When your engine starts to show signs of wear such as burning oil, losing compression, or declining performance, you may be faced with the decision of whether to rebuild or replace it. There are pros and cons to each option in terms of cost, longevity, and other factors. Here’s an in-depth look at the rebuild vs replace dilemma.
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What is an engine rebuild?
An engine rebuild involves removing the engine from the vehicle, disassembling it, cleaning and inspecting all parts, replacing any damaged or worn components, and reassembling the engine with all new gaskets, seals, bearings, and other parts as needed. The block, heads, crankshaft, and other major components are reused if they are in good shape. The goal is to restore the engine to like-new condition and achieve close to the original factory specifications for performance and longevity.
Reasons to rebuild an engine
There are several reasons you may want to consider rebuilding an engine:
- Cost – In many cases, a rebuild is cheaper than replacing with a remanufactured or crate engine.
- Familiarity – You know the history and condition of the original engine, unlike a replacement.
- Retain original engine – Keeping the original engine preserves the authenticity and collectibility of a classic or antique vehicle.
- Higher rebuildability – Some engines have a reputation for being easily rebuilt to like-new condition.
- Availability – The specific engine may no longer be in production so a replacement is hard to find.
Reasons to replace an engine
There are also solid reasons you may want to opt for a full engine replacement:
- Cost – In some cases, a remanufactured or crate engine can be cheaper than a rebuild.
- Convenience – You can have a replacement engine installed much faster than doing a rebuild.
- Reliability – A factory reman or crate engine comes with a warranty, unlike a rebuild.
- Performance – Upgrading to a larger displacement or higher tech engine can give big power gains.
- Damaged block or heads – Extensive damage may make the original engine unrebuildable.
Cost comparison
One of the most important factors to weigh is the cost difference between rebuilding or replacing your engine. Here is a general comparison of price ranges:
| Option | Typical Cost Range |
|---|---|
| Engine Rebuild (parts and labor) | $2,000 – $4,000 |
| Remanufactured Engine | $3,000 – $6,000 |
| Crate Engine | $4,000 – $8,000 |
These are just general estimates – actual costs can vary considerably depending on engine type, who does the work, and other factors. But it gives you an idea of the typical ranges.
Key cost variables
Some of the key variables that affect the cost difference include:
- How extensive the rebuild needs to be – Full teardown and replacement of all major components is more costly than a basic rebuild.
- Level of craftsmanship – A premium rebuild done to concours standards will cost more than an economical “pump and dump” rebuild.
- Cost of individual parts – This can vary widely depending on brand, reusability of original parts, and production status of the engine.
- Machine work needed – Boring/honing cylinders, crankshaft grinding, etc adds expense.
- Labor rate for installation – Dealers tend to charge considerably more than independent shops.
Longevity
The expected longevity of a rebuilt engine versus a replacement engine is another key consideration.
Rebuilt engine longevity
How long a properly rebuilt engine will last depends on factors including:
- Quality of the rebuild – Cutting corners reduces lifespan.
- Level of use and maintenance – High mileage or neglect shortens engine life.
- Type of engine – Durable designs like an old Chevy small block can easily get 100k+ miles rebuilt.
- Usage – Heavy load applications shorten the lifespan.
- Quality of replacement parts – Aftermarket and OEM parts vary widely in durability.
Under ideal conditions – a meticulous rebuild using all top quality parts and well maintained – it’s not unusual for a rebuilt engine to deliver 100,000 miles or more of reliable service. But a budget rebuild with off-brand parts might start burning oil or losing power in half that mileage.
Replacement engine longevity
Replacement remanufactured or crate engines also have quite variable lifespans:
- Quality – Premium remans made by OEM suppliers often match factory engine life. Budget no-name remans don’t last as long.
- Warranty – Most crate engines come with 1-3 year unlimited mileage warranties for peace of mind.
- Miles on engine – Remans with only 30-50k miles tend to last longer than those with 80k+ miles.
- Maintenance – Poor maintenance shortens any engine’s lifespan.
The highest quality reman or crate engines these days are on par with or even better than the original factory engines. But lower cost replacements don’t always live up to the longevity claims.
Performance
Engine performance is another consideration when deciding whether to rebuild or replace. There are a few key factors to keep in mind:
Rebuilt engine performance
- A proper rebuild restores performance close to original spec, though rarely exceeds it.
