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 Miata.net 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.
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:
- A dead or dieing Miata.
- Donor engine. Look on the Miata.net for lists of compatible engines. I bought
a 91 Escort GT DOHC 1.8L with 53 K. I have found that many sellers on eBay
say 50 k on any used engine that is sold but after I received this one it
looked and tested almost new so I have no reason to think it was anything
more. The most noticeable visible difference on the engine is the large FORD
logo on the valve cover but given that Ford and Mazda are related, this does
not give me any problem. If that does not work for you, then you will need
a new/used Mazda cover as well.
- Fuel rail from a 95 to 97 Miata 1.8. I bought mine used on eBay for $39.00
plus shipping. Note: I thought I could use the fuel rail from the Escort by
grinding away some metal on the intake. I did a fair amount of grinding and
it still did not fit so I ordered a used rail. I do think that you could do
enough grinding to make it fit but it might look a little funny and not be
- Intake from a 95 to 97 Miata 1.8 l I got mine for $69.00 used and powder
coated on eBay.
- Intake Manifold Stay, also called support bracket. I have mixed feelings
on this. Neither the 1.6 or the Escort bracket will fit. I think you could
just leave it off as the weight of the manifold does not seem too heavy as
to break the mounting lugs compared to most other cars. If you read this web
site you will find many references to leaving it off and unless you are racing,
that should work. If it was not installed it would also make getting to the
oil filter much easier.
- Oil pan from a 95 or newer Miata. The Escort is a front wheel drive car
with engine mounted sideways and the oil sump on the front. You will need
a rear sump oil pan from a Miata.
- Dipstick and Dipstick Tube The tube should be attached to the 1.8 Oil pan.
On the Escort the dipstick goes through the oil pump and into the front sump.
I cut the tube off and used the little rubber plug and clamp from the back
of the 1.6 to finish off the tube. The dipstick tube on the 1.6 pulls out
after the little bracket is disconnected. It has an o-ring on it that should
be replaced if you are going to use it in the 1.8. I had the tube but no dipstick
so I modified the Escort dipstick in the conversion and it works fine.
- Parts of the FM 1.8 to 16. conversion kit are nice but you cannot use the
complete kit as the coil mounting bracket will not work for this installation
(more on this later). Here are the parts you should buy from them individually.
- Throttle body adaptor
- Engine mounts
- EGR blanking plate (could be made from scrap but the one they sell is
- Throttle cable bracket, (again you could make one but the one they sell
- You do not need the CAS wire extension kit. It is simply 4 pieces of
wire and 10 connectors which you will likely already have.
- Exhaust Manifold from a 1.8 l Miata.
- Alternator bracket from a 1.8 if you can (if you cant or are too cheap like
me you can modify the 1.6 so it clears the intake manifold, you will need
to weld and grind at bit)
- Block heater if you need one.
- Gaskets for all manifolds etc.
- 4 feet of ¼ inch rubber hose for coolant sensor lines, must be able
to handle cooling system pressure.
- 4 feet of 3/8 inch clear tubing for valve cover vacuum routing
- 2 - 1 ¼ inch chromed sink traps ( do not laugh you will see them
later) These can be purchased in Lowes etc in the plumbing section.
- 2 - 1 ¼ Rad hose elbows. You could get these by purchasing an additional
Miata front top rad hose and cut out what you need.
- Remove hood from car being careful to scribe around the hinge locations
for proper fitting on installation and also save and mark hood bolts.
- Photograph the existing engine installation from all angles
- Remove intake box pipes wiring and label ends
- Remove all vacuum lines and label
- Remove all electrical connectors and label
- Drain coolant from engine and rad
- Remove upper Rad hose
- Remove Rad
- Unbolt Power Steering and wire it up and to one side out of the way
- Unbolt Power Steering mounting plate from engine saving bolts, you will
need if for the 1.8
- Unbolt AC pump and also wire it out of the way as far as possible
- Unbolt AC pump mounting plate from engine saving bolts, you will need it
for the 1.8
- Disconnect lower rad hose from engine and either remove it or turn it upright
out of the way to allow the engine to clear it when removed.
- Disconnect heater hoses, cut them off, these pipes are paper thin
- Remove water pump intake fitting and hose to heater outlet, you will use
this fitting on the 1.8
- Remove Alternator and brackets, you will use these on the 1.8 (note: try
to get an alternator bracket from a 1.8 it will be easier!)
- Remove Intake Manifold
- Remove Fuel rail and injectors,
- Remove Coil pack and bracket you will use this on the 1.8
- Remove the CAS you will use this on the 1.8
- Remove Oil pressure sensor, you will use this on the 1.8
- Carefully remove 1.6 engine wiring harness that connects all the various
sensors, you will use this on the 1.8. NOTE: The green square connectors on
the engine sensors usually have a small wire lock that is at the base of the
connector that need to be removed before pulling of the connector. You will
need a very fine end pick to remove this wire. You will damage the sensor
if you pull too hard on the green connector without removing the lock wire.
