Lead-Light District: Lead Substitutes for Your Classic Cars



Posted: Tuesday, May 20, 2008

by
Classic Vehicle Auction

Classic car restorers have two problems when it comes to fuel: one is that their engine is not too fuel-efficient (and with the rising costs of gasoline, it may be too much of a burden); the other is the fact that age-old classics have engines that relied on lead additives for efficiency.

The Lead Book

Lead additives in fuel were one of the many attempts to tame the unstable nature of gasoline. Since gasoline has a tendency to detonate in high-compression engines (which of course, includes cars), it caused damages characterized by engine pinging noise. Lead additives controlled this tendency, and were thus popularly used as a fuel additive from the 1920s on.

However, later research found that lead was damaging both to human health and to the environment. Thus, countries banned lead additives from fuel, and car companies made engines that are not compatible with leaded gasoline.

The pitchfork and torch campaign against lead additives started in 1973, and cars from 1975 onwards were made with catalytic converters that are incompatible with leaded fuel.

The Score for Classic Cars

While the abolition of lead additives was a good thing, it poses a problem to classic car collectors. The valve seats of many classic cars up to 1975 were 'accidentally' protected from rust and lubricated by lead additives.

The good news is: classic cars can still run on unleaded fuels. The bad news is: running an unmodified classic car on unleaded fuel may cause degradation of the engine. This means that a fully-restored and unmodified '71 Hemi Cuda will need to be protected from rust as well as carbon build-ups, since the engine was designed for leaded fuels.

There are two approaches to protect a classic car's engine: use lead substitutes, or harden its valve seat.

Lead Substitutes

Lead substitutes can be easily found in any car parts or car care store. It sells for $4-$5 per bottle, in which each bottle is equivalent to one full tank of gasoline. The good ones contain Zinc Dithiophosphate (or ZDDP for short). ZDDP is an anti-wear additive, corrosion inhibitor, and antioxidant. Too much of it, however, will damage your catalytic converter, so be sure to buy a substitute with the least amount of ZDDP.

Also, when using lead substitutes for your classic car, be sure to gas up only with premium fuels. Premium fuels have additives that by themselves protect the car's engine from carbon build-ups and other unwanted effects.

Hardening the Valve

Another solution to possible valve seat recession due to unleaded gasoline is to harden the valve. This is an unpopular move, as incorrect hardening will cause more damage than running the car on unleaded gas. An improperly formed valve seat will cause less engine efficiency and more emissions, and may even shorten the engine's life.

Furthermore, valve seats with high nickel content do not need to be hardened, as they are almost the end-result of the hardening process itself. The only upside to hardening the valve seat is that it is a one-step process, which is less expensive in the long run than using lead substitutes.

Leaded gasoline might be poison to our health and to the environment, but it is also the lifeline of most of the classics. If you have a classic car that dates from 1973 below, you better take care of it by using lead substitutes or hardening the valve. And if you are planning to buy a classic, put in mind that in order to keep it in top shape you need to add these things to your budget.


Peter Grizzly is an age-old classic car enthusiast. He makes his living now by being a classic car trader. He owns a third generation Thunderbird, and would like to collect all of the released T-Birds, including the 1954 prototype. His website, which is a classic car auction can be found at: http://www.classicvehicleauction.com
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