January 1, 1986, was a red-letter day for the American public . . . but one that went by largely unnoticed. The first of the year marked a significant milestone in the Environmental Protection Agency's 13-year effort to reduce the level of lead in our environment
Lead — more specifically, tetraethyl lead (TEL) — has been a component of nearly all gasoline motor fuel since 1923, when it was introduced as an inexpensive antiknock additive. It's also been a primary source of lead contamination, accounting for up to 90% of all airborne lead emissions . . . which eventually find their way into the bloodstreams of humans, where concentrations as low as 10 or 15 micrograms per deciliter of blood (roughly 1-1/2 parts per million by weight) can have harmful effects, especially on children.
If you've read the first part of this article (beginning on page 114 of MOTHER EARTH NEWS No. 97), you already know that the EPA's multi-step lead phasedown program was successful in reducing the level of TEL in gasoline from 2.5 grams per gallon in 1973 to 0.50 grams per leaded gallon (gplg) in July of 1985. The January 1st decrease to 0.10 gplg represents a 96% reduction in the amount of TEL used in motor fuel over that period . . . a noteworthy event to be sure, and one overshadowed only by plans to completely eliminate lead in gasoline by 1988.
But the EPA's actions of reducing lead in the environment have also raised a red flag in the face of the owners of some 20 million pre-1971-72 cars and trucks that were designed to operate on leaded gasoline, and have compelled the agricultural community to lobby the U.8. House of Representatives (unsuccessfully) for exemption from the new requirements under the 1985 farm bill. Moreover, the program has caused no little consternation among users of gasoline powered generators, lawn mowers, garden implements, and outdoor equipment . . . much of which, like older autos and tractors, relies on lead in the fuel not only to control detonation, but to provide a lubricative cushion between the valve faces and their seats.
Clearly, the EPA is caught between a rock and a hard place — facing broadsides from a public segment unwilling (and often unable) to bear the economic hardship of replacing costly equipment, while at the same time obligated to serve as the environmental watchdog for the nation as a whole.
To make matters worse, it isn't quite clear at this point what the extent of damage to older engines might be if they were forced to run on low-lead — or totally leadless — gasoline fuels. Aside from the problem of valve recession (which is closely linked to how the engine is used), destructive detonation caused by insufficient octane levels must be considered as well.
Faced with organized opposition, the EPA — in cooperation with the U.S. Department of Agriculture and the American Farm Bureauwill, by the time you read this, be actively engaged in testing older-model tractor and combine engines to determine what effect low-lead and no-lead gasolines will have on mechanical components in hard service. The results of those tests should be available in time for the total lead ban hearings scheduled for mid-1987, and may ultimately postpone the proposed 1988 TEL ban for at least several months.
In addition, another factor is working to buy time for both petroleum refiners and their customers: A "lead banking" provision, enacted by the EPA in March of last year, allowed gasoline manufacturers to produce, through 1985, leaded fuel containing fewer grams of TEL per gallon than required. The "credits" thus earned can be applied to production after January 1986, when the really stringent standards went into effect. In practice, that means that much of the leaded gasoline sold today may legally contain 0.20 or 0.30 gplg . . . a level that, depending upon the refiner, may not drop to the mandated 0.10 gplg until 1988.
The truth is, no one can predict exactly what impact the EPA's course of action may have, because there are too many variables. But there are steps an individual can take to lessen the effect of unleaded fuel on an engine designed for leaded gasoline.
According to the EPA, Amoco Oil Company, and a number of professionals knowledgeable in the automotive field, normal driving with unleaded fuel should pose no serious problems for a car used to running on leaded. But under "abnormal" conditions (which can be as common as trailer towing, heavy loading, or fast driving) valve seat deterioration can and does occur . . . due to high combustion temperatures and physical wear caused by the valve grinding hard abrasive oxide particles into its comparatively soft cast iron seat. Eventually the exhaust valves, the seats, and the valve guides are worn enough to cause dramatic loss of compression.
Moreover, unleaded fuel, though producing fewer hydrocarbons in combustion than leaded gasoline, forms carbonaceous deposits in the absence of TEL that have a greater heat capacity than do lead deposits. Under extreme operating conditions, this can cause pistons to erode or collapse, since it affects their original hardness. Even in the course of normal driving, extended use of unleaded gasoline can raise an engine's octane requirement.
How does all this relate to you as the owner of a leaded-fuel engine? If you're not too hard on your equipment, you can take your chances and use unleaded . . . while checking for telltale signs of valve recession such as frequent exhaust valve adjustment or dwindling compression. If you don't like the odds, write the engine manufacturer to determine if your model and serial number series has been equipped to operate safely on unleaded fuel.
