Swapping a 2.5-liter Into an NC Chassis MX-5

There are lots of resources on the web about what it takes to perform a 2.5 swap in an NC chassis MX-5, and even though I have read as many of them as I could find, I still wasn’t quite sure what I was getting myself into.

It all started with buying a 2006 MX-5 from Copart that I hadn’t seen in person. The photos weren’t too bad and the website said it ran and drove, so I pulled the trigger. The website did not say it had a tire with a screw in it or that it had a worrying top-end clatter. I also had no way of knowing it would develop a misfire within days of getting it back on the road.

It was then I started looking into a 2.5 swap. Engines were cheap and plentiful through the online salvage parts site LKQ. I found a 19,000-mile engine out of a T-boned 2017 Ford Fusion for around $750. A 2.5 engine costs more when you get it out of a Mazda for some reason, even though they both have FoMoCo cast into the side of the block.

Before you can begin to think about pulling the engine, there are a lot of things that have to come out first, including the battery, coolant expansion tank, power steering reservoir and cooler and the airbox. Then, of course, there’s a lot of wiring connections. There isn’t room to detail all of what it takes, but if you’ve pulled engines from other modern cars before, you have what it takes to do it on an NC.

The first thing to consider when pulling an engine out of an NC chassis is that the only way they come out the top is if you separate the engine from the transmission. That sounded like more work, so it was going to have to come out the bottom. If you don’t have a lift, you’ll have to put the car on jack stands on one of their higher settings so you can lower the engine and suspension out the bottom.

That requires removing or disconnecting the front suspension and disconnecting the brake hoses and the starter, steering column shaft and the cooling system and the clutch hydraulics. This car is getting new-to-me shocks and springs and new stainless-steel braided brake hoses, so I removed them rather than just disconnecting them.

To disconnect the shocks, it’s similar to an NB. Remove the sway bar link so you can get lots of droop. Then remove the two bolts on the upper control arms so you can pull the shock out from inside it. It’s similar to the long-bolt procedure on previous generation Miatas.

The first things to remove are the hood, front fascia, wiper cowl trim and the steel access panel in the middle of the firewall behind the engine. Those are all simple jobs, but they do take some time. Based on past engine jobs I’ve done on the NB chassis, I thought I’d be able to take the air-conditioning compressor off the block and hang it off the chassis with mechanic’s wire, but that doesn’t work.

If you remove an engine from a NC with air conditioning, the better way to go is to have the refrigerant evacuated first so you can remove the hoses from the compressor without getting oily lime-green R134 refrigerant all over everything. That also will allow you to remove the radiator and A/C condenser as one assembly. The way I did it, leaving the condenser in place while removing the radiator also wasn’t the right way. They’re bolted together with lots of brackets and lines so pulling them as one piece is easier.

You’ll want to drain the engine oil and coolant, but a lot of coolant is going to spill during the job anyway. You’ll also want to remove the battery, coolant expansion tank, power steering reservoir and cooler and the factory airbox.

Because the transmission is coming out with it, you also have to drain it first, then remove the shifter knob and the center console. When you get the console out, you can remove the shifter along with the upper and lower shift boots, which likely will need to be replaced. After that, duck underneath the car to remove the driveshaft and power plant frame, and disconnect the four blade-terminal connectors. Disconnect the slave cylinder hydraulics from the top left side of the engine. All this transmission work is similar to NA and NB chassis Miatas.

I had never dropped an engine out the bottom in my garage before. I had seen it done many times with the aid of a lift when I worked in a Pontiac dealership many years ago. Doing the job with jack stands, an engine hoist and furniture dollies from Harbor Freight is another matter altogether.

The idea was to set the jack stands as high as I was comfortable with, then lower the front suspension cradle, engine and transmission onto furniture dollies and roll the whole assembly out from under the car. If I needed to lift the car more to get the engine out from under it, I could use the hoist to lift the front of the car.

Turns out I wouldn’t need the hoist. With no engine or suspension in the car, two guys were able to pick up the front the car while another set the jack stands higher. The engine and suspension rolled out from under the car.

Once you get the engine out, that’s when you can separate it from the transmission and get it up on an engine stand to begin all the steps to swapping necessary parts from the original 2.0-liter to new 2.5-liter. This part of the story focuses on getting everything out and on a stand so you can work on it. For this job, you need two engine stands, one for the old engine and one for the new one.

The next installment in Speed News will be the detailed processes of the 2.5 swap. Then we’ll show you what it takes to set the timing in a 2.5 MZR — it’s not like anything I’ve ever seen — and getting it back in the car and running again.