Mazda B-Series Engine Swap FAQ

This engine swap FAQ details the differences between OBD-I Mazda B-series naturally aspirated 4-cylinder engines. This guide was created to help people making the transition from one B-series engine to another with ease.

I. Applicable Cars for this FAQ
II. Stuff you should know about engine swapping
III. Parts you may want to consider replacing (in order of importance/necessity)
IV. Tips on buying a good used engine
V. B-Series engine run down (B3-E, B6-E, B6-ME, B6-DE, B8-ME, BP-ZE)
VI. Swap information:
VI-a. Engine Mounting Points
VI-b. Intake Manifold
VI-c. Exhaust Manifold
VI-d. Wiring Harness
VI-e. ECU & TPS sensor
VII. Transmission, Clutch & Flywheel information


I. Applicable Cars:

This FAQ details how to swap any B-series engine into your Mazda vehicle. This guide is applicable towards the following models (possibly more):

1989-1993 Ford Festiva (1.3 SOHC 8v)
1990-1994 Mazda 323 (1.6 SOHC 8v [Federa] & 1.6 SOHC 16v [California])
1990-1994 Mazda Protege SE & DX & 4WD (1.8 SOHC 16v)
1992-1993 Mazda MX-3 (1.6 SOHC 16v)
1994-1995 Mazda MX-3 (1.6 DOHC 16v)
1994-1997 Ford Aspire (1.3 SOHC 8v)


II. Stuff you should know about engine swapping:

Before I get into the details about these engine swaps, I want to ensure you know what you are getting into. All of these engine swaps are VERY easy for a beginner to perform themselves in a 2-5 day period. It should not be difficult to do this swap as long as you don't run into any stubborn bolts. I'm not going to write a step-by-step process for removing and reinstalling the engine in this FAQ. You can perform any of these engine swaps with basic hand tools. You should have a screwdriver, set of pliers, and ratchet with set of metric sockets. All of the nuts and bolts on all of these engines are either 10, 12, 14, or 17mm in size with few exceptions. The axle nuts are 32mm (29mm on aspire/festiva) and are a ***** to remove without an impact wrench. Using a penetrating solution will aid in the removal of corroded bolts. Using high-temp RTV silicone gasket maker will ensure you won't have any leaks. You can even reuse old gaskets if you use this stuff, although it isn't recommended. Below is a list of suggested parts you should replace prior to installing your new B-series engine.


III. Parts you might want to consider replacing (in order of importance/necessity):

-Oil filter & Oil: You spent all this money on a new engine, why wouldn't you change the oil?
-Spark plugs: Come on you cheapass!! AT LEAST replace the plugs on your new engine. They are like $2 or less for NGK V-powers (the only plugs shy of iridiums you should use on any B-series mazda engine). They are easy to replace too!
-Air filter: Why not replace this? Most of you will probably use an aftermarket air cleaner system anyways, but if you aren't, you might as well spend the $4 on a new air filter for your airbox-Valve cover gasket: Is the engine covered with oil on the head? if so, the valve cover gasket probably leaks. Replace it! They are $8-18 from any autoparts store
-Transmission fluid: Don't be a bastard and use ATF in your tranny, get 75w80 or 85w90 for ur tranny (whatever is recommended). Redline and Royal Purple & Amsoil make great fluids that will make your shifting much smoother, so you might want to look into them if you don't mind spending $10 a qt.
-Clutch Kit: You will be removing the transmission to swap engines, so you might as well replace the clutch if it needs it. DON'T get a crappy "in-house" clutch for $80 at your autoparts store either. Get a name brand one. Exedy's are great OEM replacements and will hold up to most any naturally aspirated BP. I detailed information about clutch swapping in the "transmission" section of this FAQ.
-Exhaust & Intake manifold gaskets: Did you remove the intake or exhaust manifolds when transporting the engine? If so you should replace these gaskets. It isn't a bad idea to replace these anyways since a coolant leak into the airchamber isn't a good thing, neither is an exhaust or air intake leak. Either Exhaust or intake manifold gaskets run about $12-25 depending on the engine and usually require special order from auto parts stores.
-Throttle body gasket: Not all that necessary, but if you did remove the throttle body, you should replace this gasket. It most likely will flake apart on you when you remove the TB anyways. These gaskets are cheap and usually in stock, about $8 for one.
-Sparkplug wires, distributor cap & rotor: Might as well replace this stuff too while your at it, although it isn't super necessary, it'll ensure your engine will run tip-top and get the best fuel economy.
-Thermostat & gasket: It is very easy to replace the thermostat when you have the engine out of the car. For all you know the one in the engine is defective! They are like $8-10 and the gasket is $1.29 so why not replace it? They sell them in 175, 185 and 195 even 205 degree's. 185 is OEM on most of the B-series engines, but if you live in a different region, you might want to go with another temperature thermostat.
-Accessory & Water Pump belts: Easier to do these when the engine is out of the car, so might as well! They are like $4-10 each
-Timing belt & Water pump: If you are going to replace one, you might as well replace the other. On B-series engines, the water pump is right under the timing belt. And if you have to replace the water pump by itself, it'll require you to remove the timing belt, so DO BOTH! Timing belts are $40 for the SOHC's and $55-75 for the DOHC.
-Oil pan gasket: Not all that necessary, but if it has an obvious leak, it is MUCH EASIER to replace it now. They cost about $15, be sure to torque the bolts properly, they are very easy to break if overtorqued so be careful!.


