Escort GT 1.8 L in a 91 Miata, Automatic

by Ken Bittle, Thunder Bay, Ontario Canada

In the fall of 2005 I purchased a well used/abused 91 Miata as winter project with the idea of repairing it for my wife to drive in the summer. After an eventful costly transfer home to Canada (from Phoenix) I discovered it had a broken crankshaft and needed a new engine. A bit of research on yielded a vast amount of information about interchange ability of various engines that eventually led to another eBay purchase of a 91 Escort GT 1.8 DOHC engine reported to have 53k on it. Engine cost was very reasonable at $137.50 with shipping another $135.00. That compared to costs of a used Miata 1.8 of anywhere from $800.00 to $1400.00 plus delivery. Elsewhere on this site is the comment about the hassle of converting an Escort engine to the Miata, while I agree from the point of hassle, the cost is proving to be much cheaper with the Escort. Additionally I like the challenge of the project. This article is intended to be a documentation of my experience in hopes someone else may gain from it. I have done several car rebuilds including TR3, TR6, MGB, Jaguar, and many other North American and Japanese types this being my first Miata.

Overall Advice


I strongly recommend that you photograph the donor car and donor engine before you start. Open the hood and shoot as many angles and pictures as you can. Photograph the engine you are installing in as original condition as you can even in the donor car if you have that. Speaking from my first rebuild of a TR3 this has helped me more than anything once you get to the assemble stage. (It also makes a nice scrap book if you are inclined to do that).

Zip Lock Bags

These are next to the photos in paying for themselves in a rebuild. Get the ones that have a label on the side already for identification of key bolts etc for the hood, etc etc. My personal tendency is to through everything into a box hoping to never forget but when you are finally finished and want to install the hood for a test ride it is very annoying to be searching and trying 4 lengths of bolts to find the correct ones or worse yet putting in one that is too long and having it dimple the upper surface of the hood! Alternatively put bolts back in place on the component as long as they will not get lost.

Engine Build up

My original plan was to mount the donor engine on the stand and then pull the old one and build up the old one from the old one. I found it much easier to leave the old engine in the car and take everything from it you need to for the new engine. It is a lot easier to have the engine sitting firm in the car while undoing a tight bolt than having rolling around on the floor crushing your foot! It is also smaller in size and weight when it comes to pulling out.


Proper personal protection is always essential. I do all my rebuilding in my house attached garage working around running my own business so I am not speaking of a professionally rebuilding operation.

Components you are definitely are going to need:

Car work

Donor Engine 1.8 liter

Coolant Routing

If you look on the solomiata site you will find an article about heating problems on the Miata and a solution whereby the author has changed the routing of coolant. I would suggest that you read this as it explains some of what you are doing on this engine swap.

The Escort and many other applications of this engine are front wheel drive meaning the engine sits sideways in the car. In those applications the coolant from the rad enters the water pump at the bottom on end and travels through and up the block to exit via the heater and thermostat housing on the other end of the engine. Apparently this is the original design of the cooling routing. Miata, being a rear wheel drive car, had the coolant actually exit the top of the block at the front through the Thermostat housing and also out the back to the heater. This meant that the back cylinders always run hotter. By retaining the original design you have better cooing and do not have to change the complete thermostat housing on the 1.8. The down side is that you must route the coolant from the back of the engine to the rad and the thermostat is on the back of the engine in a very ignorant location to get at!

I suggest using the Thermostat housing from the 1.6 because is has a better angle to route the coolant up to the front. The one on the 1.8 has an angle that would mean the hose would hit the fire wall on installation.

I am using a 90 degree 1 ¼ inch rubber rad hose coming off the Thermostat housing and pointing up. I then attach one of the chromed sink tube 90 degree pipes to the hose attached to a short piece of rad hose, a 6 inch straight chromed sink tube and then another piece of rad hose and then another 90 degree sink tube. This brings the coolant around the front of the motor and with another shortened 90 degree tube it will connect to the original rad hose. My theory is that the sink tube is chrome plated brass so it will not rust. It is thicker wall than the heater tubes and it holds the pressure and the chrome looks great. You will have to experiment with clamps. On the tubes I used one end had a ridge on it so I use the original wire clamp with each wire on a side of the ridge. The other ends were straight so I used a good quality stainless steel gear clamp. No leaks at all.

