An Amateur Mechanic's Guide to Buying Complete Car Engines

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An Amateur Mechanic's Guide to Buying Complete Car Engines

Purchasing a complete car engine for fitting into a vehicle, as an amateur, may seem a daunting task; not only in successfully buying it and taking delivery, but the challenges of fitting it into a recipient car or van, and finally getting it working, may seem almost impossible. But this need not be the case. With care and attention to seemingly trivial details, the new owner can be confident that not only does the new engine actually fit into the new vehicle, but that on turning the ignition key for the first time, the engine will fire into life.

When buying a complete car engine, it is important that a few simple steps are covered, such as knowing the engine type, model, size, and other essential pieces of know-how. Information and pointers gained by the intended amateur mechanic only increases his or her knowledge, and ensures that he or she buys the correct engine for the intended vehicle, and that the whole process is as smooth and trouble-free as possible.

Getting the Right Engine

Many car and van makers now produce several different models, often with entirely different engines for vehicles of a particular model. For example, in a particular range, the engine sizes may range from 1.1 litres, normally aspirated, up to 2.2 litres, including a turbo-charger. Fitting a 1.1 litre engine in place of a 2.2 litre may save on fuel costs, but the engine performance would be much lower. Other factors that should be considered when getting right engine include the kind of fuel used, knowing what is included with price, and extra parts which should come with it.

Petrol or Diesel Engine

Many cars and commercial vehicles now come with the option of petrol or diesel engines. It may sound completely obvious, but it is worth checking first to see that the intended new engine runs on the same fuel as the original car or van.

If the buyer is a more accomplished mechanic, and wishes to convert his or her vehicle from petrol to a more efficient diesel, then it should be noted that a completely new fuel system should be fitted, including a fuel line, a fuel filter, and a fuel tank. This is to avoid cross-contamination, which results in catastrophic failure if not dealt with. At the very least, the entire fuel system must be completely cleaned out before attempting to run a vehicle on different fuel.

What is Included in the Price of the Engine?

Many complete engines are advertised as 'straight from the donor vehicle', but it is worth checking to see just what extras are included in the price. The first and most obvious check is to see whether a gearbox is included. Failure to check may result in disappointment when the buyer realises that he or she needs a gearbox, or other essential pieces, to go with the newly acquired engine.

Parts Which Should be Included with the Engine

Also to note are items such as a water pump, a fuel pump, a steering pump for power steering, an inlet manifold and carburetors, an exhaust manifold, and possibly an alternator. If the vendor is selling the engine as 'fully complete, straight from the vehicle', then these are more likely to be included, but a check is essential.


Many reputable vendors include an indication of just how many miles the replacement engine has done in its original vehicle. Normally the higher the advertised mileage, the lower the price. Up until recently, engines which had travelled over about 100,000 miles were considered worn out and not worth the trouble to replace even older engines with, but with the recent advances in engine and materials design and manufacturing, this is no longer the case. Some modern engines, particularly diesel models, are only considered to have been 'run in' after 100,000 miles. If the purchaser is unsure, then asking the vendor a question is always advised.

Engines for Special Car Projects

Kit cars and home-built racing cars are becoming popular, and so the need to purchase engines for them has increased. Advertisers sometimes say that their engines are ideal for an enthusiast to build a kit car project, and go as far as saying which kit car their engines fit. This is useful for the potential buyer, but the buyer should always check with the manufacturer of the kit to ensure the engine will fit with little or no modification to the kit's chassis.

Upgrading an Engine

Some purchasers want to upgrade their engines to a higher capacity or to a 16-valve model, in an effort to customise their cars. Before attempting this kind of engine replacement, the buyer should be aware of certain factors involved in the uprating of an engine.

Engine Mountings

For a higher powered engine to be successfully fitted, careful attention must be paid to the engine mountings. If the user is attempting to upgrade an engine to give it more horsepower, then it is worth checking with the official manual to make sure that the engine mountings are sufficient enough to handle the extra torque generated by the new motor. If not, then additional welding may be necessary to increase their strength.

Exhaust and Inlet Manifold

Higher powered engines have additional requirements in their exhaust and inlet systems. Often, a water-cooled inlet manifold is needed, and an exhaust manifold is required to run at higher temperatures than a standard motor.

Other Upgrades Needed

If the amateur mechanic is looking to upgrade the engine in his or her vehicle to one with more horsepower, then there may be other considerations to take in, such as whether the new engine needs an oil cooler, whether a higher powered alternator is needed, and other such factors. If in doubt, the mechanic should ask people who have performed the same operation, or failing that, an Internet search is advised.

Informing the Relevant Authorities

When upgrading a car engine, at the very least, the vehicle's insurers need to be informed, and the government needs to know to be able to issue a new vehicle registration document. The new engine's unique identification number also needs to be passed on for the new document.

Replacement Engine Electrical System

Back in the 1980s and early 1990s, engine replacement was simply a matter of taking out the old one, fitting a new one, then reconnecting all the various parts to make the engine run. With the advancements in engine technology, particularly in the field of emissions control, reconnecting an engine may require painstaking and careful replacement of the many wires and sensors modern engines now have fitted as standard.

Taking Photos of the Original Engine's Electrical System

If the buyer is not completely confident in changing an engine, before removing the old one he or she should carefully note which wires go where. If the buyer has a digital camera handy, it is worth taking as many photos of the old engine before removal as possible, paying particular attention to the orientation and colourings of sensor wiring.

Additional Information About Engine Replacement

Replacing a car engine is just about the biggest job a mechanic can contemplate on a car, especially an amateur mechanic. Time spent reading through the relevant books, magazines, and websites is not time wasted. The mechanic may also consider contacting others who have done this to see if there are any tips or tricks that should be known. Many groups, both Internet and real world, exist for particular makes and models of cars and vans, so an Internet search may be in order.

How to Buy a Complete Car Engine on eBay

Buying a complete engine on eBay should be easy and painless. Simply type in the required model of car engine you wish to buy with the word "engine" afterward, and the required pages will come up. When looking for an engine, as previously stated, be sure to get the exact model you require, with the year of the recipient car or van if necessary. Check out the seller's return policy to see if he or she will accept a return in the event of a problem with the purchase.

Because a complete car engine is by its very nature a large and heavy purchase, the seller may insist that the car engine be collected by the new owner. If the seller is willing to mail the engine to the purchaser, it is then worth noting how far away from the purchaser the seller is, because shipping charges could be unexpectedly high if the seller is some distance away. If you are picking up your new car engine in person having a trailer handy may be in order.


When looking to purchase a complete car engine, it is very important that the buyer consider the exact type of engine required, even down to the year of manufacture of the original vehicle. Then the buyer should carefully read the advertisement to see what extras, if any, are included in the price of the new engine. Particular attention should be paid as to whether the seller is offering just the engine, or the complete engine and gearbox assembly. The buyer should then note the mileage of the new engine, if this is advertised. If it is not, then the seller should be more than willing to answer any questions the buyer should have about mileage.

Finally, when replacing a car or van engine, it is important to comply with the law and inform the insurers of the vehicle and the relevant government authorities with the new engine number. If the engine is being uprated, then the insurers should definitely be contacted, as this may have implications for future insurance premiums.

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