- Upgraded internals like forged pistons/rods, performance cams/heads, or forced induction can increase power output of a rebuilt engine.
- High mileage engines may lose some performance from worn-out components.
- Neglecting proper machine work and assembly techniques results in poor performance.
Replacement engine performance
- Factory reman engines match original output.
- Crate engine upgrades (stroker kits, high flowing heads, etc) offer big power gains.
- Swapping to a larger displacement engine greatly improves performance.
- Forced induction engines (turbos/superchargers) make huge power but strain drivetrain.
Either rebuild or replacement offer potential for increased performance. But replacement makes upgrading displacement or adding boost easier. However, availability and cost may limit replacement options for vintage engines.
Reliability
Engine reliability is critical. A failure can leave you stranded and lead to major repairs. Important reliability factors include:
Rebuilt engine reliability
- Quality of machining and parts used greatly impact reliability.
- Poor assembly or improper clearances can cause failures.
- Unseen wear in reused parts like crankshaft and heads risk failure down the road.
- Reputable rebuilder using proven techniques provides most reliability.
Replacement engine reliability
- Factory remans with new parts and warranties offer the most reliability.
- Crate engines are factory-fresh but limited testing risks unforeseen issues.
- Cheaper no-name replacements often cut corners impairing longevity.
- Used engines have unknown history and abuse that affects reliability.
A quality rebuild in the hands of an experienced rebuilder can match factory reliability. But replacement engines offer a bit more peace of mind.
Availability
The availability of suitable replacement engines also needs to be factored in when deciding whether to rebuild or replace an engine. There are usually plenty of options for popular engines, but older or obscure engines can be hard to source replacements for.
Popular engine replacements
For common engines found in many different models over the years, quality replacement options are abundant:
- Small block Chevy V8 – The most popular swap engine, easily sourced from GM, crate engine suppliers, and wrecking yards.
- Ford 302 V8 – Millions built over decades means lots of choices for replacement blocks and parts.
- Chevy LS V8 family – GM crate engines and remans cover the wide range of LS engine variants.
- Modern inline-4 – Toyota, Honda, Ford, etc. Inline-4 engines used extensively, making replacements easy to find.
Harder to find replacements
On the other hand, with limited production engines, replacements can be difficult or impossible to come by:
- Old school V8s – Big block Mopars, Y-block Fords, etc. Simply aren’t many left out there.
- Obscure imports – Good luck finding a fresh Datsun Z engine, Subaru turbo EJ, or other rare engines.
- Vintage flatheads – Few repop options exist for classic flathead V8s and straight 8s.
- No longer in production – AMC, Isuzu, International Harvester engines haven’t been made for decades.
In cases like these where replacements aren’t readily available, rebuilding the engine may be the only option to keep the vehicle on the road.
Emissions compliance
Finally, consider emissions compliance when weighing your engine options. This primarily applies to newer vehicles:
- Replacement engines must meet emissions regulations for the model year vehicle or usage restrictions apply in some states.
- Exempt pre-OBD2 vehicles can legally install any replacement engine.
- Modifying engines for performance risks violating emissions laws.
- Diesel regulations are the most strict for replacement engines to meet.
- If engine swapping a newer car, ensure the donor engine is emissions certified.
For older exempt vehicles this isn’t an issue. But emissions compliance should be researched thoroughly before buying any replacement engine for a 1996 or newer model year vehicle.
Conclusion
So should you rebuild or replace your worn out engine? There’s no definitive answer that applies in every scenario. But by carefully weighing the cost, longevity, performance, reliability, availability, and emissions compliance factors, you can make the best decision for your specific vehicle and situation.
For very rare engines where replacements aren’t obtainable, a rebuild may be the only choice. And for some enthusiasts doing a ground-up restoration, preserving the original engine is a priority that justifies a costly rebuild. But in many cases, replacement remanufactured or crate engines offer comparable or even superior longevity, performance, and reliability at a competitive price point. And improving emissions, drivability, and fuel economy through engine swaps is more feasible than ever thanks to the wide range of turnkey replacement engines on the market today.
In the end it comes down to your vehicle, application, budget, and goals when choosing between engine rebuild and replacement. Carefully weighing the pros and cons of each option will lead you to the right decision.