Everybody aware of ZDDP and classic cars?

This has been discussed thoroughly on many different forums, and there is some great info out there. Below is a Popular Hotrodding article along with comments by Bob Mannel, arguably one of the top authorities on the small block Ford engine (he literally wrote the book on it).


Article From: Popular Mechanics Magazine, October 2010 edition.
Car Clinic

By Mike Allen
Q+A
The Missing Zinc:

Q: I had a local speed shop rebuild the engine in my classic muscle car to as new to the original specs as they could, including all-new valve train, pistons, rings and bearings, I pre-pressurized the oil system, and the engine started right up. Within an hour’s driving, the engine started to lose power and misfire. One of the camshaft lobes had failed, making the egg shaped cam virtually round. There was a big divot carved out of the lifter boot. The shop says that I used the wrong oil and that I should have used a zinc additive as well. I used a premium oil, the same one I use in my new car.
A: Ah yes, the missing zinc. Let me start with a primer on zinc/phosphorus anti-wear additives: In the ‘50s, when cars began to feature overhead valves and started making serious horsepower, the camshafts needed more aggressive profiles, which were prone to rapid wear. That’s when lubrication engineers discovered the utility of zinc dialkyldithiophosphate (ZDDP), which had previously been used in motors as an anticorrosive additive in modest quantities. The phosphorus and zinc in this molecule are attracted to bare iron, coating the microscopic asperities (high spots) where the cam nose slides over the surface of the tappet. This molecule- thick layer prevents iron-to-iron contact. After a few hours of operation, the two surfaces burnish each other to a nice, smooth low-friction surface, micro-welding is a thing of the past, and everybody’s happy. Without the zinc and phosphorus, this localized high pressure, combined with the sliding friction, can microscopically weld the cam to the lifter, ripping out tiny chunks of metal. The industry standardized on 800 or so parts per million (ppm) ADDP content in motor oil, and engines lasted a very long time. In fact, ZDDP levels eventually rose to 1200 ppm by the ‘70s.
Cut the 1980s. Cars universally have catalytic converters installed to meet emissions requirement. Somebody figures out that zinc and phosphorus can contaminate the precious metal reactor beds in the cats, reducing their effectiveness. Concurrently, in an effort to reduce internal friction and improve economy, more and more engines use roller tappets or roller rockers, eliminating sliding friction at the camshaft-lifter interface. Even engines that have non-roller-bearing camshafts have better, upgraded metallurgy and improved surface finish at the critical cam lobe-lifter interface. ADDP levels were reduced to 1000 ppm, because the higher levels were no longer deemed necessary.
Now it’s 2010, and emissions requirements are even stricter. ZDDP levels have been reduced back to 800 ppm in the latest generations of motor oil, APE’s (American Petroleum Institute) AM and ILSAC’s (International Lubricant Standardization and Approval Committee) GF-4 spec. Even if some oil gets past the rings or the valve –stem seals in your engine and is drown into the intake through the PCV (Positive Crankcase Ventilation) vent, the cat will remain pristine and your exhaust will smell like buttercups.
And this is right where your ‘60s muscle car gets the shaft. Too little ZDDP, especially in the critical first few minutes of engine operation, can destroy the surface finish of the cam lobes and lifters, especially on the high lift cams, factory or aftermarket grind, used on the really fun cars. Lubrication engineers at Shell say that a stock engine with the original camshaft grind, stock springs with modest seat pressures and OEM-ratio lifters should fine running these 800-ppm oils. Aftermarket grinds, stiff springs and high ratio rockers increase cam-to-lifter pressures and would be better off with higher levels of ZDDP in the mix. Regardless of the petroleum companies’ take on this, most engine builders specializing in these specialty cars like to see that 1200-ppm number.
Back to your problem: Your engine builder should have provided you with instruction as to what oil to use, because there are options. Several companies make boutique oils that meet that high-zinc spec of yesteryear. Amsoil has several oils with appropriate levels of ZDDP in viscosities correct for your car. Some suggest using a modern diesel-rated oil—which I recommend against because there are a lot of additives in diesel oil that aren’t appropriate for spark-ignition engines, and vice versa. If you can’t find anything better at Walmart, however … Many mainstream petroleum companies have an oil marketed for older, high-mileage cars, and it usually has a healthy dose of ZDDP. If you need to know the ZDDP content of any product, ask for the MSDS (Material Safety Data Sheet) from the supplier, which will list everything in the bottle.
My favorite solution for veteran flat-tappet engines has been around for generations: General Motors’ EOS. It was originally sold as an engine oil supplement (get it?) for high-performance engines, and it has the correct amount of ZDDP in a form that wont plug up the oil filter. GM dropped this product a few years back, and I was hording my last six cans. Then it returned as EOS Assembly Lube, Not recommended as a Supplement for routine use, But only for breaking in a new engine. If that’s what it takes to get it past the EPA and onto the shelves, fine. There are other ZDDP products on the market as will. My favorite is Comp Cams’ Break-In oil additive, coupled with the use of GM’s EOS or Comp Cams’ Cam and Lifter Installation Lube.
One final though: It’s easy for the engine shop to blame the oil, but there are plenty of other potential issues that can wipe a cam nose. I like to assemble high-performance engines that have stiff springs, lots of seat pressure and high-lift cams a little differently. I leave out the inner valve spring and even substitute lower-ratio rocker arms for the first few hours. This will substantially reduce cam-nose-to-lifter pressures, reducing wear. After a few hours at lower revs, I change the oil to get out all the wear metal and install the rest of the springs and correct rockers. By then, the cam and lifter interface been broken in properly.
One important caveat: Do not add extra ZDDP additives to an oil that has sufficient ZDDP already on board, in the time-honored American tradition of “if a little is good, a lot more is better.” Excessive ZDDP is corrosive, and the optimal level is right around the 1200-ppm point already in most oils that meet the older standards.
A second important caveat: Oils marketed as racing oils may have a different additive package and may have less detergent, dispersant, viscosity-index improver and other good stuff in them. They’re really intended for racing, and their short drain intervals make them unsuitable for street driven vehicles. To confuse the issue, some products labeled as racing oil may actually contain the appropriate additive package and would be suitable for street use. Castrol GT Racing is one.



