The Swap

Warning/Disclaimer. This information is not guaranteed to be complete or accurate. If you attempt this swap Cork Sport is in no way responsible or to be held liable for any information or advice given.

The 1st gen 323 GTX (BF platform) comes with a B series 1.6 DOHC turbo motor refered to as the B6T. In mid 1989 Mazda built the "2nd" generation of the 323 GTX from the newer 323/Familia platform. The 2nd gen GTX (BG platform) came with a 185hp 1.8 DOHC turbo motor called the BPT. The 2 motors use the same basic block but the 1.8 BPT is physically longer than the B6T. They both share the same bellhouse pattern making this swap feasable from that standpoint. There are alot of difficulties in installing the BPT into a BF GTX. Since the motor is longer it moves all the pullies and accessories very close to the passenger side frame rail. The passenger side motor mount also needs to be modified. Since the block is a little different the axle shaft that bolts to the back side of the motor no longer fits correctly. The BPT has the same bellhouse pattern on the block but that is it. None of the the other oil pan or transmission bolts will line up. The power steering pump bracket bolts up but the pump will not fit due to the different design of the exhaust manifold. The intake on the BPT is aimed to the drivers side of the engine bay instead of over the valve cover like the B6T motor. The BPT turbo has a different 4 bolt flange instead of the 3 bolt like the B6T on the turbo outlet flange. The list continues about the differences and they will all be addressed. in this section.

Electrical

The GTX is currently running the B6T ECU, injectors, sensors, everything. The were a few exceptions. One was the TP sensor. We had to splice in the connector for the BPT throttle body TP sensor. At a later point we will be using the low resistance BPT injectors but we will have to add resistor packs to compensate for the B6T ECU. There is currently 1 sensor that is not being used. The BAC valve is located on the passenger side of the intake manifold on the B6T motor. The BPT motor has the BAC bolted directly onto the botom of the throttle body. Since the throttle body is pointed towards the drivers side of the car it makes the connection a little difficult. We will be connecting it at a later point.

Here is the BAC valve plug.

Here is the BAC valve on the throttle body.

Motor Mounts

The mounting of the engine into the GTX is not that difficult. The B6T transmission has 3 of the mounted bolt to it. The only mount that needs to be modified is the passenger side motor mount bracket that bolts to the frame rail. The back was cut out of the bracket to allow for the motor mount bolt hole to be re-drilled. If the bracket is not cut out the motor mount won't have enough space. The B6T motor mount bracket that bolts to the engine and motor mount was used to get the correct fitment and alingment.

Axles

The axles are a problem when swapping motors. The stub shaft for the right front axle is longer than the BP part. This causes the holes no to line up and be able to bolt onto the engine block.

To solve this you will need to build a bracket so both bolts tighten down and hold the support bearing to the engine block. The Only way to get the 3rd bolt in would be to drill the bracket itself. You will also need to grind down the top edge of the bearing support or it will come in contact with the oil cooler.

Engine/Transmission

Bolting the engine shows the only real downside with this swap. The BP motor and the B6T transmission share the same common bolt pattern but there are a few differences. The bottom of the transmission and the engine oil pan bolt together. The B6T and the BPT have the bolts in different spots. The BPT oil pan extends down futher as well.

Clutch

We used the flywheel and clutch assembly from the B6T motor since it bolts right up to the BPT motor and matches the transmission.

Intercooler

This is where the swap gone interesting. Since the piping had to be run different we decided to install a larger intercooler into the car. We used the best qualtiy core we could find for the job. We started with an Apexi core designed for the Nissan Skyline. The core measures 24x11x3. It was a difficult fit and trimming of the sheet metal was required.

Since we installed such a large intercooler we decided in needed more airflow. We installed a Japanese spec bumper. The bumper is very functional with much better airflow for the intercooler and the radiator.