Fill the oil filter and the oil pump with oil prior to startup to create instant oil pressure. You can’t prime the engine with a drill the same as a V8, but you can crank the motor for 15 or so seconds with no plugs in to distribute oil and raise the pressure. Cranking it over with no plugs removes any load from the engine bearings which is very desirable. It’s also a good idea to pour some oil over the cam, valve train, and front chain. Worried about cam break-in? Just turn the motor over several times without plugs before you reinstall the rocker arms.
Oil Weights and Brands
Despite what your old manual says, don’t use 10W-40. It was common in 1974, but no new car engine today uses it. Instead, use 10W-30. Because it’s thinner, it will free up a couple of horsepower, rev faster, and will reach all bearing surfaces more quickly. We consider Castrol 30W the best single-weight, Castrol 10W-30 the best multi, and Mobil1 10W-30 the best synthetic. For a higher ZDDP level oil, Valvoline VR1 racing oil is the oil of choice in L-series engines.
The quality of the oils used today versus what was available in the 1970s is night and day. Back then they sludged up motors and filled oil pans with glop. Today’s SM API-rated oils have much more detergent and anti-varnishing abilities and are said to be stable out to 10,000 miles. It’s amazing so many Z engines made it to 200,000 miles using that oil. It really says something about the quality of the engines as a whole. HOWEVER...older engines with mechanical valve tappets like the L-series and V8s with flat tappets (not roller cams) were designed for motor oil which contain a moderate amount of zinc and phosphorus known as ZDDP (zinc dialkyldithiophosphate). ZDDP is considered a miracle lubricant for engines and has been used for about 60 years in motor oil and greases worldwide.
While zinc is not directly harmful to the environment, if it is burned due to ring blowby, it ruins your catalytic converter. So over the last decade, the EPA has pressured the oil companies to reduce the percentage of ZDDP in their passenger car oils. This extends the life of converters which, in turn, reduces total car emissions. SM-grade oils all have about .08% ZDDP to conform to EPA standards, while 2% and higher ZDDP is considered the level to shoot for.
Pressure from the construction industry allows some diesel oils like Rotella T, made by Shell, to use higher levels of ZDDP, which they claim is needed on heavy equipment. However, we don’t like the idea of using bulldozer-grade oil in a 7,000 rpm L28, even if it does have zinc. Starting in 2007, construction equipment has tighter emissions standards, so zinc in Rotella is likely to diminish eventually.
Luckily, there is still one company with the gust to market a higher ZDDP oil for passenger cars in a viscosity that doesn’t reduce horsepower: Valvoline. Their VR1 10W-30 racing oil is a quality SH-grade oil, which simply means the ZDDP hasn’t been removed to qualify as an SL or SM grade. Valvoline’s MSDS sheet lists it as 1.3% phosphorus/zinc, 1% sulfated ash, and 2.5% calcium, which makes for a nice lube cocktail. Valvoline states it exceeds SM levels of protection, so this is now our oil of choice. The best place to find it is at NAPA stores. It also comes in a 20W-50 version, but that may be too thick for an L28 motor.
Oil filters don’t increase horsepower or make the engine breathe better; they filter the oil. The particle size considered to cause the most wear is said to be around 10-30 microns in diameter. What you need is a filter which can reliably filter the smallest particle size from your oil supply. Be careful using racing oil filters as many are designed for maximum flow by allowing everything up to 50 microns or so to pass into the engine, which is fine if you tend to rebuild your motor every season.