More on modern oils.
Torque Talk
Newer Oils With Flat Tappet Engines
Motor oil is the lifeblood of an internal combustion engine, as few would argue. The thin oil wedge between moving parts makes the difference between a healthy engine and disaster. Engines with a flat tappet (non roller lifters) cam such as original Chevelle engines rely on anti-wear additives in oil to keep from destroying lifters and wiping out cam lobes. This is especially true in engines with higher than stock valve spring pressures. The contact point between lifters and cam is very small. Most modern engines manufactured since the late 80's have roller lifters and aren't as sensitive to the anti-wear ingredients in oil.
Problem is, due to API (American Petroleum Institute) findings, anti-wear additives in most oils have been steadily reduced and recently severely reduced again. The primary anti-wear ingredients are (were?) zinc (Zn) and phosphorus (P). Together they make up the anti-wear additive zinc dialkyl dithiosphosphate (ZDDP). But API says ZDDP and sulphated ash causes gradual degradation of catalytic converters and increased emissions, hence the new oil standards. New SM classed oils intended for cat converter equipped gas engine vehicles are to have no more than .08% or 800 ppm (parts per million) of the additives Zn and P. This would include, but not be limited to, all SM classed oils with the API "snowflake" symbol that says "certified for gasoline engines" on the container. Diesel oils (also works fine in gas engines) classed CJ-4 are to have no more than .1% P.
Until recently all you had to buy to be safe for your flat tappet engine was a heavy duty, racing, or diesel oil. Not any more. PLEASE REFER TO THE WEBSITE:
www.lnengineering.com (as in LN) and if nothing else read the chart with test results of different oils and their additive amounts. Look at the amounts of the additives Zn and P in all those oils, the API classification (SL, SM, CI-4, CJ-4, etc.), and the TEST DATE. The LN text recommends a minimum of .12-.14% (1200-1400 ppm) Zn and P for flat tappet engines per a 1977 SAE journal paper on cam and lifter wear in test fleets as affected by engine oil ZDP concentration and type. Though diesel oils such as Shell Rotella T and Chevron Delo 400 15W40 still have higher amounts than most standard oils for gas engines, it has been reduced in the new CJ-4 classed versions. Fortunately the older CI-4 classed good diesel stuff is still being made if you can find it. Some hi-perf cam mfrs recommend it. Advance Auto Parts still has CI-4 Chevron Delo 400 15W40 (in late June). I stocked up.
You could buy expensive racing or synthetic oils but many of those don't have enough Zn and P. But note the Zn and P content of good old STP. GM EOS assembly lube is even higher in Zn and P. That's why it's recommended for break-in of flat tappet engines but isn't cheap and you have to get it at a GM dealer. It's also is very high in detergent which debatably can have a negative effect on the anti-wear additives.
Bottom line is, it's not enough to assume the oil you buy is going to be right for your flat tappet engine, even if it's a HD, racing, or diesel oil. Research your oil before buying. Some oils are now labeled "for off-road use only", which would tend to be better. For summer driving if you can't find CI-4 classed diesel oil (which per the mfr is also fine for gas engines), it looks like using newer CJ-4 classed Rotella T or Delo 400 15W40 AND adding 1 can of STP (red can) or 1 1/2 cans of STP blue can, or 1/2 can of GM EOS would provide sufficient Zn and P (Note: I can't locate any red can STP as of this writing). Or you can pay more for certain racing or synthetic oils, but the important thing is to research it first since some racing and synthetics don't have enough Zn and P. A wiped cam lobe and resultant damage and/or contamination from metal powder can get real expensive.
www.indianachevelles.com/newsletter/July07newsletter/page2.html
