The Engine Swap Complete Guide

by | Jul 22, 2020

So right off the bat, let me be honest with you. There’s no way in hell that I’m going to be able to cover the specifics of every engine swap. There’s just too many details and you’d be here all day.

What I’m going to do instead is cover all the big questions I get asked whenever someone comes into my shop. In over 20 years as a performance mechanic, I’ve seen some incredible swaps.

And then I’ve seen some incredibly stupid swaps. Like a V8 in a 1998 Civic. Hey, at least it did the quarter in about 11 seconds.

It looked something like this.

So if you’re planning on doing an engine swap, or just want to find the nuts and bolts information about the engine process, we’re going to cover it all today.

Whether you want 2,200 horsepower in your daily driver, or you just want to see some awesome freaking mods, we’ll get to that.

What Is An Engine Swap?

An engine swap is the process of replacing the original engine of a car with a new engine. Engine swaps are normally performed for performance, although they are sometimes done to repair a car. I mean, did you expect something different?

When you’re swapping an engine, you’ve got two options. You can either swap another engine that’s designed to work in the car you have, or you can swap in one that’s totally different.

As you might imagine, swapping in a completely new engine is way more difficult than putting in a manufacturer approved alternate engine.

Putting in a completely different engine will require more work and money, because you’ll need to modify the recipient car to fit the engine, along with making sure that everything is hooked up correctly. It’s difficult, and it’s time-consuming. But it’s doable.

However, if you’re a first timer – be warned, it’s not easy.

Is An Engine Swap Hard?

A new engine in a used car. What could possibly go wrong?

Well, as it turns out, quite a bit.

Often times, I’ll hear someone at my shop or the tuning forum I run that “It should just bolt right in”

Whatever that means.

Because after 20 years I don’t think I’ve once seen any engine swap go as easily as I’d hope. That’s just the nature of the beast unfortunately, and why most engine swaps are best left to the professionals.

Without any background on the subject of engine swapping, Mr “It Just Bolts In” guy usually assumes that just because a 2JZ Supra engine will bolt into a 240Z and simply work; dials, safety systems, everything, because they’re from the same manufacturer.

Credit: Motor1

But…it doesn’t work like that. Is anything in life as easy as it seems?

Engine swaps aren’t as simple as taking one engine out and putting another one in. Far from it.

In reality, engine swapping is a lengthy process requiring lots of research & planning, along with an exceptional amount of time under the hood, plus solid fabrication skills, and that’s just to get the engine mounted correctly so that it doesn’t decide to fall out while you’re driving.

Once it’s mounted, the work has only just begun. Then you need to make sure the engine’s power is actually being transfered to the wheels which can sometimes mean heavy modifications to your transmission.

Don’t forget, you also need to get air and coolant into the engine to the point where the air flows in, and the coolant fills around the engine, and back to the radiator again.

Oh wait! This new engine also has to send electronic signals to the dash, which means it also needs to be wired correctly. Plus, if you get this wrong, your gas pedal may decide to take a day off.

And if I’m being honest, I’ve never seen someone correctly wire a replacement engine the first time around. Shit, the first time I tried it, I ended up screwing up my project car so badly it sat in my garage for 4 months before I had the heart to get back to work.

If you’re new and feeling up to the challenge, you may want to watch this video below.

Yeah I know, it’s not exactly an encouraging take. But that’s the truth. Getting an engine swap right the first time is hard. Ironing out all the issues isn’t a one time thing. It takes a process of trial and error over many months. I’ve seen guys spend thousands trying to get their new engines to work perfectly, only to end up stranded on the side of the road for the fourth time since the engine was replaced.

That doesn’t mean you can’t do it though, it just means you need to be strategic about the type of engine swap you do.

Find a common engine swap that has been done before, and ideally already has a complete kit avaible. You’ll have a much easier time if you follow the path someone else has already blazed.

That said, if someone asked me how hard is it to swap an engine, I’d give it a 10/10 on the difficulty scale, even with a kit. There’s just so much that can go wrong if you’re not careful.