- Remove the Thermostat housing and Coolant temp sensor (Grey wire connector)
as a unit, you will use this on the 1.8 at the thermostat housing on the back
of the Escort engine. This sensor controls the rad fans.
- Remove the Coolant temp sensor (Green wire connector) on the heater outlet
fitting on the back of the 1.6, you will use this on the 1.8 engine, this
unit controls the ECU
- Remove the small Coolant temp sensor (one blade type connector) on the back
of the 1.6 you will use this on the 1.8, this unit feeds the temp gauge in
- Remove the "cursed coolant plug" from the back of the 1.6 engine,
you will need this on the 1.8 to plug the cut off dipstick tube on the oil
- Extend the 4 CAS wires about 6 to 8 inches so the connector will reach to
the LH side of the engine on the 1.8
- Find the connection for the forward Coolant sensor mounted on the Thermostat
housing and undo it from the other wires it is attached to. It will now need
to go the back of the engine as the sensor will be on the rear this time.
There should be enough wire to reach but if not you will need to extend it.
- The other coolant sensor attachments are still at the back and they should
reach everything fine.
- Proceed to "Donor Engine section"
- Pull out the engine complete with tranny after disconnecting all tranny
stuff and engine mounts and exhaust pipes etc. (all easier said than done.)
- This is also the time to repaint the engine bay or at least clean it up
and check for nasty things. Also easy to get at rack and pinion steering boots
Donor Engine 1.8 liter
- Mount engine on a moveable portable stand or get it close by for trial mounting
of items from the 1.6
- Remove intake, exhaust, water pump inlet, distributor, and spark plug wires,
engine mounts and set aside, you will not use these but little brackets or
spare bolts from them are handy to have around.
- I used the injectors from the 1.8 escort engine and the fuel pressure regulator
but they do not run on the Miata so I ended up installing the 1.6 injectors
and FPR and it worked to get it running. I am not sure what the difference
is in the injectors or FPR but mine would not work.
- Temporarily install fuel rail and injectors, intake and exhaust manifold
on engine (these are the ones you bought). If you can just set them on to
see how they fit and make sure everything is ok, do not bolt them up yet.
- Temporarily install wiring harness from 1.6 and adjust around rail etc for
best fitting so when it is done after the engine is installed you know how
it will fit
- Alternator mounting bracket. The bracket from the 1.6 bolts right up to
the 1.8 but the design interferes with the 1.8 intake manifold mounting. I
ended up modifying the one from the 1.6 to work on the 1.8 but it would save
some hassle to get one from a 1.8 Miata engine.
- I would suggest putting the intake manifold, exhaust manifold, fuel rail
and wiring harness and alternator on after the engine is installed in the
- Remove the oil pressure sensor on the 1.8
- Install block heater on in the larger frost plug next to the oil pressure
sensor and oil cooler
- Install the 1.6 oil pressure sensor in the same location as the one from
- Install power steering brackets and also AC brackets from 1.6
- Install Water pump inlet and heater hose pipe taken from 1.6 use new gasket
and O ring. The 1.8 is longer than the 1.6 so the fitting on the heater hose
pipe will not match up with one of the exhaust manifold bolts like it did
on the 1.6. I cut piece of metal from scrap and welded it sideways to the
bracket to reach the next bolt. I believe this is required to keep the pipe
in the water pump inlet and the Oring in place.
- On the back of the assembled 1.8 engine is a coolant sensor on the Thermostat
housing. It is sticking straight out and will hit the firewall when the connector
is on so you will have to modify this one as well. I carefully mounted the
sensor in the vice and with a hacksway cut away the plastic housing around
the straight metal wire pig tail. Then I carefully bent the pig tail 90 degrees
so a wire can be hooked on from the side. I made a connector from a stock
female connector and some heat shrink. This saves almost 3 inches of space
and means you do not have to take a hammer to the firewall.
- Test fit the CAS from 1.6 engine to the 1.8. It mounts on opposite side,
use new O ring. I found to install the CAS on the escort engine after the
engine is installed means removing the valve cover. If you install the CAS
before installing the engine there is danger in it being damaged as the space
is very tight
- Install Thermostat housing cap from the front of the 1.6 on the back of
the 1.8 in place of the one that the 1.8 came with. The reason you do this
is that the 1.6 housing is a 90 degree angle and the 1.8 from the escort is
more like 45 degrees. It would mean the outlet hose would hit the firewall.
Make sure you have a new thermo gasket and thermostat is installed. I used
the one that came with the 1.8.
- Install one of the 1 ¼ inch rad hose elbows along with clamp on the
thermostat housing (see Cooling Reroute below). It will be much easier to
do this now than after engine is installed.
- Remove the Coolant temp sensor (Green wire connector) from the Escort engine
and install the one from the 1.6. They look the same but the numbers on them
- Remove the small Coolant temp sensor (one blade type connector) and install
the one from the 1.6 so it will talk to the gauge in the Miata. It is on the
opposite side of the block but the wire should reach.
- This means that all 3 temp connectors are now on the back of the engine.
- Remove the intake, exhaust fuel rail, harness and alternator brackets and
install them after engine is in the car.
