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.

Overall Advice

Photographs

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.

Safety

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 correct.
  
• 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 very nice)
    
  • Throttle cable bracket, (again you could make one but the one they sell is nice)
    
  • 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.

Car work

• 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 the dash
  
• 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 pump.
  
• 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 etc etc.

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 car
  
• 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 the 1.8
  
• 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 are different.
  
• 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!

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.

• 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 need it.
  
• 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 the coils.
  
• 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 mounts
  
• 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 wires
  
• 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 bends.
  
• 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 ac pump
  
• 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 down.
  
• Run the rear exit rad connection around the engine and to the rad as per above
  
• 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.

Timing

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