Can You Swap A Gas Engine To Diesel?

A lot of times when someone asks me if they can do an engine swap, it’s from a gas engine to a diesel.

The answer is yes, you certainly can. And yes, it’s pretty freaking impressing when you cram a Cummings into a Super Duty.

But, there are a few things you need to consider.

Running a diesel engine is going to require some work, make no mistake. And unless the vehicle you want to swap was originally intended to have a diesel engine, you’ll need to be careful.

You’ll need to think about things like:

  • Engine weight: Diesel engines are heavy. How do you plan to keep structural integrity?
  • Engine dimensions: Is the engine going to fit in the bay? Will you need a scoop?
  • Transmission & Rear Axle: If you plan on going up in horsepower, ou’re probably going to need to address the axle, as it won’t survive the torque of a more powerful engine. Same goes for the transmission.
  • Electronics: If you’re rolling with a mechanical engine, you’re good here. Otherwise, any electronically controlled diesel engine will need to be able to speak to the transmission. It helps to have a donor vehicle here.
  • Emissions: Swapping a diesel make require your car to undergo additional inspection requirements in the state you live in. See our post about Emissions Laws and Emission Inspection Requirements By State.

But, on the other hand, a diesel swap does have the potential to significantly boost your fuel economy, and increase the power of your ride.

But, in order to get to that point you’re going to have to spend.

Which leads us to…

The Pros & Cons Of Engine Swapping

There are some major benefits to swapping in a new engine, but there are also some major downsides as well. I’ll cover both to give you a better idea of what to expect.

Pros:

1: More Power

If you’re doing a swap for non-maintenance reasons, you’re probably looking to upgrade your car. With an engine swap, the only limit is how much you can manage to cram under the hood.

2: Easier To Mod/Find Parts

Some stock engines don’t have a deep selection of aftermarket parts, so you may want to swap in another engine that has a wider selection of aftermarket parts. This is also true if your car has an old engine that is difficult to find parts for.

3: Can Save Money (Maybe)

Engine replacements are EXPENSIVE. We’ll explore just how expensive in a bit. However, even though they are expensive, swapping out an engine is still cheaper than buying most used cars.

4: More Reliable (Maybe)

All else equal, swapping in an engine with fewer miles does mean that in theory, your engine should be more reliable. However, with any kind of huge mod like this, there’s an asterisk. It depends on what engine you decide to put into your modded car.

I’ve seen many guys I know get burned by used engines with supposedly low miles, especially when it comes to compression issues.

Cons:

1: Expensive!

As a young mechanic, I’ll always remember something one of my mentors told me. He said “whenever you’re doing an engine swap, take your expected budget and multiple it by 3, and then you might not go over budget”.

Yeah. He was right.

We’ll get into the specifics of price in a bit, but at a minimum, you should expect to pay at least $3,000 dollars for an engine swap if you’re paying a mechanic to get it done. If you’re doing it yourself? You might not pay as much in cash, but you sure will pay in labor.

And that’s not even considering the other things swapping your engine may force you to replace. See 3.

2: Takes Time (And Then Some)

If you’re doing a vis a vis engine swap, the entire process will probably take you a minimum of 4-6 hours of work to get the engine out and then to get another 1-2 hours double-checking once the new engine is in.

And that’s if you’re good at wiring. If you’re not, you need to find someone who is, because I promise you, the wiring is what will kill you.

Again, this is an assumption, and it assumes you’ve had experience tinkering on the car you’re doing the swap on. Because if not, it can take much longer. If you’re installing a completely different engine, your recipient car may need more modifications that take time.

Unless you’re one of those guys that likes having his project car always in the garage, that’s not ideal. Especially if you need to put in a new transmission.

3: You May Need To Change The Transmission

Depending on which engine you decide to swap into the vehicle, you may need to change the transmission. Generally speaking, the more different the engine is that you are putting in, the higher the chance you’ll need to swap the transmission.