And from Bob Mannel...

EPA did not remove zinc to kill old cars. They did it to preserve the service life of catalytic converters.

"Catalyst poisoning occurs when the catalytic converter is exposed to exhaust containing substances that coat the working surfaces, encapsulating the catalyst so that it cannot contact and treat the exhaust. The most notable contaminant is lead, so vehicles equipped with catalytic converters can only be run on unleaded gasoline. Other common catalyst poisons include manganese primarily from the gasoline additive MMT, and silicone which can enter the exhaust stream if the engine has a leak allowing coolant into the combustion chamber. Phosphorus is another catalyst contaminant. Although phosphorus is no longer used in gasoline, it (and zinc, another low-level catalyst contaminant) was until recently widely used in engine oil antiwear additives such as ZDDP. Beginning in 2006, a rapid phaseout of ZDDP in engine oils began."

The primary purpose of adequate ZDDP levels was to form a tough layer to prevent metal-to-metal contact between high pressure surfaces. In our engines that means between the lifter bottom and the lobes of the camshaft. This is absolutely critical during the break-in time for the camshaft when the lifter bottoms and cam lobes are conforming to each other. If direct contact between the metals is made during this time, the two metals have a tendency to gall each other, particularly the lobes. "Galling is a form of surface damage arising between sliding solids, distinguished by microscopic, usually localized, roughening and creation of protrusions (i.e., lumps) above the original surface". ZDDP has little to no effect on pistons, rings, rocker arms, timing chains, etc. where the metal-to-metal contact is of a low pressure nature.

Since all modern engines use roller-type cams, there are no high-pressure contact points inside the engine and ZDDP is not essential, while the life of the catalytic converter is essential to changing nitrogen oxides, carbon monoxide, and hydrocarbons into harmless oxygen, nitrogen, carbon dioxide and water. So, out with ZDDP in oil. It is understandable science and reasonable action in cleaning the air we breathe.

However, our old cars are few, they don't have catalytic converters, and have high-pressure metal-to-metal contact points. We need ZDDP and we are insignificant as polluter contributors. The market has responded to our needs and we have oils available with the right amount of ZDDP we need. But, ZDDP is not a cure for a poor engine rebuild and will not appreciably prolong engine life of low pressure contacts, such as between the crankshaft and main bearings. But, the lack of it could ruin a new camshaft, or shorten the service life of a tappet camshaft after break-in.

 

The discussion of premature cam wear has been around for quite a while. I have read many articles about what can be used and have found that STP pretty much takes care of the problem. The small red bottle contains more ZDDP than the blue one, but either is sufficient to overcome cam wear from what I have found. It is right on the bottle, "contains ZDDP". Someone contacted STP and was assured that there was more ZDDP in their oil treatment than was in motor oil when we ran flat tappets. I only have one vehicle with a conventional valve train and I use STP in it with no problams, so far.