To quote Oklahoma's favorite son: "All I know is what I read in the papers." I'm just going by what the cam manufacturers have published regarding flat tappet cams and perhaps it's an over simplification, but I still believe I'll follow it.

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David Kight
'62 Valiant Signet, White
'98 Dodge Dakota
'06 Jeep Liberty

Growing older is unavoidable but growing up is strictly optional.

Oil consumption by the slant six in my truck has been steadily decreasing since I began driving it regularly. Fairy tales can come true...it can happen to you, if you're young at heart...Davey

Very likely, if the additive is chosen carefully and used in thoughtful proportion. The ZDDP additives are available in pint or quart bottles (the type sold for new-engine break-in). GM offer it as "EOS" (Engine Oil Supplement) under p/n 88862586, and it seems adding some at each oil change would provide the extreme-pressure protection missing in SM oils without much of any chemical incompatibility risk, and without buying more costly exotic oils.

How much to add?

Well, the SM spec stipulates Zinc and Phosphorus content of 0.06% to 0.08% (600 to 800 ppm). GM EOS contains 5762ppm Zn, and 6221ppm P, or 0.6%. That means in a quart of EOS, you've got about 0.192 ounce of Zn and P. It's been well documented that a 0.10% to 0.12% concentration of Zn and P is optimal for flat-tappet engines, for example in SAE papers 770087, 831760, and 2004-01-2986.

To achieve 0.11% Zn and P in a 5-quart system, we would want 0.176 ounces of Zn and P. There's 0.192 ounce in a quart of EOS, but there's also 0.08% Zn and P in a quart of SM engine oil (actually, most of them run a little on the high side, as it seems, but we'll use the 800 figure). In 5 quarts of SM engine oil, therefore, you've got 0.128 ounce of Zn and P. Therefore, you're a little under 0.05 ounce short of what you want. Doing out the maths and remembering that I've been rounding pessimistically, 8 ounces (1 cup, i.e., half a pint) of EOS would bring most any SM engine oil back within the optimal Zn and P content. Which means that a quart of EOS would last you four oil changes. A quart of EOS lists for over $19, but can be had for $13 or so from a friendly parts department or GM Parts Direct. So, the added cost per oil change would be less than $4 even allowing for shipping charges.
So-called oil "stabilizers" (STP, Lucas, etc.) are mostly just motor snot, the kind that sleazy used-car dealers have been spooning into crankcases to quiet worn engines and temporarily stop exhaust smoke since your grandfather was in the market for his first car. See here for the real story on the damage these "stabilizers" do.

Most of the data for this post came from the tables and charts here, by the way.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

Wow! That post is a keeper. I will absolutely print that out and file it away. Thanks.

Sam

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Lets say that I'am unsure if my oil has the reduced "good stuff" (zinc/phos) Maybe the label is missing or I am to dumb to know what to look for on its label. Would it be a bad idea to add the one cup of additive to any oil change? It may not be nessasary, but would it be harmful?

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67Cuda,FAST EZEFI,340cu,CR=10.25,RollerCam&Rocker (XR268HR,#20-810-9)(#1622-16)(EddyRPM#60779,#7576), (MSD6AL,#6425) A904, GearVendorsOD, 8 1/4,3.55:1, ClassicAir

Most all oil on parts store shelves these days is "SM" rated. Check your bottle on the back label for the ring-shaped service description, and you'll find something like "API SM" or "API SL" or "API CJ/SM".

You wouldn't hurt anything if you added a cup of EOS to a pre-SM oil.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

I really don't like air OR the rope. Air because it turns you cylinder into a pnumatic mouse-trap for the valves, and the Rope: because rope doesn't belong there. I just turn my engine to where #1 is at TDC, then I compress & remove the springs. Just let the valve set on the piston! It works, 'cause I've done it, and it's safe. It's by far the fastest way. You can do #1 and #6.....rotate and do #2 and #5, rotate and finish with #3 and #4. I'm kind of suprised that someone else doesn't do this.
That's my $0.02.....