IV. Tips on buying a good used engine:

Mileage isn't everything when it comes to used engines. Just because an engine has 40k miles on it doesn't mean its a better choice than the 110k mile one across the yard. Of course it is entirely up to you and your budget for an engine, but a good bet is an engine under 120k miles old. B-series engines are pretty damn robust and are built for turbocharging. Their cast iron blocks don't wear fast. The most notable problem with them is their tendency to have the famous "valve tap" issue due to the HLA system Mazda used in their BP models. Burnt valve seals also can cause the engine to burn oil, and there really isn't any way to tell if the engine has this problem without starting it up and revving it.

Here is a quick & short guide on how to choose your engine:

Always pop off the valve cover & inspect inside of the valvetrain:

-If inside of head is SILVER.............the engine has been religiously maintained, including the use of a high-quality oil that didn't varnish the internal parts. This would be a rare find & great candidate to install into your car.
-If inside of head is GOLDEN.............the engine has been maintained properly, it is a good candidate. The golden color is "varnish" caused by years of use of dino oil. Assuming no sludge buildup is present the engine should be a good pick.
-If inside of head is DARK BROWN..............the engine has probably missed its oil change on more than one occasion. Depending on the mileage of the engine, it still could be good. Anything under 60k miles with carbon deposits will likely still be fine to use, but anything over that might have other problems
-If oil inside head is CREAM COLORED.............then water has contaminated the oil. This means blown head gasket & most likely a lot of internal wear & tear has already occurred. Using this engine & ensuring it will work properly may require a thourough rebuild.
-If the inside of head is BONE DRY...............then this motor has been sitting for over a year or two. This can mean the seals & gaskets have lost their "lubrication". This may cause them to leak once you begin using the motor. Depending on the mileage & how the rest of the head looks (golden or brown), the engine is still good, but will require special attention to replacing its seals.
-If the outside of the engine is CRUSTED WITH OIL............then the motor has a gasket leak somewhere. It is usually easy to tell where this is. This isn't necessarily a bad thing, but does indicate the previous owner didn't look under the hood all that often. If the head is golden, it shouldn't be a problem, but if the head has carbon deposits, there could be other problems with the engine (like low compression due to wear & tear).


V. B-series Engine Run down:

This section quickly details which year/make/model each B-series 4-cylinder engine comes from, the HP and Torque ratings (from the factory) & fuel economy data on that vehicle. I also listed the weight of the vehicle in which the fuel economy data is from. This should help you calculate, roughly, what kind of fuel economy you can expect your car to achieve, if you compare your cars weight to the weight of one of these cars.

I will refer to each of these engines by their engine code from this point forward:

1.3 SOHC 8-valve
1989-1993 Ford Festiva [1787 lbs.]
1994-1997 Ford Aspire
63hp @ 5000rpm
73ft-lb @ 3000rpm
36/42mpg (5spd manual)
29/34mpg (3spd auto)

1.6 SOHC 8-valve
1985-1989 Mazda 323 (exc. GT & GTX)
1988-1989 Mercury Tracer
1990-1994 Mazda 323 (federal) [2238 lbs.]
82hp @ 5000rpm
92ft-lb @ 2500rpm
29/37mpg (5spd manual)
26/33mpg (4spd auto)

1.6 SOHC 16-valve
1990-1994 Mazda 323 (California)
1992-1993 Mazda MX-3 RS [2332 lbs.]
88hp @ 5000rpm
98ft-lb @ 4000rpm
29/35mpg (manual)
25/32mpg (auto)

1.6 DOHC 16-valve
1994-1995 Mazda MX-3 RS [2443 lbs.]
105hp @ 6200rpm
100ft-lb @ 3600rpm
29/37mpg (manual)
25/34mpg (auto)

