by Joseph Toronto
This info is good for someone on a tight budget who wants to replace a bad motor in a miata already equipped with a 1.8. My work was done on a '94 Miata, newer ones may vary. The moral of the story here is that a Ford Escort 1.8 or equivalent is a viable low-cost alternative to a genuine Miata long block with very few drawbacks. It's the same motor, with the same performance characteristics. Just a little extra labor is required to make it work.
As the Escort (or Protege, or whatever) motor itself is the same thing. Everything attached to it is different. That means you'll be re-using nearly every piece bolted onto your old Miata motor. The list entails:
-intake and exhaust manifolds
-oil pan, strainer and windage tray
-bracket for the p/s pump (a/c bracket is actually the same on both)
-water housing on rear of engine
-thermostat housing on front (more on this later)
-crank pulley and water pump pulley (more on this later)
-oil pressure sender
-motor mounts and brackets
-spacer plate on back of motor
-engine lift hooks
-water pipe going from water pump to back of motor.
-Timing backplate & timing covers
That's all I can recall but you get the basic idea. The easiest way to do this is strip the major parts off the old motor and then keep it nearby so you can use the old motor for reference while putting the new motor together. What I also do is after I remove a part (bracket, etc..) from the old motor I put it's bolts back in their holes so I know which bolts go where as I put the new motor together. That way they wont get lost and you wont get confused.
Now there are some slight modifications that need to be done to the Escort motor to make it work. None of which are difficult or require any type of exotic tools.
Thermostat housing/tower: Since the Escort has it's thermostat on the back of the head, it has a freeze plug where the Miata's thermostat housing goes. Fortunately the bolt holes are already pre-drilled/tapped and only the freeze plug needs to be removed. I removed it by using a center punch and hitting it towards the top of the plug, essentially flipping the thing sideways like a coin. Then go in there with a pair of pliers and rip that sucker out. Then bolt the Miata's thermostat housing in place. That's it.
Crank pulley and water pump pulley: There's only one thing to watch out for here. Like early miata's with the 1.6 engine, the Escort motor can also have either a long or short nose crank. The split was in '91 just like the Miata. If you've got a long nose crank. You can stop reading. If you've got a short-nose crank (like I did) it's simple. You will re-use the Escort's crank pulley, sprocket, bolt etc... and it's water pump pulley. Then you need to get an alternator (or just the pulley) from a 1.6 Miata. The reason for this is that the 1.8 Miata uses a ribbed belt for the alternator/wp. Since that pulley wont fit on a short nose crank, you'll need to use the earlier style v-belt pulley which is common on Escorts and 1.6 Miatas. Also if you're replacing the front crank seal, you'll need to get one for an early '91 Escort. Most auto parts stores will list one that will fit 91-96 and one that will fit just '91. The latter is the one you want.
Alternator bracket: The difference is this. The 1.8 Miata attaches the upper part of the alternator (the part with the tensioner) via a mounting ear on the water pump. The Escort water pump doesn't have this mounting ear and instead uses an ear on the motor mount bracket hanging off the front of the motor. Now maybe as a matter of coincidence (probably not) the 1.6 Miata uses the same water pump as the escort. Meaning it too lacks the mounting ear. So how does the alternator attach on a 1.6? 1.6 Miata's have a separate bracket, that has the tensioner built in. You will need to get that bracket, it's associated hardware, and the 2 longer mounting bolts that it uses. I got this from Planetmiata.com as well as the 1.6 alternator I needed for $75 shipped. They even threw in a couple of lollipops and stickers. Excellent company to do business with. After you get the bracket, you're not done however. The bracket and Intake Manifold will interfere with each other, so you need to break out the bench grinder (or whatever you have that will do the same job, and take a little off the rib on the bottom of the #1 intake runner. Grind a little, test fit it, then grind more if necessary. I took a little off the bracket as well. I got them to fit together but they're still touching. Not a problem IMO. One other thing. The bracket will obscure one of the intake manifold mounting nuts. You will need to install the intake manifold first and then install the bracket. After that the alternator will mount up nicely.
Dipstick tube: The Escort dipstick goes through a hole in the oil pump body unlike the Miata that has it in the oil pan. All I did was cut the tube short (maybe 2 inches protruding) and thread a bolt into it to plug it. I might actually use this as a turbo oil-return port one day.
Coolant gauge sender: The sensor that drives the coolant temp. gauge on the dash has different resistance values. This is the smaller one that has a single spade terminal. I broke the one on my Miata's motor trying to unplug it so I ended up using the Escort's sensor. My gauge reads wrong. It reads 3/4 when it should be 1/2. If you don't break your Miata sensor, swap it over. If you do break it, buy a new one.
Nubs on back of cyl head: There's two metal tabs/nubs on the back of the Escorts's cyl head. Something mounts to them, not sure what, and they're in the way of the Miata's coil pack. I used my trusty cut-off tool and sliced them off. You don't need to grind them flush as there's roughly 2mm or so of clearance between the coil pack and the head.Some other things to consider:
-Some of the mounting holes in your Escort motor (particularly for the motor mounts) have never been used before. So they may be a bit rusty and wont accept bolts. I had to retap a few of them.
-I purchased a gasket set that said it was for the escort/protege/miata. Seems it was actually just a gasket set for a escort/protege because there were some that didn't fit. The oil cooler seal and exhaust pipe (after manifold) were different. I re-used my old ones because they were still in decent shape.
-I've read some threads on miata.net saying that the Escort cams are "economy" cams and different than the Miata cams. This is untrue. They are identical in every way. It's not necessary to switch them over.
And here's what makes it all worth it. Cost. Here's what I paid for everything. I'll leave out things not related to the swap itself (tune up parts, clutch, replacement hoses, etc..):
'91 Escort motor 110k miles- $200
Timing belt kit (includes tensioner, idler, and belt)
and gasket kit- $91 shipped (from ebay seller "domesticgaskets")
1.6 alternator and bracket: $75 shipped
That's $366 compared to the $800-$900 I've seen Miata 1.8's go for. That's a big difference. Also, there's the matter of availability. These Escort motors are a dime a dozen, whereas the Miata motors are not. I picked up the Escort motor locally where I would've had to have a Miata motor shipped to me adding another $100 or so to the cost.
As far as performance? It's wonderful. There is no difference. You'll be happy you did this. I am.
|Back to Garage||
4 January, 2009