Weekend update

A lot has happened over the past week. (It’s been a quiet week in Lake Wobegon. Not.)

The cool part, at least visually, is that the big engine has been temporarily bolted into the car. This was done to check the clearances around the engine and the connections of the various hoses, linkages, wiring, etc.

Photos here.

There is not much room available! The engine sits back in close proximity to the firewall. The heater hoses and expansion tank hoses will be tight between the back of the engine and the firewall.

The passenger side of the engine has adequate room. The exhaust manifold on this side will probably not need to be modified. The new down pipe can be bolted directly to the manifold flange. The air conditioning compressor may need some adjustment to fit between the engine block and the frame.

The front of the engine will be tight when the radiator is installed. The radiator hoses will need to make some sharp turns. We had purchased an air filter box from an 840, but the installation is not obvious at this point. Not a big deal. We will work through this.

The driver’s side of the engine presents some real challenges, however. There is a lot of equipment to be squeezed into the space. The steering column has priority. It takes a straight shot from the steering wheel through the firewall and down to the steering rack. We had installed a Z3 steering rack a couple of years ago to provide a quicker steering ratio.

Also on the driver’s side is the brake system. The master cylinder and brake booster will be relocated from the firewall, due to lack of space there. The wide V8 engine takes up the face of the firewall. There is an option to mount the cylinder and booster at the front, just behind the headlights. On our car, a block that is the anti-lock brake controller takes this space. We are searching for a smaller booster to save some space. We are also designing a new linkage to transmit force from the brake pedal to the booster. There is much work to be done, although imagining a solution may be more difficult than fabricating it.

The transmission mount appears perfect. The new transmission is the same size as the original. The shift linkage has been cut to fit. We want the new shifter in exactly the same location in the car. The engine mounts we ordered from Germany appear to be perfect, as well.

We have a new differential, too. The original gear ratio was something like 4.10 to 1. This would not work for the new engine. In fact, it would mean the first two transmission gears would be useless. The new engine has so much torque that it would rev through the first two gears too quickly and probably melt the rear tires in the process. The engine would be screaming at highway speeds. Our five-speed transmission does not have an overdrive gear. The new differential came from an old BMW 325es. These cars were built with engines that were made to run at a lower speed. Therefore, the differential gear ratio is 2.93 to 1 (or 2.73, depending on date of manufacture). Limited slip, of course. This will allow us to use all five speeds of the transmission. The calculations show that the car should be doing 60 mph in second gear -- in less than 5 seconds. You don’t want to know what the calculated top speed in fifth gear is.