Here is a great guide posted by firstgenprotege on the Festiva list
From: "firstgenprotege" Date: Mon Aug 26, 2002 11:15 pm Subject: Engine Swap Questions ANSWERED
Well, after reading the same ol questions again and again as of late, i'll write out this summary guide about all the engine swaps you can perform:
Stock engine (B3) - 1.3 liter (1323cc) SOHC 8v. Puts out 63hp, poor high end power, average low-midrange power.
86-94 323 / 85-89 Tracer (B6) - 1.6 liter (1598cc?) SOHC 8v. Puts out 82hp, poor high end power, good low-midrange.
Installation: Bolts straight in, but you have to use the festiva's intake manifold if you use a 90-94 323 (maybe the older ones too) but they bolt right up so it doesn't matter.
92-93 Mazda MX3 engine (B6-ME?) - 1.6 liter SOHC 16v. Puts out 88hp, good high end power, good low-midrange power (thanks to the 16v's).
Installation: No one has really confirmed if the festiva manifold will bolt up to this head. It MIGHT, but the stock manifold form the MX3 has the throttle body going off to the drivers side of the car, so you will need to use the ECU and wiring harness to use that manifold. If the Festiva's manifolds bolt up, then GREAT! otherwise there isn't really a point to install this engine. As for engine mounts..i'm pretty sure they are identical to the B6-DE engine.
91-94 Mercury Capri Engine (B6-DE) - 1.6 liter DOHC 16v. Puts out 100hp. Great high end power, good low-midrange power.
Installation: Must use a special made engine mount for the passenger side mount. Otherwise the manifolds and everything clears the engine compartment. you wlil need the Capri's ECU and harness, and will likely have to relocate your battery to the trunk to fit all the intake tubing.
94-95 Mazda MX3 engine (B6-DE) - 1.6 liter DOHC 16v. Same engine as the Capri, but puts out 105hp. Great high end power, decent low- midrange power.
Installation: Same as capri..look above. HOwever, the intake manifold's throttle body goes off to the side, so you will need hte MX3's ECu and harness, along with all the intake plumbing. You will DEFINITELY need to relocate the battery. Using the Capri's intake manifold would solve this problem, however.
90-93 Mazda Miata Engine (B6-DE) - 1.6 liter DOHC 16v. Same engine as Capri and MX6, but mounted longitudinally, and uses RWD transaxle. It puts out 116hp. Great high end, great low-midrange power.
Installation: No one really knows if it bolts straight in (confirm this for me?). Since it is mounted longitudinally, it could have different engine mounting points. Also the coolant inlet/outlets are located in a different spot than the transversely mounted Capri and MX3 B6D's.
87-88 323 GT / 88-89 323 GT-X / 91-94 Mercury Capri XR2 Engine (B6- DET) - turbocharged 1.6 liter DOHC 16v. It puts out 132hp on stock ECU but can easily be tuned for over 200hp (crank). Unreal mid- highend power, good low end (drives about like a B6D capri up until about 2000rpm, then it FLIES).
Installation: You must use a custom bracket for the passenger engine mount (just like the B6D).
As for getting the engine running, you must take into consideration the fact it is TURBOCHARGED. You will need to first of all, get the piping properly mounted inside of the car, which takes up more room than a naturally aspirated engine.
Second, you must ensure you are giving it proper amounts of fuel to go with the extra air. you can use the Stock ECu and harness from any of these cars, and run stock boost (6.8 psi?). Or you can get a engine management system like a haltech which lets you fine-tune the turbo to your liking. (however this is VERY EXPENSIVE).
You can always just upgrade your car with the stock ecu and harness with a boost controller and beefed up fuel pump to ensure it gets enough fuel. This would be cheaper and your car would still be insanely fast.
90-94 Mazda Protege / 91-96 Escort GT and Tracer LTX engine (BP-DE)- 1.8 DOHC 16v (1839cc). Puts out 125hp / 114 torque and has a very flat powercurve. Great power all around the powerband.
Installation: the block is longer than the B6's so you'd need to make custom engine mounts, and maybe even cut into the firewall to fit the engine and its long intake manifold. Would require A LOT of modification, but it will fit under the hood if your are up to the challenge. You would probably need to use the G25M-R transmission as well, which would require even more custom fitting.
90-94 Mazda Familia / 323 GT-X & GT-R Engine (BP-DET) - 1.8 liter (1839cc) turbocharged DOHC 16v. GT-X puts out 180hp on stock ecu and GT-R puts out ~210. Engines have potential to reach well over 400hp at the wheels (but then the trnasmission explodes ;)). I would imagine, the mid-high end power would be ridiculous. Low end would be great as well.
Installation: i wouldn't think all the intercooler plumbing would be able to fit under the hood without gutting the car and custom welding a new engine comnpartment or something ridiculous like that. I don't think anyone has even attempted this swap with a Festiva so knowledge is limited.
90-94 Mazda Protege DX Engine (B8-ME) - 1.8 liter SOHC 16v (1839cc). Puts out 103hp. Great power all around, but slightly less high end than the DOHC version.
Installation: Same as BP-DE, its the same engine block, but with a different head (i wouldn't be surprised if the head was the same as the SOHC 16v head on the earlier MX3's). MIGHT be able to use the festiva's manifolds on the head, but no one has test fitted them so no one really knows.
Hope this answers all the questions for the next month or so...... Add to it if you'd like :)