Engine Series: Restoring a Vehicle to Like-New Performance
By Gary Goms
5/21/2008
Power to the People: An independent repair shop has a handful of engine replacement options available: a used engine, a quality rebuilt, a remanufactured or new OE engine.
By Gary Goms
Replacing a worn or broken engine on a customer’s vehicle can be a very sensitive subject for many independent shop owners because it’s a time-intensive and possibly high-liability service. After a replacement is done, a shop’s greatest fear is that a minor ticking noise or oil leak may ruin the profitability of the engine replacement. Nevertheless, engine replacements can be profitable, providing that the service is priced at a profitable level and that the correct precautions are taken to prevent expensive comebacks.
Decision ‘08
An independent repair shop has a handful of engine replacement options available: a used engine, a quality rebuilt, a remanufactured or new OE engine.
When choosing between the used, rebuilt, remanufactured and OE-“crate” engine options, always remember that a used engine might, for example, routinely require an expensive timing chain and guide replacement. However, due to the inherent reliability of some import engines, many nameplate shops feel safe in choosing a used engine as a replacement option.
An example of a typical Ford performance crate engine.
Remanufactured engines are a mixed bag, largely dependent upon core availability, the quality of the OE castings and the quality controls associated with the remanufacturing process itself. As for new “crate” engines, the expense usually eliminates this option for some customers. In some cases, however, the new engine may perhaps be the safest, most reliable option.
One of the many factors involved in choosing an engine are the expectations of the customer, which may include the cost, reliability and durability of the engine replacement. Although the value of the engine replacement may exceed the value of the vehicle, replacing an engine makes good economic sense if the vehicle is in above-average condition or has some other redeeming virtue. In most cases, it’s simply tossing good money down the drain to install an engine in a worn-out chassis. As always, replacing a worn or broken engine is as much of a subjective, as it is a financial, judgment.
Getting the Reman Vote
A quality engine remanufacturer tends to use more components that are new in order to restore original performance. In addition, a quality remanufacturer tends to employ more steps in the remanufacturing process. In the end, higher-quality remanufactured engines generally cost more than lower-quality reman engines.
Much depends upon the nameplate and application, but cylinder head reclamation is a critical point in assembling a quality engine. Because good rebuild cores or new cylinder head castings might be difficult to locate for some applications, a remanufacturer might go to extreme lengths to reclaim, for example, a cylinder head casting. Of course, with modern technology, aluminum heads are relatively easy to reclaim.
The most critical tolerance is the centerlines between the camshaft and crankshaft. The most obvious effect of excess resurfacing on the engine block deck or cylinder head deck is an increased compression ratio that, in turn, can lead to destructive spark knock. This condition can be corrected, within limits, by using a thicker head gasket or installing a head gasket shim.
The less obvious effect of excessive milling is retarding the camshaft timing. As little as 0.010” can, in some engine applications, retard cam timing as much as 3 to 4 degrees. Since an engine with retarded cam timing won’t perform to expectations, the crankshaft to camshaft centerlines must be restored as closely as possible to original specification.
Why the Need For Replacement
Most engines usually fail due to overheating or under-lubrication. A leaking water pump or hose, a clogged radiator, an inoperative fan system, a stuck thermostat or a blown cylinder head gasket may cause overheating. In some instances, a blown cylinder head gasket might be the result of overheating rather than a mechanical failure in the gasket itself. In some rare instances, loading and driving the vehicle beyond its rated capacity may cause overheating.
Conversely, under-lubricated engines may be the victims of an oil leak or neglect. Although oil leaks are rather obvious, driving a vehicle without checking the oil or without changing it at scheduled intervals implies owner neglect.
An engine with a heavily sludged lubricating system usually suffers from premature wear and, occasionally, catastrophic bearing failures caused by clogged oil pump screens or oil galleries. Heavily sludged engines may also tend to have application-specific lubricating problems in some areas of the engine, including valve and camshaft oiling.
Insufficient oiling, on the other hand, often results in the overhead camshaft seizing in the cylinder head, the timing belt breaking, and interfering intake and exhaust valves bending. Insufficient oiling also may cause crankshaft damage and severe piston scuffing.
A Chevy custom engine build can be an eye-catching powerplant for a customer’s vehicle.
Many shops lose money because they estimate a partial, rather than a complete, engine replacement. Under-estimating the engine replacement usually causes the shop to write off many billable hours in order to resolve these otherwise avoidable misunderstandings with the customer.
Since a replacement engine is usually priced at a very low profit margin, and considering the warranty liability, the long installation times and other contingencies that go along with an engine replacement, profitability can be very low or, in some cases, non-existent.
The true profit in an engine replacement is found in the add-on items required to restore the engine support systems and drivetrain to like-new performance.