This routing not only provides better cooling you can use the original front timing cover as received with the 1.8. (An alternative would be to transfer the complete thermos housing from the 1.6 front the front of the 1. if you wished.)

There is another outlet beside the thermostat housing that allows coolant to go the oil cooler (see next) and also a small outlet to go up to the Throttle Body Control valve and then on to the water pump inlet. (In the 1.6 the coolant comes out of the block via the intake manifold and then to the air valve.)

Oil Cooler

The Escort comes with a cooler at the base of the oil filter. Coolant from the engine outlet at the back runs to the oil cooler and then to the heater inlet. I am very curious just how that works. The coolant comes from a hot engine block to "cool" the oil?? Maybe it is all relative. I think the later Miatas have the same as do some motor cycles. It works very well so far.

Coil Pack mounting

The Escort head has a couple of different things on it than the Miata such as vent placement for the valve cover and some other lugs etc. If you use a Miata 1.8 valve cover you will not have to worry about the vent coming out the rear as below.

Valve cover venting

The Escort valve cover does not have a vent on the side as the 1.6 does, it exits on the right hand rear side right in the middle of where the coil pack is mounted. I used a piece of thin wall clear 3/8 tubing off the vent outlet and then ran the line back to the intake. The thin wall tube was required so it did not interfere with the coil wires.

If you have a 1.8 valve cover then you do not have the venting pipe to clear and you would not to make the notch etc in the coil pack.

Oil Pan Change

Install the engine and tranny

On first try the engine would not start. Where to start??? I tested all relays as per the Haynes manual and everything checked 100%. I then pulled a plug and turned the engine over looking for spark. Lots of spark, however I did not know if it was timed correct or not. Next I shot some starter fluid into the PVC connection and it tried to start. OK now we have a fuel problem. Checked fuel pump (jumper wire trick)and it worked fine. I had put the injectors from the 1.8 Escort engine in the engine so I changed them back to the 1.6, tried again no start. Think, Think Think, next I checked the fuel line arrangement and went to bed thinking about it. In the engine removal I had marked lines but the markers were in poor shape and I began to questions what was happening and felt sure they were backwards. Next evening I reversed the lines and tried again, started and ran great on first turn! NO leaks!!!!!!!!!!!!!!!!!! Every British car I have worked on had many leaks especially on first start and this one was dry. Good oil pressure, good sound and so I let it warm up completely adding antifreeze and water in equal measures. On first start I had HLA noise but this stopped after warming up and pressures got up.

I took it for a test drive that weekend and that was my first drive in any kind of Miata. For an automatic it had great pickup and ran excellent. I tried the Escort injectors again, no go. I assume they are a different voltage and maybe pressure. I got a used set of Miata 1.8 injectors from ebay and they seem to work great. Note: I damaged an oring on one of these as well and find the orings quite easily cut, be carefull!

Power steering seemed hard but after I topped up the fluid it worked great. Automatic seems perfect. Could not get the cruise to work and only discovered it has an on off switch on the dash after I got back from the drive doh!!!!

Air-conditioning does not seem to work. I will do that later.


Did the check and set it at 10 (Auto), so far runs great.

I have now driven the car for 2 months. I should say my wife has driven the car as daily driver for 2 months. I have not had one single problem except a little leak of tranny fluid from the modulator valve which I think I may have bumped when installing the engine. All systems except AC worked from day one. Off the line pick up is very good considering it's an automatic and reliability is great. I have never actually driven a 1.6 Miata so I cannot compare but for what I spent on this swap and how it runs I could not be happier. I have many pictures and if anyone wants a more detailed explanation of how to do this please email me at any time. Using the Escort engine is a lot more hassle but in my case it was far cheaper. I am not really sure how the compression ratios etc for the Escort compare to the Miata 1.8 so maybe that information can be found elsewhere.

I have to give major credit to many members of the forum whose posts I read and learned from. I do not think I could have done this without the collective wisdom available on the forum. For those of us old guys who remember days before the internet it is amazing what can be learned! Good luck

Back to the Garage

25 June, 2006