A good example of this would be a GM LS swap into pretty much any smaller RWD car (ie 240SX, Miata, S2000, RX7, etc). None of these transmissions will bolt directly to the GM LS engine.

And none would likely survive the HP and torque of the GM LS. This would preclude simply using an adaptor plate or custom bellhousing on the original transmission.

Of course, when the swapped engine is similar to the original engine, it is often compatible with the original transmission. A good example here is the swap of a Toyota 3RZ into an older 22RE equipped truck. Because the engines are so similar, the 22RE transmission will bolt straight up to the 3RZ. 

4: You May Need To Re-Register Your Vehicle

Depending on the jurastiction you live in, swapping in a new engine may require you to re-register your vehicle. This is especially true if the vehicle was formerly titled salvage, or you’re looking to get a rebuilt title.

Make sure you check with your local DMV for more information on if you need to re-register or not.

5: Emissions Concerns

When you put a new engine in, you may also have to undergo emissions inspections. We’ve previously done an article on the inspection laws in each state, so check there for more information on what you need to do.

How Much Does An Engine Swap Cost?

As previously mentioned, when someone asks “how much is an engine swap”, there’s never one answer. Again, it all depends.

If you’re taking it to the mechanic to be done with a common, mass-produced engine, you’re probably looking at somewhere between $3,000-$5,000 dollars for the entire job, including a used engine.

Doing it yourself however, is a bit more complicated. There are so many different permutations that your cost could be anywhere from $0 (if you somehow have an extra engine laying around) to over $10,000, easily.

So instead of throwing out a number like $7,000 or something like that with no context, I’m going to break down the factors that will increase your cost so you can begin pricing out the job yourself.

Sound fair?

1: Your Choice Of Engine (Very Important)

By far, this is the most important choice you’re going to make while doing your engine swap. The type of engine you choose will set the price for the rest of the build. Choose an engine that actually bolts right in, and you’re going to save yourself a lot of work, and a lot of money.

The quality of the engine also matters. For example, you might be able to steal an EJ255 2.-5 liter turbocharged flat-4 from an old Subaru Forester for $200, but if you opt for something more expensive like the Blueprint Engines 347CI Stoker Crate Engine, you’ll be looking at a bill of $5,100.

There are also plenty of high power options that run well over $12,500, so again, the actual engine price is really going to be up to you.

Reasonable Cost Estimate: Between $400-$7,000

2: Your Choice Of Transmission, If Applicable (Very Important)

Depending on your choice of engine, if you’re lucky, you won’t have to replace the transmission.

Obviously, that will save us quite a bit of money.

And again, your choice of transmission matters. You might be able to get one for next to nothing from the junkyard, but there’s always the option to buy a stock transmission for between $1,000 to $2,000.

On the other hand, if you want to go with something a bit more upmarket, like a American Powertrain Tremec T-56 Magnum Manual 6 speed transmission, be prepared to pony up the cash, because you can expect to pay upwards of $3,250.

Granted, if you’re going to upgrade your engine, you probably want to have a manual anyway, right?

Reasonable Cost Estimate: Between $250-$3,000

3: If You Use A Swap Kit or Junkyard Parts (Important)

Repeat after me: It will use the swap kit. Otherwise it will go back into the garage.

Seriously. I helped my neighbor swap the old 1.6 in his Miata for a 1.8. We used a swap kit, and between the two of us we got it done in a weekend.

On the other hand, my first swap about 20 years ago took me over 6 months to finish. Everything went wrong, all the way from the fuel pump to the damn mounts.

For anyone thinking about doing an engine swap for the first time, if you ignore everything else I say except for this, your time will still have been worth it. If you can use a swap kit, use it.

Ideally you will have picked an engine to swap that you know already has a swap kit. Using a swap kit means you won’t need to do much (if any) custom fabrication, which not only will save you a shitload of time, but will make the entire process way less stressful.

