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Engine Repairs and Replacements

Engines are lasting longer and longer these days. But when an engine needs replaced is it better to install new, or rebuild?


Back in the 1970s and 1980s, the average life cycle of an engine was about five to seven years. After 60,000 to 80,000 miles of everyday driving, most engines would develop an oil consumption problem and begin to experience other signs of wear (loss of compression, loss of power, increased emissions, lower oil pressure, internal noise, etc.) Carburetors were partly to blame for the wear because rich fuel mixtures wash the lubricating oil off the cylinder walls and dilute the oil in the crankcase. These older engines were also built much "looser" (wider tolerances) than most of today’s engines, which also increased blowby.

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Consequently, the rings, bearings and valve guides all experienced accelerated wear.

Today, the situation is much different. The average service life of a 1990’s vintage engine is about 10 to 12 years! Fuel injection has all but eliminated the fuel wash-down problem, and much tighter tolerances have greatly reduced blowby and oil dilution in the crankcase. So fewer engines are being rebuilt today as a result.

Improvements in engine technology have extended engine life and reduced the need for engine service. Even so, the current "technology trough" will eventually pass and the numbers of engines being replaced and rebuilt will once again rise. The number of five- to 10-year-old light trucks on the road, for example, has jumped from 18 million in 1985 to nearly 60 million today. Many of these will need engine work before long.


When a customer’s engine needs major repairs, you’re faced with an important choice: You can recommend replacing the engine with a new, remanufactured or used engine, or you can recommend repairing or rebuilding the customer’s original engine.

Replacing an engine with a brand new one is usually too expensive for most customer’s budgets, so the choices come down to a remanufactured engine (or short block), a used engine (and the risks that go with it), or overhauling or repairing the engine yourself. A used engine is a temporary fix at best and only buys the current owner a little more time. Sooner or later, most used engines experience problems of their own and have to be replaced or rebuilt.


Remanufactured engines are a popular option these days because they’re readily available at competitive prices, which has caused a decline in the number of engines being custom rebuilt ("repowered") by repair facilities and machine shops. A quality remanufactured engine can provide good value for the investment, and most come with a 90-day to one-year warranty. Even so, there are still valid reasons for doing your own engine work.

One reason is that rebuilding an engine can be more profitable than replacing it. Assuming the original engine is rebuildable (wear is not excessive and there is no serious damage), and the amount of machine work required to restore it is minimal, you may realize 20 to 50 percent or more profit doing a rebuild versus replacing the engine. Most of the savings (profit) comes from the labor put into tearing down the engine and then reassembling it after any necessary machine work has been done.


The tools required to rebuild an engine are minimal: normal hand tools, some feeler gauges, a torque wrench, and a ring expander and ring compressor. Any machine work that’s needed can be farmed out to a local machine shop.

If the cylinders are worn, they’ll have to be bored or honed to accept oversize pistons and rings. If not, your customer can run a glaze breaker down the bores and do the work himself. If your customers don’t have valve and seat refacing equipment, he’ll have to send that out too. Worn guides can be reamed out, replaced or relined in-house with a few special tools. But jobs such as head resurfacing, line boring, crank refinishing, etc. will have to be farmed out.


Another reason for doing your own engine work is to control the quality of parts and work that go into your customer’s engine – something you can’t control when you buy an engine from an outside source. It may be top quality, or it may not. Some remanufacturers reuse a much higher percentage of parts than others do.

You can also add to your profitability by selling the parts you need in an engine kit rather than individually. A kit gives you everything you need in one box and reduces the chance of mismatching parts. The parts in a kit usually include bearings, rings, pistons, timing chain and gear set, valve seals, gaskets, oil pump, camshaft, lifters and other miscellaneous parts. You can usually get OEM or better quality parts in most kits, which may be better than the parts found in some remanufactured engines.


One aftermarket supplier of engine kits offers a 100,000-mile warranty (including labor) on all of the parts in its engine kits – which is a better deal than you’ll find on almost any replacement engine, new or remanufactured.

The next time you’re confronted with an engine that’s in need of major surgery, advise your customer of his options and the advantages of doing his own work versus replacing the engine altogether. If he has the expertise, the time and a few special tools, rebuilding may be a better alternative for you and your customer.

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