Leaking Valve Seals Actually GOOD for Engine?

[Jelly]

Here's a weird one for you:

As long as you can keep the combustion chamber and assorted parts clean (plugs, valves, etc...), could a SMALL valve seal leakage actually be beneficial for an engine in regards to providing increased piston ring/cylinder lubrication on start-up?

 

[cryptokid]

in theory, sure. but how are you going to keep the rings clean? use some additive every couple thousand miles to free stuck rings? i dont think its worth it really.

also, what are you going to do about the oxygen sensors and cat con's which will foul sooner? i dont know how much sooner but smoeky startups cant be a good thing for them.

heres somthing to think about. early subaru engines as well as the old aircooled vw engines (and even some aircooled porsche) did not use valve seals at all! i know atleast up untill the mid to late 80's subaru did not use valve seals on its exuast valves. aircooled vw's didnt use them on the exhaust OR intake valves. porsche didnt use them on the exhaust or intake as well, but only on certain models.

i have a feeling that the reason was because of the extreme tempatures these engines faced along with the crap oils that were common back in those days. it is not uncommon for a STOCK vw aircooled engines to hit 300-400F cylinder head temps, espically in one of them hippy vans, going uphill.

 

[VaderSS]

Oddly enough, one of the "fixes," for excess valvetrain noise on the LT1, was to put a redesigned valve seal on that had a built in leak.

 

[Kestas]

Our company makes valve stem seals. When I skimmed through the engineering application information, I notice we advertise the seals bleed a measured (or engineered) amount of oil for the needed lubrication of the valve guide.

I doubt it would benefit the piston assy. It would probably get burned before it makes its way to the piston rings. The piston should get all its lubrication from the crankcase splash or mist.

 

[ekpolk]

quote:

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Originally posted by cryptokid:

i have a feeling that the reason was because of the extreme tempatures these engines faced along with the crap oils that were common back in those days. it is not uncommon for a STOCK vw aircooled engines to hit 300-400F cylinder head temps, espically in one of them hippy vans, going uphill.

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OK, this is veering off topic, but I just have to pass this tidbit along. In one of the funniest cases I ever won in court, I represented a kid charged with misdemeanor DUI. The state's case really fell apart when their prize witness testified that my guy blew past her doing no less than 80 mph, maybe more like 90. This happened in 1997. The kid was driving a fully stock, 1968 VW Microbus, with two passengers, uphill no less!!! We had lucked out and got two relatively "hippie looking" guys on the jury, and both actually started laughing during this testimony. I'd guess that the prosecutor's head was at least as hot as the cyl heads in that bus when the jury came back with a Not Guilty verdict in two, yes two, minutes. . .

 

[VaderSS]

Then I'm guessing you did not have TSB 67-61-14B performed, which replaced the valve seals. People who did have that TSB performed found they were using more oil... I have not and will not.

It was perfomed to eliminate valvetrain noise. It was strictly for noise, and the noise did not effect reliability or longevity of the engine.

[ August 04, 2004, 03:31 PM: Message edited by: VaderSS ]

 

[Propflux01]

One reason the VW's did not use seals on their valve was the height of the valve, and the way they sat sidways instead of up and down. The valve was higher than the crankcase, and the valve guide did not have gravity to help oil pull down into the combustion chamber. Also, some vehicles did not use seals on the exhaust valves of anoverhead valve engine as it was felt no vacuum was pulling oil in, and any pressure from leaking valves would push the oil out instead of sucking it in. Also keep in mind any oil entering the chamber will cause engine 'ping' or knock due to the oil burning differently than the fuel. Almost in effect 'lowering' the octane.

 

[XS650]

quote:

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Originally posted by VaderSS:
Oddly enough, one of the "fixes," for excess valvetrain noise on the LT1, was to put a redesigned valve seal on that had a built in leak.

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Vader, I have an LT4 that burns -no- oil. It doesn't budge off the full mark in 6,000 miles. I've had engines before that burned oil at a rate of under 16,000 miles per quart, but nothing like this.

In your vast LT1 experiance, is this likely to be a problem? Seems like something must not be getting lubricated.

It has about 47,000 and runs great.

A recent UOA showed high silicon, lead and tin, but there was an intake leak before the MAF sensor I found a couple thousand miles after I bought the car at 39,500 miles. My next UPA should tell me if that fixed that problem.

An inlet duct wasn't reconnected quite right sometime before I got the car. Since it had a brand new air cleaner element, I think (hope?) the screwup was recent.

 

[SWS]

I can't imagine that any significant amount of motor oil leaking into the intake would be a good thing. I think that it will just gum-up the intake valve(s) and thereby goof-up the air flow, which is critical. I think that I had this condition on my Camry with leaking valve-stem seals. Had it fixed at 40K miles, and the ports were cleaned-out in the process. The car ran with much more power, like new!

Granted that the valve-stems need lubrication! However, I have read that they just need a mist around the top and all will be well... I don't know all of the tradeoffs, but a valve is a really hard, smooth metal that moves only a little bit, with little side-load to the valve guide. It runs hot, but cutaway drawings I have seen always have cooling jackets around the valve area. Given this, I wonder how much lubrication they really need.

 

[brianl703]

quote:

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Originally posted by SWS:
significant amount of motor oil leaking into the intake

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Like what the PCV valve puts into the intake on some engines.

 

[Ugly3]

XS650 - In your vast LT1 experiance, is this likely to be a problem? Seems like something must not be getting lubricated

I agree. It seems to me that in order to "full lubricate" the valve stem seals and cylinder walls a small amount of oil "just has to" get thru the seals and past the piston rings.

I like to see an engine consume a small about of oil, maybe a quart every 5,000 to 10,000 miles. Makes me feel all warm and lubricated.

 

[XS650]

quote:

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Originally posted by VaderSS:
Then I'm guessing you did not have TSB 67-61-14B performed, which replaced the valve seals. People who did have that TSB performed found they were using more oil... I have not and will not.

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Thanks for the clue, I found it with the help of Google

http://www.smokinss.com/TSB/b-body_676114b.pdf

but it doesn't seem to apply to LT4 engines.

That brings up another question. How do you find out which TSBs have been actually been applied to your car when you bought it when it was 8 years old? Does the General have someplace you can find out?

 

[brianl703]

quote:

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Originally posted by XS650:
That brings up another question. How do you find out which TSBs have been actually been applied to your car when you bought it when it was 8 years old? Does the General have someplace you can find out?

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With Ford they have a system called OASIS. Repair/maintenance records from up to two to three years back are all online and can be accessed immediately by any F/L/M dealership. If it was done by a F/L/M dealership it will be in there.

Records prior to 2-3 years ago are apparently archived offline and the dealership has to make a request for them to be put online.

GM dealers are likely similar--I would suggest calling one and see what they tell you.

 

[Ray H]

quote:

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Originally posted by ekpolk:
...The state's case really fell apart when their prize witness testified that my guy blew past her doing no less than 80 mph, maybe more like 90... [in] ...a fully stock, 1968 VW Microbus...

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Shades of the Rodney King beating case in which the arresting L.A. County Sherrifs wrote in their report that King was traveling at speeds in excess of 120 mph in an '86 Hyundai Excell! (I had an '86 Hyundai Excell - maybe off a cliff it could happen... on a good day... with a downdraft...)