Fawndeuce

I just changed the valve stem seals on my '67 300 because the plugs were getting some oil, especially the #7 that was bad.
The engine had been rebuilt several years they had only used the O ring seals.
Valve stem play didn't seem too bad to me, but the seals were brittle and dried out, the #7 had none at all on the intake.




Paul

midyearvette

that is possible if the seal was left off an intake valve, exhaust valve, not so much as the stems and guides are never under as much vacuum as an intake valve, if any at all
this is not to say that is your entire issue with the fouling plug.....

67vetteal

Time to do a Compression Test. Also, you did not mention if you are seeing blue smoke when engine is first started. This would be a sure sign of Valve Stem oil intrusion. Al W.

Plasticman

Chevy did not use anything other than the square cut "O" ring seals (and splash shields under the retainers). So any additional seals were aftermarket installed on the older engines.

Obviously no seal at all means more oil flowing down the stem. Do you have the splash shields? If not, then you must use the PC type seals (seals that are installed over the upper guide boss) or install the splash shields.

Note that too much oil flowing down the intake stem will also result in oil/carbon caking on the backside of the intake valve (potentially reducing air/fuel flow through the valve).

Plasticman

Fawndeuce

I used Felpro SS72526 exhaust & SS72527 intake John, as had been recommend when I asked here a while back.

Any chemical way to clean the crud out without pulling the heads?
Based on the way the #7 plug looked when I bought the car, probably the intake stem and the piston top look like the surface of the moon.



Paul

Plasticman

Paul,

I don't know any effective way of removing the crud, other than head / valve removal. Even then (depending on the amount, and I have seen some horrendous), a motor wire brush will be needed or some time in a hot tank. Cold solvents don't touch it (at least the ones I have used).

Note that engines that are "abused" tend to keep the backsides of the intake valves cleaner (the granny driven vehicles tend to be the worst). But once the crud has appeared in any sizable amount, higher power levels and rpms won't help much.

Plasticman

Westlotorn

In 1966 it was pretty normal for engines to use a quart of oil every 800 to 1,500 miles.
Using modern rings and good valve stem seals this changed to 1 quart of oil in 5-15,000 miles so an upgrade to good quality valve stem seals can really help.
The Sealed Power Ring Engineer in the 90's told me a single missing valve stem seal can use 1 quart of oil in 400 miles so they are important for oil control, I hope this helps.

Westlotorn

Old dried up valve stem seals do break and fall off, you find them in the oil pan most times.
Rubber based products all age and eventually will fail. At least they are not too hard to change.

Fawndeuce

I think it's worse on these old cars that get driven so infrequently and then sit all winter.
I've had to change them on every old car that I've bought, even though they'd all had engine rebuilds a few thousand miles prior.
The common element was that they had all sat for several years after the rebuilds and had been rarely driven.



Paul

wmf62

oil seals biggest enemy is heat; heat makes them brittle, not the oil.
Bill