- Now is a good time to clean the intake manifold and also polish and or port
the head and intake.
- Mate up the transmission to the engine doing what ever you should do ie
new clutch etc. I checked out the vacuum modulators and other lines and cleaned
up the exterior of the automatic.
- The engine should now be ready to install in the car
- Prior to installation I strongly suggest you double check all the stuff
on the back of the engine for tightness, that is one ignorant place to get
at after the engine is in! I did this and have not leaks thank goodness!
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.)
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.
- Remove coil pack from 1.6 bracket, you will install it later
- Cut a notch in it to allows the coil wires to lead off the pack to the rear
without being bent upward.
- File a round end in the notch to allow the vent tube for the valve cover
vent to go between the two middle plug wires.
- Cut off the bottom round lug on the bracket as it will be in the way.
- Remove the right hand rear engine lifting lug from the 1.6 and install it
in place of the one on the 1.8, note the different locations. You will note
that the 1.6 lug has a little bracket on it. Leave that in place, you will
- On the back of the 1.8 there are 2 lugs on the head they are for mounting
some small brackets, remove these brackets. The coil bracket will now bolt
to one of those lugs with the bolt in it pointing down and the other side
of the bracket will bolt under the lug bracket with the bolt pointing up.
Overall the coil bracket is now lower than original but is firmly attached
and level. Neat!
- If you turn the CAS you will see it will interfere with the newly mounted
Coil bracket so you must grind off some material of the coil mounting bracket
to allow it full movement.
- After I did the cuts and grinding I painted the coil bracket and reinstalled
- I shortened all the plug wires to make a nice neat installation.
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
- Remove the 1.8 oil pan and also the oil sump pickup
- The Escort has a spacer under the oil pan lip that you may or may not need
depending on the type of pan you bought.
- My old 1.6 had a windage tray on it that requires the holes to be re-drilled
to fit block holes on the 1.8. The oil pump pickup is also needed from the
1.8 and the windage tray needs to be attached correctly for the pick up tube
to attached to it. I had to make little aluminium spacers to fit compensate
for space left by the shorter 1.6 windage tray.
- Install the oil pump sump pick up you bought and torque to require value
using lock tite.
- Install the new oil pan using new front and rear seals and the required
silicone seal for the gasket.
- You can install the dipstick tube from the 1.6. I am making a new stick
as my 1.6 did not have one.
Install the engine and tranny
- After the complete built up unit is ready install in the car using new engine
- NOTE: if you feel unsure about damaging the rear coolant sensor in the Thermostat
housing during engine install, take if off and install it after. It is not
that cheap and can be broken easily.
- After I installed the engine and tranny and tightened it all up the engine
looked like it was sitting a bit high in the front and the room at the back
of the engine to firewall was very tight. Reading on the forum brought up
information to correct this. The rear of the tranny connects to the rear end
via a metal web (PPF). You need to jack up the rear of the tranny before you
tighten the bolts to the web. The tips the front of the engine down and increases
space between engine and firewall. I would never have thought of this if someone
did not post it on the forum!
- Install Alternator bracket and belt
- Install Intake and Throttle body unit together
- Install Injector and Fuel rail and wiring harness
- Install lower wiring harness to block heater, oil pressure sensor and alternator
- Connect all wiring harness on this side.
- Run new length of heater hose from oil cooler outlet to heater inlet, I
ran this around the front of the engine as it seemed to create fewer sharp
- Run length of ¼ inch coolant hose from outlet at back of block to
Throttle body valve then another length over to water pump inlet down by the
- Run required vacuum hoses to intake throttle body etc
- Install ac pump to bracket
- Install pwr strg pump to bracket
- Install heater hose from outlet to pipe on water pump inlet
- Exhaust Manifold and O2 sensor.
The 1.6 has the O2 sensor on the outlet of the exhaust manifold while the
1.8 has its sensor in the pipe that leads to the cat. I removed the O2 bung
from the 1.6 manifold (I used a cutting wheel) and after drilling a hole in
the 1.8 manifold pipe I welded it on. I think you can buy an O2 bung but it
was quicker to do it myself this way. I also welded up the EGR outlet on the
1.8 manifold as you do not need it.
- Install exhaust manifold and pipes and heat shield. The heat shield will
need to be modified to allow the O2 sensor to be installed. I just used some
tin snips and cutting wheel to cut away the corner.
- Manifold on mine bolted right up to the pipe and the pipe to everything
- Run the rear exit rad connection around the engine and to the rad as per
- Intake Air System
- Because the 1.8 is a long block and you are installing an FM adaptor
plate to the intake the air intake system will not fit without some modifications.
There is a kind of a square chamber attached to the intake pipes; I removed
it completely and capped of the inlet to it. There is no way it will fit.
I read somewhere that it will not likely upset performance unless you
are racing in which case you will likely have a different intake anyway.
- I had to grind off one rad fan support bracket on each fan to allow
the intake to fit. This still leaves 3 for each fan.
- Install intake air set up wires vacuum and sensors etc
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
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