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5 Things To Know Before LS Engine Swapping A RX-7

Red Mazda RX-7 FD3S with modified Chevrolet LSX engine in The Elite showcase

Engine swapping is no simple feat, especially for people that haven’t done anything quite like it. There are a handful of things that you should consider before taking on such a big project yourself or spending the money to pay someone else to do it for you.

As you read through, you’ll see five things that will help you decide if LS engine swapping is right for you and some things you need to consider.

Things To Know Before LS Engine Swapping An RX-7

Swapping an engine is no small feat that can be done in a few hours. It’s a time-consuming process that will likely take two days at a minimum. However, that isn’t the only thing you need to think about when you are considering changing your Mazda RX-7 rotary engine over to an LS engine:

  • LS engine VS original Rotary Engine
  • Easy maintenance
  • Be prepared
  • Cost considerations

As you can see, there are a few things to know before you go all in on swapping the engine out. You may come to realize this isn’t the correct choice for you, or perhaps you will love the idea even more. As you read through everything here, you should have a better idea of what it is you want to do and if you have the means to achieve it.

1. LS Engine Over a Rotary Engine

Rotary engines haven’t been mass-produced since 2012. With car advancements today, we may never see these engines produced again. This may make it difficult to find parts in the future, relying on specialty shops in order to fix it. This makes the idea of engine swapping much more appealing.

Not only will parts become difficult to obtain, but the cost will reflect that. LS engines are a lot more common and are one of the most popular engines to swap to. You may like the Mazda RX-7 and the engine inside of it, but swapping the engine isn’t going to make it less of a good car, in fact, a lot of people find it to be better overall.

Rotary engines are unfortunately becoming a thing of the past. Even though they are high-revving powerful engines the LS engine can compete, especially the V8 varieties. If they were still actively produced the rotary engines would be something to hold on to, but over time it’s just going to become a money sink. Not only that, but with the rise of electric vehicles, it just won’t be worth it unless you have the funds for it.

Keep in mind that while you may love the engine swap, there are purists out there that will have an issue with putting an LS in a car that came with a rotary engine. It’s your car and you can do whatever you’d like with it, but when showing it off just be prepared for rude or snarky comments. Some people think rotary engines should stay in the cars they were designed for.

There are a lot of pros and cons to each engine type, but honestly, the LS engines are newer and overall just easier to deal with or modify. The parts will be significantly cheaper as well if something happens to go wrong and something needs to be fixed or repaired. You’ll still have a powerful vehicle, it’ll just have some different hardware than what it originally came with.

Close up of the Mazda RX-7 13B-REW Wankel Engine Motor
Mazda RX-7 FD with the original 13B-REW Wankel Rotary Engine

2. LS Engines are Easy to Maintain

Lots of mechanics out there will tell you that the LS engine is incredibly easy to maintain and repair. If you do not have a huge amount of money set aside for car repairs, the LS engine will give you plenty of life.

Alternatively, you can use it as a good engine to work on if you are a beginner. These engines are designed in a way that makes them very easy to learn how to do repairs or maintenance on. Not only that, but the engines are so common now that you can easily find parts or people that are experts at working on them.

Now, some car enthusiasts prefer to have something unique or hard to find, but the cost can get outrageous, which is why LS swapping is a good idea. Besides, is spending a ton of money on hard-to-find parts really worth it? The more time goes on, the less you’ll be able to find specific parts and it becomes a whole thing. LS engine parts are going to be easy as cake to find.

A good thing you may be able to do is to find an LS engine from a junkyard. A lot of places only charge a few hundred for engines if you pull them yourself. Even if the engine has issues, it’s still a good deal, especially if you want to work on it yourself before putting it in your Mazda RX-7. This is an excellent idea for those looking to put in sweat equity on their vehicle.

So, the long and short of it is that LS engines are usually inexpensive, depending on your location and the condition of the engine. They also are easy to modify and can easily be found basically anywhere you live. Some of the LS engines also come with decent horsepower as well. All around, the engine is one of the best on the market.

Chevy Corvette C6 engine bay with a close up of the LS3 engine motor
LS3 Small-Block V8 Engine

3. Make Sure You are Prepared

If you are going to be doing this yourself, it’s important to make sure you know how to actually swap an engine. There are a lot of parts that need to be connected and if you don’t know how to do it, can end up being a huge headache. Before you start a build, make a list of anything you will need to buy before beginning.

Also, it’s important to remember that engine swapping can take up space. Making sure you have adequate space to work is important and preferably somewhere covered and out of the elements because you want to avoid the risk of rust or vermin such as rats infesting your vehicle. Rats or mice can chew through just about anything so be mindful of where you plan to do this.

