1. What oil do I need and what do those ratings mean?
There are several ratings assigned to motor oils by the American Petroleum Institute (API). The newest ratings (SM and SN) always supplant older ones and are backward-compatible for engines, meaning they’re approved for use in anything that was covered by the previous generation of oils. If your engine uses a roller cam, no sweat, you’re fine with the modern oil of your preference.
The issues for rodders arise with flat-tappet cams as modern oils have much lower levels of ZDDP (zinc dialkyl dithio phosphate), which is the key component for cam and lifter wear prevention on flat-tappet cams. Modern oils use roughly one quarter of the pre-1990 level of zinc and phosphorus to meet the EPA’s emissions standards and requirement of 100,000-mile catalytic converters. That amount of ZDDP doesn’t allow for much of a sacrificial coating to prevent metal-to-metal contact. Guys with modest engines with small cams and low spring pressure may get away with it; guys making real power likely won’t.
Pages could be written on this topic, but we know all you really want to know is what goo to pour in. Unfortunately, it’s not as easy as looking for generic “racing,” heavy-duty, or diesel oil, since that labeling doesn’t specifically mean they have the additive levels needed. The simplest answer? Buy oil from the guys who hang their hats on racing and produce oil specifically designed for flat-tappet engines with aggressive lobe designs and high seat pressure. You may not find it at Wal-Mart, but there are plenty of options; AMSOIL, Royal Purple, COMP Cams, Valvoline, Kendall, Brad Penn, and Joe Gibbs Driven all have oils available that provide ideal levels of zinc and phosphorus for flat-tappet engines. AMSOIL’s new Z-Rod oil, for example, is specifically formulated with high zinc content for flat-tappet engines.
Alternatively, a specific additive like ZDDP Plus can bring just about any modern oil to safe levels, though it obviously can’t offer the benefits of a specifically blended additive package designed to work with a specific base oil.
One more tip for flat tappers: opt for COMP Cams’ Pro Plasma Nitriding surface treatment on your cam. Nitriding increases the cam’s hardness by about 15 points on the Rockwell scale, which will help significantly during break-in and wear.
2. Wiring: When is it time to replace?
The first and most obvious thing to look for here is the general condition of the insulation and the wire itself. If the insulation is dry, cracked, or broken, or so petrified that bending it snaps it, well, that means the wire is likely done on two levels. Broken insulation obviously results in the increased chance of short circuits and fire, but it also means that the wire itself may have been exposed to moisture-causing corrosion. Corrosion is sneaky too; once it gets started it can travel up wires, even under the insulation. That results in less electrical conductivity, more resistance, and probably more heat—none of which are good.
The second thing to consider is: How much electrical equipment are you going to add? EFI, gauges, power accessories, and other various modern electronics were never considered in anything pre 1980s, so the odds are the capacity (physically and electrically) of the fusebox in anything older isn’t up to the challenge. There likely won’t be extra fused slots available, so you’ll end up stringing new wires and building out auxiliary circuits with their own external fuses and relays to safely add on some of your upgrades. You’ll quickly end up creating as much work for yourself as just replacing everything from the get-go. Fortunately the aftermarket has kept up with the pace, and model-specific kits are available from American Autowire and Painless Performance for many popular vintage cars that make the process much less intimidating.