Depending on where you order your engine from, it may actually come with a swap kit. The swap kit you get depends on the engine you’re installing. Some kits are cheap, and start at only $500 dollars, while others are upwards of $6,000. Again, it really depends on your engine.

Is it cheaper to get parts from the junkyard? Yep. But those savings come with a cost: time, You’re going to spend more time searching for the right parts, or fabricating them.

You’re paying for the convience here – and the knowlege that your swap will be done right.

If you choose to get parts from the junkyard, you’re going to be working.

Seriously, get the swap kit. You’ll thank me later when your beautiful 3.0T doesn’t fall out at 80 miles per hour.

Reasonable Cost Estimate: $100 – $5,000

4: The Tools You Need (Important)

If you’re serious about doing an engine swap, I’m going to assume you have all the tools. If you don’t? I hope you’re not planning on doing anything more than a true vis a vis swap where you literally just bolt the new engine in.

Otherwise, you’re going to have a rough time.

Reasonable Cost Estimate: Hopefully you have them, or have a 6 pack of beer you can lend to your buddy to borrow his.

5: Everything Else (Important)

Assuming you’re doing a more complicated swap, an engine kit is only going to get the drivetrain handled. The truth is, engine swaps are expensive because of what it means for the rest of the car.

Keep in mind you are changing the WHOLE drivetrain, you aren’t just taking a motor out and putting a new one in. Everything that the drivetrain touches or interacts with will need to be looked at. You could need anything from: New fuel pump (which may mean new fuel pump wiring because the stock wiring can’t handle lots of amps), new fuel tank venting system, fuel regulator, potentially AN lines, new exhaust, new exhaust hangers (because potentially dual exhaust with V8), there is so much to consider.

Also keep in mind that’s it’s never worth half-assing a swap.

If you are going to spend a year and $10,000 to make 300whp, it’s most likely worth it to bump up a few grand to make 400whp. For example I was originally planning to use shorty headers on my LS1 (~$250) but I thought I may eventually want long tubes if I decide to bump up power in the future.

Remaking the exhaust would suck after the fact, so I sprung for the V8roadsters long tubes (~$1000).

The cost at this point really depends on you, and unfortunately this makes it hard to nail down a price here.

Reasonable Price Estimate: $0 – $6,000+

Total (Reasonable) Cost For An Engine Swap: $750 – $20,000+

As you can see, that’s a pretty big range, because there are so many variables involved here. The good news is, I do actually have an answer to the question though.

Most guys I know that do engine swaps spend between $2,000 – $8,000 or so. In my opinion, this is what you should plan on budgetting if you’re doing a first time engine swap.

As a rule of thumb, the simpler the engine swap is going to be, the less it’s going to cost.

How Much is Labor For An Engine Swap?

Credit: Je Import Performance

A standard engine swap takes between 15-20 billable hours. The average US mechanic labor rate is $100/hour. You should expect to pay between $1,500 to $2,000 for labor during your engine swap.

How Long Does It Take To Swap An Engine?

Want to hear a joke?

Swapping your engine is time consuming! Now where have you heard that before?

Hmm.

To answer this question, I’m actually going to give you two answers. I’m going to give you the one you’re looking for, and the one you actually need.

If you’re just swapping the engine out and it literally bolts right in, you can expect to get the job done in a weekend. If you’re good, you can do it in somewhere between 5-8 hours of work.

You can expect about the same thing (2-3 days) if you’re taking your car to a mechanic for a regular engine swap for maintenance.

But, if it doesn’t just bolt right in (and let’s be honest guys, it never really does) you’re looking at a much longer and more involved job.

In my mind, there are really 3 tiers of swaps.

TIER 1: Same Engine, Or Performance Version Of Your Engine

The same engine, or the performance version of the engine your car already has. Imagine plugging a WRX engine in your Impresza. Both are made by Subaru, and it essentially bolts right in.

These swaps aren’t very difficult, and you can typically knock these out over the course of a weekend. This is about the same amount of time a dealer will take with this level of project.