1.8 SOHC 16-valve
1990 Mazda Protege SE
1990-1991 Mazda Protege 4WD
1991-1994 Mazda Protege DX [2359 lbs.]
103hp @ 5500rpm
111ft-lb @ 4000rpm
28/36mpg (manual)
24/31mpg (auto)

1.8 DOHC 16-valve
1990-1994 Mazda Protege LX [2480 lbs.]
1991-1993 Ford Escort LX-E
1991-1996 Ford Escort GT
1991-1996 Mercury Tracer LTS
125hp @ 6500rpm (127hp @ 6500rpm on Ford & Mercury models)
114ft-lb @ 4500rpm

One thing to note about all of these engines is the ECU and TPS differences between manual and automatic transmission cars. The throttle position sensor is different between manual and automatic transmission cars and will not interchange. Manual transmission cars have a 2-plug ECU while automatic transmission cars have a 3-plug. These ECU's will not interchange without serious splicing!! It is best to get an engine from a car with the same transmission that you have.


VI. Swap Information:

As stated before, this guide is not going to include a step-by-step process for removing/installing your new engine. This section will outline the differences between the engines listed above and how you can fit one of these engines into your car.

VI-a. Engine Mounting Points:

90-94 Protege & 323, 92-95 MX-3, Ford Escort GT & LX-E, Mercury Tracer LTS are all the same. You shouldn't have a problem interchanging motors between these cars. In the event you do need to change mounts, just unbolt the mount bracket from your old engine and bolt it to the new engine.

Ford Festiva and Ford Aspire mounts will interchange with each other. The passenger-side mounting bracket from your B3 will directly bolt up to the B6-E and B6-ME engines. You will need to fabricate a custom passenger bracket if you plan to swap a B6-DE, B8-ME or BP-ZE to your Festiva or Aspire. The transmission mounts should be left untouched unless you plan to do a transmission swap.

VI-b. Intake Manifolds:

For 85-89 323, 89-93 Festiva and 94-97 Ford Aspire only. Unless doing a B3 to B6 (from older 323) swap, you will need to use the intake manifold from the engine you are putting into your car. Since your car has its intake routed over the top of the valve cover, you will need to figure out a way to rig a drivers-side mounted air cleaner assembly to your car. The MX-3 B6-ME comes with an intake tube that will allows you to rig the air cleaner to the side with ease, but you WILL have to relocate the battery, or go with a super-small sized battery to provide enough room for the aircleaner assembly. You can NOT interchange intake manifolds between these engines, the water coolant jacket locations and intake port locations are different on almost all of the B-series engines

VI-c. Exhaust Manifold:

Unlike Honda B-series, Mazda B-series exhaust manifolds (headers) DO NOT interchange between each other. This means you will need to use the stock exhaust manifold from whatever engine you are installing into your car. If there are headers available for that engine, then you are in luck, but headers are hard to find for any engine besides the BP-ZE, unfortunately.

VI-d. Engine Wiring Harness:

To simplify my findings, I made a list of three different style engine harnesses that are used for the non-OBDii B-series engines:

Style "A":
Found on 85-89 Mazda 323 & Tracer B6-E, Ford Festiva B3-E. This harness has a different style IAC valve plug that is blue in color, but still uses two wires. The distributor plug has three wires. The fuel injector harness includes the TPS sensor plug.

Style "B":
Found on 90-94 Mazda 323 B6-E & B6-ME, 90-94 Protege B8-ME and 92-93 MX-3 B6-ME. This harness has a newer style IAC valve plug that is used on all "driver side routed" intake manifold designs. The TPS sensor is part of the engine harnses and not the injector harness. This harness has a 3-plug distributor connector.

Style "C":
Found on the 90-94 Mazda Protege BP-ZE, 91-96 Ford Escort & Mercury Tracer BP-ZE. This harness has the newer style IAC valve plug, and its TPS sensor is not part of the injector harness. This harness includes an additional 2-wire plug for the variable induction control system solenoid (V.I.C.S.). This harness has a 4-plug distributor connector.

Unfortunately, I am unsure of what the 94-95 Mazda MX-3 has. I have a hunch it has the "Style B" harness.
Also the 94-97 Ford Aspire. I know they used MAF's instead of VAF's for airflow readings. Their harnesses might only be different in that area, but I am not familiar enough with them to post that information here.

Another thing to note is that all 1996 Ford Escorts and Mercury Tracers have an OBDii engine harness which is very different from the OBDi version. While there weren't many of these cars made, it might be very difficult to get your OBDi harness to work with the OBDii engine without swapping out all of its sensors.