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225 Cubic Inches of Iron-Head American Muscle

225 bored .040 /.100 off block, Schneider Cam 224@.050~ .480 lift - Stock valves, blended bowls, Offenhauser intake with 500 Edelbrock carb

Neither does a piston stop belong in the spark plug hole, nor a degree wheel on the crank snout, but people put those in when they're degreeing-in camshaft. As with the rope, all you have to do is remember to remove the tool before starting the engine, and as long as you keep your mouth shut and don't go blabbing all over town, nobody will ever have to know that you temporarily inserted a service tool into your engine via the spark plug hole. Shhhh!

Doing it your way (let the valves rest on the piston head) makes it a damnuisance to put things back together. Much easier with the rope trick.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

Back on track here...

Compress the valve spring with the appropriate tool. I've got three that I hate at differing levels depending on what type of head I'm going after. Once the spring is compressed, remove the keepers from the valve stem. if there is still a seal there, remove it or at least the big chunks. Clean things up, install the new seal. Some of them come with a little plastic tube for you to slide the new seal into place. I use a bit of white Lithium grease. There should be a suggested lubricant with your package of seals, or perhaps a manual of some sort will detail this.

Put your spring back in place, depending on the type of compressor your using, most likely something that performs like a vice grip with a cam, only whimpier, install the keepers, put a little tension on them with the spring retainer, and release the tool. Everything should stay put.

It's not that bad of a job once you get into the rhythm of it.

CJ

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Part of Tyrde-Browne Racing

Now for the million-dollar question: What's the favored brand?

I figure I'll go ahead and do it, even if for nothing else than preventative maintenence.

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'74 Duster w/ HEI ignition, beat to snot suspension, A904, 8.25" 3.55 SG rear, still being tuned up and gets 17 MPG

Know how they always build a better idiot? That's me

OEM or your favorite parts store. I've not had any problem with any of the suppliers.
Seals tend to live quite a while, except in overheat conditions. They'll get hard and brittle after a while. Since it isn't that hard to do, just knock them out every five or ten years. If they come off soft, your ahead of the game. If you have a high heat condition, or your doing any major work, just take care of it. They're cheap, and your there.

CJ

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Part of Tyrde-Browne Racing

There is a differance; you can remove those two things, and be assured it's off the engine(I hope). And they are designed to be used in the manner described above. You can't tell what kind of rope fibers are left in the cylinder. It may not hurt a thing, but I like to ere on the safe side.
I guess that's a challenge?? I'll race you rope vs. "TDC" anytime! Get out your stop-watches...

Back to topic:.....Jopapa, I have a set of NEW valve seals you can have for the cost of shipping. I went with Teflon seals, so I don't need the one's that came in the kit. (Some guys would rather just swing by the part-store, but I thought I would offer. PM me if you want them)

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225 Cubic Inches of Iron-Head American Muscle

225 bored .040 /.100 off block, Schneider Cam 224@.050~ .480 lift - Stock valves, blended bowls, Offenhauser intake with 500 Edelbrock carb

Sure ya can. If you use Nylon rope, which does not shed fibres, there are no fibres left in the cylinder. If you use cotton or hemp or jute rope, which can shed fibres, there might be small fibres that will burn to light ash and be blown out the exhaust the very first time that cylinder fires. Either way, you are getting scared over nothing.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

Jopapa, you may want to try a careful engine flush, which will often help reduce oil consumption if you've got stuck rings contributing to the problem. But, keep in mind, older engines will generally lose (leak/burn) more oil than newer engines, so you're probably not going to achieve new-car levels of oil control until you rebuild the engine sometime in the distant future.

Also: Have you replaced the crankcase breather?

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

Wow, sounds like you've got a helluva procedure down for flushing your engine. I'll have to give it a go and see if it gets anything out. I confess I used a can of Napa's flush compound last time I changed my oil (when I first bought the car) and what came out was black as night. Though I'm losing oil one way or another, what's in there is still clean looking, so I take that as a good sign. When I do the valve lash (hopefully soon) I'll check those seals and see how bad of shape they're in. It's also got a new breather and a new PCV valve.

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'74 Duster w/ HEI ignition, beat to snot suspension, A904, 8.25" 3.55 SG rear, still being tuned up and gets 17 MPG

Know how they always build a better idiot? That's me