Below are some lessons learned from engine, transmission, driveshaft, differential, and rear axle preliminary placement. If anyone notices I am doing something wrong, I would certainly appreciate the input.
1) 16” had to be removed from the middle of cross-member C to place the engine into the frame. This will be tied back together with a piece that will be bolted in place for ease of removal in the future.
2) For the engine to fit under bonnet, the oil pan had to be 2” below the frame. This equates to 3” ground clearance with the front lower control arms level. This also means the engine mounts will have to be made to extend below frame members G1and G2. The ground clearance will be improved, if needed, by adjusting the shocks to raise the frame.
3) For the engine throttle cam to fit under the bonnet, ¾” of fiberglass will have to be added to the underneath of the nosepiece purchased from Jack at Kinetic Vehicles.
4) For the engine to fit and the location of the gearshift lever to be reachable, the engine had to go as far back as possible, the transmission case coming within ½” of frame cross-member Q.
5) With the differential and rear wheels centered on the frame, the driveshaft connection to the differential is off to starboard about an inch. Design of the Miata, I guess. The driveshaft output from the transmission is exactly centered in the vehicle.
6) To obtain the 3 degree downward slope of the driveshaft, the rear wheels had to be 9/16” lower than the front wheels (which in reality means the frame in the rear will be 9/16” higher than the frame in the front, which will give the car a slight downward slant). Most cars are more pleasing to the sight with a slight rake forward like this and perhaps more rake will be added by adjusting the rear shocks.
7) An attempt will be made to use the heavy aluminum rail that the Miata used to tie the transmission to the differential. Approximately 11 ½” will have to be removed from the middle of the rail. An attempt will be made to bolt the resultant pieces together after shortening.
The resultant location of the rear lower control arms means that frame members RU1, RU2, and Z will have to be removed. Bracing for mounting the differential and rear lower and upper control arms will need to compensate for these removed members.
9) For the rear shock absorbers to mount on the upper plates of the frame and the lower control arm and still remain vertical, they will have to be mounted forward of the rear axles by 2”.
10) The rear upper and lower control arms and mounting locations will be designed to be as close to the Miata dimensions as possible. This means the inboard mounting locations for the rear lower control arms will be slightly below the frame.
11) With the face of the drive shaft mounting plate on the rear differential vertical, the mounting bushings on the heavy aluminum wishbone cross-member that fix the differential on top have a slight forward tilt. I surmise it is more important to keep the driveshaft mounting flange vertical so I will have to tilt the mounting hardware for the wishbone accordingly.