FE3 Miata Swap: Big Block Roadster

If Mazda offered an engine upgrade option in 1990 for their new roadster, the FE3 would have been a perfect fit.

Upgrade
The basic principle behind the swap was to create what might have been a factory offered engine upgrade when the car was new. The 1990 Miata’s B6 1.6 liter was rated at 116hp and 100ftlbs torque. The FE-dohc (FE3) from the same era was rated at 145hp and 145ftlbs at a similar compression ratio.
BP and FE3 Comparison (courtesy Egonn)


Size
The FE3 is physically larger than the B6 (and BP). Measurements below were taken from the bottom edge of the block to the top edge of the cylinder head for height, and from the front and rear of the block for length. Various published weights of the BP show the FE3 to be around 50 lbs. heavier than the BP.  The FE3 has a bore and stroke of 86mm x 86mm. Displacement is 1998cc, and it has a cast iron block and aluminum head.

Performance Potential
In stock form, the FE3 has great potential under boost because of it’s larger size – more strength and flow. It’s larger in every way compared to the BP and B6; crank, block, rods, ports, valves and cylinders. The FE3 is essentially a scaled enlargement of the BP and B6. Anyone familiar working on the BP and B6 would be right at home working on the FE3.

Mazda FE3 (FE-dohc) 3/4 view on engine stand

Exhaust port spacing- BP exhaust manifold top, FE3 bottom

Rod comparison- FE3 left, BP/B6 right