I actually purchased and received the 5-speed adapter kit from Rivergate several months ago and I have had the gearbox for several years. Although the car has been ready for a while, other projects have kept me from preparing and installing it. In addition to the basic adapter, I also purchased the two options they supply. The first is a custom slave cylinder that includes a braided hose directly to the master cylinder. The Sprite slave could have been used but this one is supposed to give better feel and it greatly simplifies the plumbing. The second option is a speedometer cable that mates to both ends without modification and includes a gear set matched to my rolling tire diameter so the speed reading is correct.
The Model A chassis is pretty well done and waiting for wheels to return from the powder coater and new tires to arrive from Lucas so Dan ran out of work temporarily and started on the Sprite 5-speed setup. This is where we are after a couple of days. The modifications to the gearbox are done and the adapter is installed, replacing the original steel back plate on the motor. I had to grind clearance for the oil pump cover in the rim of the bell housing. See the crescent shape cutout in the upper right of the left photo. Also had to cut out clearance for the slave cylinder. Lower right in the same photo. Finally it needed a large hole cut through for the Lucas starter bendix. Lower left in the photo. That is the new clutch release bearing installed. The adapter plate, itself, did not require any modifications although I did polish the edges just for looks. There is a liberal amount of silicone in various places between the motor and the plate, some of which was a little tricky to apply.
A couple of days later we finished fitting the adapter and gearbox to the motor and here it is ready for test fitting into the car. So, naturally, we tried it. Actually, it was probably closer than I expected, based on all the stories I have heard. It went over the radiator horns without too much effort then we tilted the rear down severely to begin entry into the tunnel. Again, no real problems surfaced but it stopped about an inch short of lining up with the motor mounts. At that point, the rear mount was hard against the rear cross member while the bell housing was against the heater plenum and the oil pan was a good quarter inch short of clearing the front cross member with zero clearance.
The only viable option was to pull it back out to grind about an eighth of an inch extra clearance from the back of the bell housing and to grind the upper bolt of the slave cylinder that would eventually interfere with the frame rail as the instructions suggested. These photos show the back of the bell housing before and after that additional grinding. That was Friday. First thing Monday, we tried again. this time it got a little closer but still the crackshaft pulley would not quite clear the front cross member. Again we pulled it out and did more grinding in that same spot for the same reason. This time, I produced a tiny through hole that I patched with a thin coat of JB Weld applied like bondo. On the third attempt, it went in although I did have to give it a good shove from the front to finally get past the cross member.
The last step on installation was to install the lower section of the two-piece rear mount. The upper section is bolted to the tail of the gearbox before installation since that would be inside the tunnel and unreachable later. The lower section is added after installation and bolted to the cross member from below then to vertical extensions through the tunnel from inside the car. Finally, the two sections are mated by extensions outside the tunnel. There was an unexpected problem with this method as described in the supplier's instructions. It seems that the supplier of the mount changed the design a little without notice. This made the upper plate wider at the front that at the back. In fact, it was wider than the space between the vertical extensions of the lower plate, making it impossible to slide it in from the front. We had to pull the whole installation back out a few inches to allow the lower section to be inserted from behind then slid back to the front. Since the displacement put the pulley back above the front cross member, it was too tight to fit back in. Again, some extra force was required but once back in place. The camera angle exagerates it a little but the first photo below gives a pretty good idea of the design flaw. Dan finished the rear mount installation and we ended another busy day. We did scratch a little paint at the front and rear cross members and the heater shelf which I touched up with a brush. These photos show the final installation.
In the left photo, you can barely see the final clearance between the bell housing and the heater box if you look really closely. The right photo shows the last remaining issue with the installation. The rear mount raises the tail shaft just enough to make the U-joint tap the top of the tunnel at one point in its rotation. This is not an unexpected problem. In fact, there are several known solutions. One popular one is, With the car on jack stands and engine running in gear, toss a broomstick into the tunnel so the U-joint catches and beats it against the tunnel from inside, making clearance. I admit, I am not brave enough to do that. Instead, I worked on it with a crowbar, using leverage off the U-joint until I got about 1/4 inch clearance. I hope that is enough. Time will tell.
Meanwhile, I wanted to ensure that everything else fit properly so I began temporarily installing all the stuff that attaches to the motor. I don't have a manifold gasket yet and the sources are all shut down due to the corona virus so this will all have to come back off.