When estimating an engine replacement, don’t forget that new spark plugs, wires and, if applicable, distributor cap and rotor are recommended.
For example, during the estimating process, extra time should be included for cleaning parts, removing broken studs, refinishing warped manifolds and road-testing the finished product. In addition, a wheel alignment should be included if the front suspension is disassembled or the engine cradle is removed during the replacement process.
When estimating an engine replacement, it’s important to remember that oxygen sensors may be contaminated with antifreeze or oil from the old engine. If the old engine was severely overheated, it’s a safe bet that the calibration on the temperature gauge and engine management coolant sensors has also been ruined. Along the same lines, don’t forget that new spark plugs, wires and, if applicable, distributor cap and rotor are recommended, especially if the engine is a 1995 or newer model equipped with an OBD II misfire monitor.
Here’s a Big-Inch Cadillac custom engine rebuild that’s ready to ship.
The catalytic converter also may be ruined from a misfire condition or contaminated with antifreeze or oil, so it’s wise to leave the estimate open for such contingencies, especially when operating in an area that requires an annual emissions test.
When the intake manifold is removed, the exhaust gas recirculation (EGR) passages should be cleaned to make sure that the EGR flow is adequate and distributed evenly among the cylinders. If this basic procedure isn’t
performed, the on-board diagnostics may later discover the fault, store an EGR failure code and illuminate the Check Engine or Malfunction Indicator Light.
Other Pricing Notes
Be sure to include expendable items like timing belts, drive belts and tensioner pulleys in the estimate. Many reman engines, for example, are shipped without timing belts. If the engine is used, a timing belt replacement is recommended, especially with the engine out of the chassis. If the engine is a valve interference type, a technician simply can’t afford not to replace the timing belt with a fresh unit simply because of warranty considerations.
Also, if the old engine has suffered catastrophic bearing failure and is equipped with an engine oil cooler, the probability is very high that the cooler itself is heavily contaminated with metal particles. The best option is to replace the oil cooler to avoid ruining the new engine.
A specialty machinist at Gessford Machine, Hastings, NE, spends significant time final polishing the
aluminum details on a Paxton Super Charged 427 Shelby engine.
Cooling system component sales usually are neglected because a shop is trying to keep the cost of an engine replacement affordable. While it’s true that every job has to balance affordability with reliability, it’s also true that a clogged radiator, badly deteriorated hoses or a worn water pump can cause the new engine to overheat and possibly fail.
Radiators are always a prime candidate for service or replacement, since the old engine may have been overheated. When overheating occurs, sediment from the engine’s water jackets may partially clog the radiator core, which reduces the cooling capacity of the radiator. While this condition may not be obvious at first, it may come back to haunt the engine installer on a hot summer day. In the extreme case, the engine replacement may be ruined, especially if the driver doesn’t keep an eye on the temperature gauge.
At the very minimum, the radiator should be cleaned externally and flushed before doing the engine installation. In addition, the correct mix of factory-recommended coolant should be installed to ensure against the coolant boiling away or a freeze-up occurring during the cold days of winter.
After the new engine is thoroughly warmed up, always make sure the engine cooling fan(s) activate when the coolant approaches specified maximum outlet temperature. In some cases, the cooling fan may have two speeds, with the slower speed activating when a normal temperature increase occurs, and the second speed activating when the coolant temperature exceeds a specific threshold or when the air conditioning is turned on. When all systems are “up and running,” the complete engine replacement is ready to roll out the door with your full confidence that it will perform to the original manufacturer’s specifications.
Remanufactured engines are a mixed bag, largely dependent upon core availability, the quality of the OE castings and the quality controls
associated with the remanufacturing process itself.
Engine blocks are generally resistant to heat and lubrication damage. More commonly, an engine block might develop fatigue cracks between cylinders or around main bearing journals, which renders the block unserviceable. A worst-case scenario might include spun main bearings, which requires the main bearing journals to be align-bored.
Unfortunately, align-boring, like excessive block and head milling, reduces centerline dimension between the crank and camshafts, which retards camshaft timing.
Although over-boring the cylinders can cause overheating and excessive oil consumption, most remanufacturers now hone the cylinders to accommodate piston oversizes amounting to much less than the standard 0.030” oversize bore.
Torque plating, which duplicates the stresses and distortions in the cylinders caused by tightening the cylinder head to the engine block, involves installing a heavy plate resembling a cylinder head gasket to the engine block. Torque plating is critical for correct cylinder refinishing on some engines that use low-tension piston rings.
The most common oversight in cylinder block preparation is the failure to remove hardened accumulations of core sand and sludge in the cylinder block water jackets, which can cause future overheating and radiator clogging problems.