Rebuilding an Engine: Purpose, Benefits, and Cost

An engine rebuild involves disassembling, inspecting, and cleaning the engine. All its faulty components will also be either repaired or replaced. Rebuilding an engine is an extremely labor-intensive task that requires a lot of experience and knowledge.

When Do You Need an Engine Rebuild?

An engine typically needs to be rebuilt when it is worn to the point of using oil or making noise, has major damage, such as when it overheats or if a component like the pistons, bearings, or head gasket becomes faulty.

People who have major engine issues face a choice between rebuilding their engine or replacing it completely. Most of the time, the mechanic’s recommendation will depend on the severity of the issue. If there are loud noises coming from your engine and oil is leaking everywhere, then there might be too many issues inside the engine for a rebuild to be worth it. In these cases, replacing the engine might be the better option.

Pro Tips are nuggets of information direct from ASE-certified automobile technicians working with CarParts.com, which may include unique, personal insights based on their years of experience working in the automotive industry. These can help you make more informed decisions about your car.

Pro Tip: Most shops might repair engines (including the head gasket and other parts) but will replace the engine rather than rebuild it entirely because replacement engines come with a warranty that reduces the shop’s liability.

Engine rebuilds are also typically done to vintage or classic cars that have been left unused for years. These vehicles will typically have seized engines since oil turns into sludge if an engine is unused.

Race car engines need engine rebuilds more frequently. NASCAR engines need to be rebuilt after every race. This is also done as preventive maintenance. Given the amount of stress and wear that an engine experiences in a race, engine rebuilds allow teams to make sure there aren’t any hidden issues that can affect the next race. If you think that’s excessive, top-fuel dragsters need to have an engine rebuild after every quarter-mile run. A bit of trivia: One top fuel dragster engine has as much horsepower as eight NASCAR engines.

How Long Does It Take to Rebuild an Engine?

Depending on the parts needed, rebuilding an engine can take many weeks, if not months for a DIY person that hasn’t done it before.

Sometimes, you might discover broken parts during the rebuild process. If you’re not really familiar with how to recognize parts that have failed, you might miss something like a cracked piston or a stuck oil pressure relief valve.

Pro Tips are nuggets of information direct from ASE-certified automobile technicians working with CarParts.com, which may include unique, personal insights based on their years of experience working in the automotive industry. These can help you make more informed decisions about your car.

Pro Tip: If the engine starved for oil or overheated, you need to find out why. You don’t want to rebuild an engine only for it to destroy itself again because of a bad electric cooling fan.

You’ll need to order replacement parts and this can take time. Sometimes you might find that you need parts you didn’t know about when you began. The clearance between the parts like the cylinder heads is also checked to ensure they’re within tight tolerances. This work demands a high level of skill and precision. That’s why engine rebuilding can’t be rushed.

You also need to have a good machine shop nearby, because high mileage engine blocks typically need to be bored out .030 inch and have all the pistons replaced with new ones. This is because the cylinders on high mileage engines are typically tapered and egg-shaped. Putting new rings into cylinders that are out-of-round will cause the engine to burn oil just about every time.

What Do You Need to Rebuild an Engine?

First: you need gumption to rebuild an engine. The task is complex enough that if you don’t feel you’re not completely up to it, you should hire somebody to do the job.

Next, to be able to rebuild an engine, you’ll need to have an array of equipment. These include a hoist to lift the engine out of the engine bay. You’ll also need wrenches, jacks, buckets for oil, and some space to place the disassembled parts. A head gasket and an engine seal kit is also necessary since you’ll need to replace all the seals. You’ll also need your vehicle manufacturer’s engine repair manual, which can be available online or at an auto shop. This manual will inform you about the proper repair procedures for the engine you’re rebuilding.

Experienced engine rebuilders will order entire engine overhaul kits and a crankshaft kit that comes with bearings. They’ll have the block cleaned in a vat, and a valve job done on the heads, which are also checked for cracks and flatness. They’ll have the cylinders bored out so they can use slightly oversized pistons. Overhaul kits will include all gaskets, timing components, lifters, a new oil pump and water pump, all the rubber seals and valve stem seals.

Experienced engine rebuilders will order entire engine overhaul kits and a crankshaft kit that comes with bearings. They’ll have the block cleaned in a vat, and a valve job done on the heads, which are also checked for cracks and flatness. They’ll have the cylinders bored out so they can use slightly oversized pistons. Overhaul kits will include all gaskets, timing components, lifters, a new oil pump and water pump, all the rubber seals and valve stem seals.

–Richard McCuistian, ASE Certified Master Automobile Technician

Rebuilding an engine requires a keen eye for detail as well as a strong ability to follow instructions. The individual tasks may not be that difficult to experienced DIYers, but they require precision and accuracy. Every component in your engine must be perfectly aligned with the others. The clearances between parts must be within specifications.

How Much Does It Cost to Rebuild an Engine?

Given the labor-intensive nature of an engine rebuild, having a shop do it for you will be expensive. Rebuilding an engine can cost around $2,500 to $4,000, but this will still depend on the complexity of your engine, the necessary parts, and the cost of labor. Doing an engine rebuild without the help of a mechanic is possible, but it will be a tough task.

If you aren’t confident in your DIY skills, then it’s best to leave the task to a professional. You can also buy a used engine from a reputable parts recycler or salvage yard if you think you can do a whole swap.