Teflon Valve Stem Seals

[C9]

What kind of life expectancy can you expect with these when running on the street?

The 32's 462" Buick engine has good compression and is in a good state of tune, but I'm pumping a bit of black smoke on hard acceleration and am leaning toward a valve stem seal problem.

The carb's set up ok and in fact, the float levels were just checked a while back - 750 CFM Edelbrock fwiw.
In fact, the carb is jetted leaner than stock for the altitude where I live now.

[enjenjo]

As long as the Valve guides are good, they seem to last forever.

I just had the heads redone for my 300 Buick, and when they were disassembled there were no valve seals in it. Also, the books don't show a valve stem seal for it. The gasket kit had seals in it, but they won't fit without machining the guides. My machinist tells me I don't need them on a Buick, because the valve guides are taller. So it's going together without stem seals.

[C9]

Your machinist's recommendation is interesting.

Seems like oil's flying around inside the rocker covers pretty good and guide height wouldn't make too much difference.

I was going to use the stock 455 seals, but the K-B springs are doubles and the stock seals only fit a single spring.

I've been keeping the redline at 5000 rpm and seldom run it over 4200 rpm.

With the mild cam I'm running in it - 260-266 degrees adv duration - and keeping to the low 5000 rpm redline I think the stock Buick single springs would do it.

Long as I don't get into harmonics problems like my little brother did with the single springs on his DRCE engine.
He was breaking a spring - or two - on every run.
7500-8000 rpm redline on the 500 cid engine.

He was given a set of springs with a harmonic damper and now shifts the engine at 9000-9200 rpm and broken valve springs seem to be a thing of the past.

I wonder too if anyone's ever found the Teflon seals up on the valve stem and off of the valve guide?
The guides were cut with the correct tool and fit nicely when installed.

Maybe I just need a new set.
Easy to install with a source of air pressure....

[Bruce Dorsi]

There are two types of Teflon valve stem seals.  ....One style is made entirely of Teflon.  ... The other type is made of Viton with a Teflon wiper ring.

I believe the all-Teflon seals will work great on a race engine, but I don't recommend them for a street engine.  .....The all-Teflon seals do not have the elasticity to return to their original shape, and will actually take a "set" to their operating condtions.  ....Street engines will normally have some play in valve-stem-to-guide clearances.  The Teflon seal will actually become oval where it rides against the valve stem, and will then allow oil into the guides.  ....Teflon seals also "harden" with exposure to heat, hot oil, and age.

IMHO, the Viton seals or Viton/Teflon seals are better suited for street engines.   ....(Do not confuse these with umbrella-type seals.) ....These seals are similar in shape to the all-Teflon seals, and are fixed to the valve guide.  .....There are many OEM applications of this style for GM engines.   ....I believe Fel-Pro has the largest selection of sizes of this type.

If the O.D. of your valve guide bosses are straight and smooth, you may be able to find a seal which will not require further machining of the guides.   .... I'm not sure, but I think the sizes available can be found at Fel-Pro's website.

Some people prefer not using stem seals on exhaust valves, as the  oil provides some extra cooling and lubrication for the exhaust valve.  ....Many GM crate motors use the positive-type valve seals on both intake and exhaust.

The intake valve guides are constantly exposed to manifold vacuum.  ....Failure to use seals on intake valves seems questionable to me.

One other thought:  ....I can't imagine oil leaking past the guides causing BLACK smoke.  ...I've only seen blue smoke from oil consumption (non-diesel, of course!).  ....Could your black smoke be caused by additives in your fuel?

[C9]

Viton rings a bell, but I'm not sure.

When I bought em I bought 20 so I'd have a couple extra's for the one you screw up and the other one that rolls under the bench never to be seen again.

Been trying to find the old ones, but can't.
Evertime I think my new garage is pretty organized, I find it's not....

[Skip]

Teflon doesn't have any memory, period.  Stretch it and it stays stretched.

[C9]

Thanks Skip.

I oughta just get in there and yank the rocker covers and see what I can see.

Since I don't rev this engine very high and the K-B valve springs would be useful in the other - higher horsepower, I hope - Buick engine they could be put to more use there.

A standard valve job, some stock single springs and stock umbrella style valve stem seals on an extra set of heads and steal the "good" head off the 32, do a bit of freshening up may be a good way to go.

The 32 is running a mild cam - 260 - 266 degrees advertised duration - and the 31 will run a 288 - 294 adv duration cam, the 31 could make use of the good stuff.
Provided a spring tester shows the springs up to snuff....

[DRD57]

Back when I was running a street/strip 440 MoPar, I put the teflon seals on it because it was the "trick" racer thing to do.  I soon found out that the perfect seal prevented the exhaust guides from being adequately cooled and lubricated and the guides themselves wore quickly.

I then found out that the best arrangement was teflon seals on the intakes and no seal on the exhaust. Sure it smoked just a little bit even when fresh but the guides lasted a lot longer.

[enjenjo]

Jay, sent you a PM

[C9]

Jay, sent you a PM

PM'd you back.