You’ll also likely need some sort of engine lift because a fully dressed engine can weigh upwards of 400+ lbs. The block alone weighs about 120 lbs and if that doesn’t seem like a lot, lifting it up and out of the car can become a nightmare without the proper equipment.

Also, things can go wrong during an engine swap so be prepared to budget for that. Resources for how to assemble and disassemble the engines are also needed to know. The last thing you want is for something to go wrong and the project stalls because the longer you don’t work on it, the less likely it will be finished on time.

If you are going to have it professionally done, get as many quotes as possible. Some shops will charge you huge amounts of money for something that other places may do for less, depending on your location. Make sure you work it all out beforehand so there aren’t any surprise issues when it comes to how much it costs. It’s also good to get a timeline set because some places will keep putting off the work on your vehicle if you act unconcerned about the time.

Close up of a red Mazda RX-7 FD
Mazda RX-7 FD

4. It can be Expensive

As with all things involving cars, things can add up. Even if it seems relatively inexpensive at first, sometimes things can go wrong or break and end up costing you even more money. Even the most well-planned out builds/swaps can turn out to be a money pit. It’s always good to plan ahead and make sure you have something saved up for just-in-case scenarios.

Now, sometimes things will go smoothly and you won’t have to worry about that but all too often, people undertake these massive projects and will end up never finishing them because of the work and expenses it takes, especially if they are doing it themselves. With mechanics, you will also need to plan for costs to run a little high as well.

Depending on the engine, transmission, and features, a swap can cost just a couple thousand upwards of $10,000. A lot of the cost really does sit within the engine and transmission. The cost of a mechanic is also not cheap, usually ranging between $75 and $200. You need to focus on someone who is knowledgeable but isn’t going to bleed your wallet dry.

The best idea is to plan the cost ahead, get some quotes and then add a little extra on top just in case. People love their cars and it’s a shame when they sit half-finished because of time or funds. That is why it can’t be stressed enough to make sure everything is in order before you start such a large project. Any extra money can be used afterward to make your car even better.

Red Mazda RX-7 FD3S close up of the carbon fiber hood

5. It Is Time-Consuming

This one is obvious, if you aren’t hiring someone to do the LS engine swap for you, then it can take a while. For someone who is semi-experienced, it will still probably take about 15-20 hours. This again does depend on which LS engine you go for. So, just remember that this process can be done over a weekend or two if you are familiar with the ins and outs of doing an engine swap

Now on the other hand, if you are a beginner, it will probably be best to read up on how to do this and make sure you have a Youtube video or written tutorial pulled up because if something comes up that you don’t understand, its easiest to nip it in the bud as soon as possible. Youtube is probably one of the absolute best resources with tons of people recording step-by-step guides.

Make sure that you do actually have time set aside for this. A car that is being worked on can take up a lot of space and be an inconvenience to you or anyone you live with. Not only that, but it can be an issue of procrastination. If the Mazda RX-7 isn’t your main driving vehicle, then it may seem like you have all the time in the world. This can lead to your car never getting its engine swapped.

Things in life will come up and delay things that are not as important but once the procrastination starts it is a hard thing to break out of and your car can be stuck sitting there indefinitely. This is problematic if the vehicle is left in an uncovered area. Having a car sit unfinished out in the elements can come with its own set of problems that aren’t going to be fun to deal with.

If you aren’t sure you’ll have the time, you may want to consider holding off on swapping the engine or you can look into having it professionally done by someone else. If you are a beginner, think about if you are ready to commit to 25-30 hours of time to do this. Someone experienced can do it quicker, so the time is padded for that. If you are a quick learner, you may be able to do it sooner.

1993 Mazda RX-7 FD showcased at the SEMA show with the hood slightly open


The biggest takeaways from this can be boiled down to time and money. Those are something that many people are short on these days and undertaking a large project like this can cost both of those. If you aren’t certain you’ll have either, simply plan it out beforehand and get some quotes on parts and labor if you are using a mechanic.

The other important factor is knowing the engine you are swapping to. Even though you will make the purists mad for swapping a rotary engine with an LS engine, you’ll have a newer engine that will last much longer. Not only that, but you will have an easy-to-work-on engine and it’ll last you a very long time with proper upkeep and care.

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Ernest Martynyuk

An automotive enthusiast who's been tinkering with vehicles since I was 15-years old. Repairing automotive electronics has been my main job for over a decade now and have a passion for everything technical regarding cars.

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