Now that you know the differences in each wring harness, it should be easy for you to wire your new engine using your harness. Here is a quick rundown:

Style "A" to Style "B" Engine: you will need to get the IAC valve connector from the style B harness and splice it into your existing harness. There is a thicker wire and a thinner wire, just splice the thick and thin wire from the connector to the thick and thin wire on your harness. You will also need to remove the fuel injector harness from you new engine and reuse your old fuel injector harness to ensure the TPS works.

Style "A" to Style "C" Engine: You will need to do everything listed above and also get the two-wire connector from the VICS solenoid and route those two wires all the way to the two pinouts on the BP ECU you are using. You will also need to get a 4-wire distributor connector, and splice the three wires from your old harness, and route the forth wire to your new BP ECU.

Style "B" to Style "B": No splicing is necessary!

Style "B" to Style "C": You will need to get the two-wire connector from the VICS solenoid and route those two wires all the way to the two pinouts on the BP ECU you are using. You will also need to get a 4-wire distributor connector, and splice the three wires from your old harness, and route the forth wire to your new BP ECU pinout.

VI-e. ECU & TPS Notes:

Be sure to use the ECU from the car your new engine is from, otherwise the engine will not run at it's full potential (if at all). One thing to note is the differences between manual and automatic transmission cars. The TPS is different between these cars and will not interchange. 5-speed cars have a 2-plug ECU while Automatic transmission cars have a 3-plug ECU. Interchanging these ECU's will require serious splicing, so be sure to get the proper ECU for your car. It is also easier to get an engine from a car of the same style transmission to avoid the TPS interchangability problem.


VII. Transmission Information:

To clear up any confusions, you must understand that all of the cars listed above have transmissions that will directly bolt onto ANY of the engines in this FAQ. YES YOUR TRANSMISSION WILL BOLT UP!!! Now that you know that, you might be wondering about possibly swapping your transmission for a stronger G-series transmission. If you have a 323, MX-3 or Protege DX, you have a Mazda F-series gearbox. This transmission should hold up well to any of these engines. It has taller gear ratios which are geared for fuel economy over performance and smaller, 22mm diameter axles. It has been known to hold up to about 200 horsepower and ft-lbs of torque without reliabilty issues when not abused.

The Protege LX, Escort GT & LX-E and Tracer LTS all have G-series transmissions. These transmissions are used in numerous Mazdas including all 2.0 4-cylinder & 2.5 V6 MX-3, MX-6, 626, Ford Probe and 01+ Protege's. They have been known to hold up to over 300hp and ft-lbs of torque when not abused. They use 24mm axles and utilize an intermediate shaft to reduce torque steer when accelerating off the line. All G-series transmission have either a 4.11 or 4.39 final drive ratio and short gear ratios for quicker acceleration at the expense of fuel economy.

To swap a F-series for a G-series, you will need to get the axles, intermediate shaft from a 90-94 Protege LX, 92-94 MX-3 GS or 91-96 Ford Escort GT/LX-E or Tracer LTS. The hubs & brakes do not need to be swapped out on any of these vehicles. Swapping the other parts out will allow you to use one of these transmissions. Be sure to get the transmission mount brackets & mounts when you buy your transmission as they will be needed to mount it.

Clutch & Flywheel Information:

There are 5 different sized clutches worth noting that can be used on these engines. Here is the list:

B3-E: 7 1/8" Clutch Disc, 18-spline shaft, 3/4" hub
B6-E & B6-ME: 7 1/2" Clutch Disc, 20-spline shaft, 7/8" hub
B6-DE & B8-ME: 7 7/8" Clutch Disc, 20-spline shaft, 7/8" hub
BP-ZE & K8-DE: 8 1/2" Clutch Disc, 22-spline shaft, 15/16" hub
2.0 SPI (From 97+ Escort) & KL-DE (Probe GT, MX-6 LS): 8 7/8" Clutch Disc, 22-spline shaft, 15/16" hub

The 20-spline shaft clutches are for F-series transmissions only. You *should* be able to use the bigger-sized clutch on a B6-E or B6-ME flywheel for more clutch holding power, although it has not been confirmed. The 22-spline shaft clutches are for G-series transmissions only. You can use the bigger-sized 8 7/8" clutch from the Ford Probe / Escort on a stock BP-ZE flywheel for more clutch holding power.

The flywheels from all B-series engines will interchange with one another and use 6-bolts to secure them to the crankshaft. K-series V6 engines use a 8-bolt flywheel and thus are not interchangable