Engines designed to run on leaded gasoline can be adapted, by degrees, to accept the no-lead substitutes. Before even touching a wrench to your powerplant, you might consider switching to a straight-grade, moderate detergent premium oil with some degree of ash content. The "dirty" ash coats the surfaces of the valve face and seat, reducing the physical wear at those critical points. Avoid using ash-free or synthetic oils, since they tend to keep the contact surfaces clean and thus subject to abrasive grinding.
Furthermore, independent laboratories are currently developing lubricative additives to replace the dwindling tetraethyl lead. One such firm, the Lubrizol Corporation, has researched and is in the process of marketing a sodium based additive — PowerShield — for leaded or unleaded fuel. Though their ultimate goal is to supply bulk quantities to refiners and blenders (pending approval by the EPA), packaged retail allotments are already available under a number of different brand names.
If you're committed to a mechanical solution, probably the simplest is to swap heads from a similar later-model engine designed for unleaded fuel operation. Most every auto salvage yard has a copy of Hollander's Interchange Manual, which is something of a bible to those searching for used parts. (In a pinch, you can match up a head gasket from your engine to see if the newer part would fit.) Besides solving your valve-recession problems, use of a later model head will lower your engine's octane requirements, since its combustion chambers have most likely been relieved to lower the compression ratio.
Slightly more involved, but equally effective (especially for engines which don't have an updated, no-lead counterpart), is the use of hard stellite inserts on the valve seats. This is strictly a machine-shop proposition, and its success is dependent upon the thickness of the head casting; some manufacturers use a thin-casting technique in their foundry operations, which precludes the use of inserts. In these cases, induction or inlay welding of a hard material such as nickel into the seat similar to the process used at the factory yields a surface about .060 " thick that can withstand high temperatures and erosion far better than iron can.
While the cylinder head is off, other factors to consider are the use of sodium-filled or stellite-faced valves, hardened steel or bronze valve guides (to check progressive lateral stem movement), and maximum-rate valve springs. Too, the quality of valve seat grinding is critical; the seats must be perfectly aligned with the valve guides, and the valves shouldn't protrude excessively into the combustion chamber. To encourage positive valve transfer cooling, the seat should be fairly wide and be ground to the same angle as the valve face to make a consistent match. Finally, any deposits in the water jacket should be removed, since a buildup of scale or alkaline deposits can greatly influence heat dissipation within the cylinder head.
However, even after you've faced the prospect of valve recession, you can't ignore the possibility of destructive detonation within the combustion chamber. Again, under normal conditions, severe knock probably won't be a problem . . . and occasional "pinging" can be controlled by easing up on the throttle when the ping is audible. But that clatter spells calamity for the pistons and bearing surfaces . . . and can mean meltdown in minutes if allowed to continue.
The solution? Besides avoiding a too-lean fuel-air mixture, proper ignition timing-both initial and total curve-is crucial. It not only keeps detonation in check, but also allows the engine to operate within the temperature range it was designed for. If knocking is a continual problem, try switching brands of fuel; it's an easy way out, and you may hit upon a blend suitable for your engine. Aside from that, you can try installing thicker (not two!) head gaskets, replacement pistons designed for a smooth flame-front advance, and even a water- or alcohol-injection device.
Another more sophisticated approach is that used by auto manufacturers for turbocharged engines: A knock sensor "listens" for detonation signals within the intake manifold . . . and automatically retards ignition timing in fractional increments to allow the engine to operate without damage or noticeable performance loss. (For aftermarket applications, Carter Automotive Co., Inc., St. Louis, MO, makes the Engine Knock Eliminator which retails at automative supply stores for $114.55.)
Of course, the ultimate solution lies with the petroleum refiners and their ability to cope with the federal mandates as they're proposed and issued. At present, gasoline manufacturers are eyeing refinery modifications . . . and using toluene, methyltertiary-butyl ethyl (MTBE), tertiary-butyl alcohol (TBA), and both methyl and ethyl alcohols as blending agents to maintain the octane rating needed by the public. Ethanol, or grain alcohol, has proved so successful in a 10% blend that it accounts for about 601o of all the gasoline sold in the United States-nearly six billion gallons! But the basic common denominator is cost . . . and if we're going to continue to enjoy ample supplies of highoctane gasoline fuel-without relying upon toxic lead to give it that needed boost-we're going to have to be prepared to pay for it.
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