A vehicle restoration is the process of reconditioning it from a used condition "in an effort to return it to like-new condition ... it can be refurbished using either original or reproduction parts or techniques." The objective is to preserve the historical aspects of the vehicle, its components, and assembly.
Restoration starts with research. You have to thoroughly know the vehicle and have a list of resources available for the correct components. In addition, you need a team of highly skilled craftsmen passionate about the process.
A complete restoration includes not only repair of the parts
that can be seen – the body, trim, chrome, wheels and the passenger
compartment – but also the components that are not necessarily visible or
otherwise evident including the engine and engine compartment, trunk, frame,
driveline, and all ancillary parts like the brakes, accessories, engine cooling
system, electrical system, etc. Repairs must be made to correct obvious problems,
as well as for cosmetic reasons. For example, even if a wheel is covered by a
full hubcap and not seen, and is structurally sound, it should have the tire
unmounted and any required repairs performed such as rust removal,
straightening, priming and painting. Its attention to detail every step of the way.
A complete automotive restoration should include total removal of the
body, engine, driveline components and related parts from the car, a total
disassembly, cleaning and repairing of each of the major parts and its
components, replacing broken, damaged or worn parts and complete re-assembly
and testing. As part of the restoration, each part must be thoroughly examined,
cleaned and repaired, or if repair of the individual part would be too costly,
replaced (assuming correct, quality parts are available) as necessary to return
the entire automobile to "as first sold" condition. In may cases components when parts no longer exist, they have to be fabricated from raw materials.
The interior of the vehicle should be examined and repaired or replaced to match those that were available from the factory. The seats must be repaired before being re-upholstered and the coil springs repaired, replaced, or retied. The instrument panel, or dashboard contains a number of gauges, each of which have to be inspected and cleaned, repaired, or replaced to be brought back to both operational and cosmetic standards of the car when it was first sold.
Developments in technology have made it possible to salvage the original automobile's interior by various restoration processes. Examples of this include leather seat, dash, console, steering wheel, door panel, and trim repair as well as re-dyeing.
In a complete restoration, the repair and refinishing of the car's body and frame must again go through the careful inspection and subsequent repair, and re-coating as necessary to bring the car to as first sold condition.
As part of the automotive restoration process, repair of the car's frame is important since in serves as the foundation for the entire car. The frame should be inspected for straightness, twisting, alignment, rust damage, stress fractures, collision damage and condition of the mounting points for the body, suspension, and other components. Any problems must be repaired, which can be a costly process. For many popular cars, replacement frames can be purchased from parts suppliers specializing in that make of vehicle. This is often a better option than investing money into a severely damaged frame. Depending on the frame construction, mud and water can make their way inside the frame and cause rusting from the inside out, so it can be seriously weakened with little or no external sign. This, and the fact that many replacement chassis/frames are galvanized, provides sound additional reasons to consider a replacement frame.
If rust is present on a body panel, the panel was damaged by a collision, or other damage is present, there are several options for repair: fix the damaged panel (minor damage), replacement (excessively damaged panels), or cutting out and replacing a portion of the panel (moderate damage - for many makes of vintage car, small partial patch panels are available and designed to be welded into place after the damaged portions are cut out). Although this may seem simple in principle, in practice it is highly skilled work. One of the highest skills in restoration is the use of the English Wheel or Wheeling Machine to fabricate complete compound curvature panels from scratch. Many panels, (especially if from different sources), may be a problem to fit together and need reshaping to fit together properly. Variation in panel size and shape and 'fettling' by skilled metalworkers on the factory production line to make panels fit well used to be common practice, especially with British and Italian sports cars. Even genuine New Old Stock factory panels may require panel adjusting skills to fit.
The entire engine and all related systems are inspected and whatever is necessary to get them into original condition is done. The engine and all of the ancillary components – starter, generator/alternator, radiator, distributor, carburetor and all others – must be inspected and corrected to factory specifications. The engine itself, plus the transmission, clutch, overdrive unit, and even the driveshaft must be meticulously inspected, cleaned, and checked for wear. This will show up as deviation from original factory specifications. All of the parts – block, crankcase, head, transmission housing, etc. – must be inspected for cracks or other damage. All moving parts – pistons, crankshaft, camshaft, oil pump, bearing and bushings, flywheel, water pump and all others – must be cleaned and measured against factory specifications and, if necessary, machined or re-manufactured to bring them within specifications. The same goes for the transmission, clutch, differential and all other moving parts of the power and drive line. The electrical system has to be inspected and, if it shows chafing, wear or damage be replaced. If the car is old enough to have used rubber or even fabric based electrical wiring insulation, this should be replaced even if looks okay and upgraded to modern insulation because it is a fire risk. Then the entire engine and driveline is reassembled, replacing all worn bearing and bushings, seals, gaskets, belts and gears.
Finally, the engine/driveline has to be re-installed in the frame, the brakes, wheels and other parts re-installed, the body fitted to the frame and the entire car rechecked and tested.
Restoration of a car is a daunting task, not one to be undertaken lightly, or by the inexperienced. A full restoration can take many years and can cost tens of thousands of dollars; often, and generally, well in excess of what the finished value of the car will be. Many jobs will have to be farmed out to specialty shops; those with the special knowledge and equipment to do the job. Often a restoration once started is left unfinished and the car and parts can be purchased for a fraction of their worth. However, if a person buys an unfinished project, it is imperative to be sure that all of the parts are there. Finding parts for an orphan or rare car can sometimes be impossible. This necessitates the fabrication of parts from scratch, generally at great effort and expense.
There are different levels of automotive repair. The highest quality level, generally unobtainable for the amateur restorer, is the Concours d'Elegance level; these are cars that are frequently restored to a degree often beyond the quality that they were when they left the factory. There are virtually no deficiencies in the quality of the parts that were actually restored. Those parts that did not come on the car as it was first sold must have the highest level of fit and finish, and appear to have been original parts. Many Concours cars are not driven except for the short distances from their trailers to the show field.
Only when a car is completely placed back into the condition it was first sold in is it considered to be restored. Various aspect of a car may be repaired without the car being restored. Automotive Restoration means that the car was put back into the condition it was first sold as. Anything else is either repair, or a restomod. Between these two extremes are the vast bulk of cars that are seen as drivers, neighborhood show cars, and 20-footers - in that they look great from 20 feet (6 m) away. Many value guides offer six levels of quality, from a "parts-only" car to the best at "Number 1" - absolutely perfect in every way.