I’m assuming you’re at least relatively competent here for the time. Double this if you’ve never done anything like swapping an engine before.

Estimated Labor Time: 4-12 hours

TIER 2: Not The Same Engine, But Well Doccumented & Supported

Well doccumented swaps that have already been done multiple times, and have swap kits avaible. These can still be a pain in the ass, but are more accessible than true custom swaps. A common example of this is putting an LS1 into a Miata.

If you have everything you need, which includes the tools and parts, this swap will take about 25-35 hours of hard work. However, it can take longer.

Nathan Sumner, who wrote about his experience here, had his LS1 swap take almost 200 hours, although it was while he was in school, so take that with a grain of salt.

The time it takes you to complete a more well doccumented swap really depends on your level of organization going into the project, as well as the quality of the doccumentation you’re using.

Estimated Swap Time: 40-80 hours

TIER 3: Completely New Ground

A completely new swap, that either hasn’t been done before, or has very limited documentation.

These swaps seperate the men from the boys and require a huge amount of custom fabrication that put them beyond the reach of most of us reading this article (including me).

Putting an SR20 in a Miata is just one example.

A friend of mine managed to swap an SR20 into his 91′ Miata. Guess how long it took him? Not 1 year. Not 2.

It took him 12 years. Of course, with his wife and kids he only had time to hit the garage on weekends, but this should tell you how difficult the swap was. In his own words:

I wouldn’t recommend this conversion to anyone. It looked like everything was going to fit at first. But then it didn’t. And that’s where the problems started

James F – DelRay Beach, Florida

Estimated Swap Time: 100-200+ hours or more, depending on your level of experience and creativity.

Again, the length of time your swap takes you will vary. You can expect that the length of time will scale when you have less experience, or if it’s a less doccumented job.

So, Is An Engine Swap Really Worth It? Ask Yourself These 4 Questions First.

In my opinion, if you are asking yourself this question, there are really three things you need to consider.

Again, these are 4 things I would consider. You need to do your due dilligence as well.

1: Is Your Car Running?

The first thing you need to ask yourself is if your car is running correctly as it is.

If it’s not, by all means, make the swap.

But if it’s running good as it is, you need to be prepared for the possibility that swapping the engine will cause something to go wrong.

Again, it depends on the build you’re going for. A more complicated build has a greater chance of something going wrong. Which leads us to your next consideration

2: Is It Your Daily Driver?

If it’s your daily driver and you need a maintaince related swap, unless you know what you’re doing it’s better that you take the car to a professional.

In my opinion, you should never do more than a Tier 1 swap with any car you rely on. A tier 1 swap is a swap that can easily be completed in a weekend.

It’s a true “bolt in” job.

Because things always go wrong with engine swaps. It might be something minor, like forgetting to clip a wireing harness in, but when it’s not…

You would think this is common sense.

You would think.

If the car you plan on swapping the engine into isn’t your daily driver, you have room for shit to hit the fan.

And assuming our next consideration falls into place – if it’s not your daily driver – you’ll have lots of room to screw things up and make upgrades, because let’s be honest, there’s always a part that’s just a bit better.

3: Do You Have The Time/Money?

Unless it’s a simple build, you’re going to be spending some cash.

Nate Sumner, who we talked about before did a Tier 2 swap with an LS1 into his Miata. That build cost him almost $10,000 dollars and nearly 200 hours of his time.

Of couse, you can get a build done with less time and less money. But there may be tradeoffs, from what parts you use, to the amount of end power you get.

Which leads us to our last consideration.

4: Is The Build Worth The Tradeoffs?

If you’re serious about this, the last question you need to ask yourself is if you’re really prepared to accept the potential costs. If you have plenty of time and money, and you’re just tinkering with your second car, by all means, it’s probably worth it.

On the other hand, if it’s your daily driver for work and to pick up the kids, you probably don’t want to go for something above a Tier 1 swap.

Again, everyone has a different situation. You have to figure out if it works for your situation.

Because when it does, the results are freaking sweet.

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