, its not turbo related)

And finally, a couple of questions unrelated to this topic. Are cracked cylinder heads (at the exhaust port where the guide tip protrudes) safely repairable? And a friend of mine noticed that he had been driving around with the vacuum hose to the distributor disconnected on his 930. How bad is that?

Thanks in advance for any help you can give.

[This message has been edited by 930fan (edited 02-06-2001).]

I couldnt believe that valve guides would be
"chromed"--I re-read Paul Frere and all I could find was reference to chromed valves
for durability. surely one cant run hard valves and hard guides for longlife?
I was waiting for Warren's input but he skipped the guide material subject. Further clarification please, from the experts!!!!
Bob G.

My '88 smokes like you would not beleive sometimes at startup. MUCH more so than the other 2 911's I have owned. I have checked for side to side movement of the valve stem (negligible) decel from 5000 rpm (no smoke). I pulled off the heat exchangers and found no oil in them or around the exhaust valves and stems directly above. My theory is that the cylinders are left with a small amount of oil behind the piston (as in Warrens explanation) and then a worn oil control ring allows this oil to enter the combustion chamber at startup. My engine has a leakdown on all cylinders < 5% which is good, however, that tells you nothing about your oil control ring.
Tom

Bob, I re-checked too, and it's not the guides that were chromed, it was the valves (as you suspected). I assume this means the entire valve, both head and shaft.

I still like the idea of oil seepage past the oil control ring. Seems most plausible to me.

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Mark Szabo
1986 911 Targa 3.2
1987 Escort 5-speed 1.9
The Porsche Owners Gallery