The second of two "how-to" articles on turning your BMW 2002 into a BMW 2602 by Pete McHenry from the November 1987 BMWCCA Roundel.
2002 SIX Cylinder Engine Conversion
"It began with a casual conversation, it was a blast to do, and the result is sensational."
We will resume our installation of a BMW small six in a 2002 with the engine-transmission assembly lowered into the chassis. The cylinder head can be temporarily installed with two or three bolts to help with measuring.
The exact location of the engine in the chassis is critical because of some very tight clearances at several places.
Stock 2002 rubber mounts are used on both sides. Use a Bavaria rubber mount under the transmission. It's stiffer than the 2002 unit.
When everything is right the cylinder head cover will miss the fire wall by l/4 inch, the flywheel stone guard will miss the steering track rod by 3/16 inch, and the eight inch diameter front pulley-damper will clear the front sway-bar by 3/8 inch to 1/2 inch with the car's weight on the wheels.
However, if you jack up the front of the car, which allows the suspension to hang free, the sway bar hits the front pulley-damper.
The eight inch diameter damper is used on 320-6 and 325-528 eta engines. The 323 and 325i have nine inch diameter dampers.
In this case we had our 22 mm. front sway bar reworked at a truck spring shop. They put it in a large press and bent a "U" shaped depression in the bar just under the damper- pulley. The offset is 5/8 inch which gives 1/8 inch clearance in the worst situation.
If you have a nine inch damper you may have to make a special sway bar that passes between the pulley and the oil pan, or rework the mounts for the sway bar to drop it further. Some engines have a long front pulley bolt. The extra material should be trimmed off the hex end.
With all this completed and bolted down, you can take your drive shaft to a drive line shop for cutting and balancing. When you reinstall the drive shaft, make sure the shaft operates with no deflection at the center "U" joint or you will have vibration problems. Shim the transmission mounts or center bearing to get it straight.
Cooling is taken care of with an '85 323i radiator. Two round rubber pegs pilot into sockets in the bottom tank, and two strap brackets with rubber under them tie down the top tank. The pegs are made from old Chrysler rear-end snubbers. The rubber snubber has a 5/16 inch threaded stud bonded to it. Drill and tap the front cross member at the appropriate locations; and thread in the snubbers.
Hoses are all European 323 up front. We made up special hoses and lines for the heater. The 323 surge tank bolts to the right fender apron with simple brackets.
An electric fan is in front of the radiator, and is controlled by a temperature switch and relay. A special water pump is used that is only 3 13/16 inch deep including the pulley and fasteners. This reduces the length of the engine almost an inch, and allows everything to fit in a 2002 with no cutting.
By this time you have permanently installed the head and cam drive. The front belt guard must also be European 323 to allow the in close water pump hose to clear the radiator.
Electrical is easy; all the wires that routed across the upper firewall are now on the left fender apron. Relocate your coil to the area where your battery used to be. It is in the trunk, isn't it?
An after-market tach is necessary; unfortunately the 4 cylinder tach doesn't understand what 3 pulses per revolution mean. Various units are available that can be reworked into the dash panel instrument cluster. One wire, the oil pressure sender lead, is on the right side of the engine. We routed it over the top adjacent to the ignition wires. We would like to build a set of headers for this car at a later date; for now, we used two stock cast exhaust manifolds.
One head pipe drops in front of the fire wall, the other must be routed rather twistily past the steering gear idler arm bushings and bracket. These bushings are plastic and need to be kept clear of heat. A heat shield was fabricated that bolts to the frame rail at the outside and is sandwiched between the motor mount and frame on the inside.
We used a Bavaria resonator and a 2002 turbo muffler to finish the system. In any case, some cutting, fitting and welding is necessary.
- Rear view of transmission case and track rod area
- View of cylinder head and fire wall showing heater hoses, vacuum and fuel system pieces
- Rubber pegs for mounting radiator are screwed into front cross member
- Right side overall view
- Left side general view
- Top front view
- View of electric fan installed. Note trimming of upper sheet metal to clear fan blade
- Cylinder head rear showing heater hoses and throttle linkage bracket
- Under side view showing front head-pipe and steering idler bracket
Clutch slave cylinder, or can be done with linkage. The tii bell crank and bracket assembly can be reworked to actuate carburetors quite easily, and bolts to any 2002 fire wall.
We are using a 4-barrel carburetor here using the aforementioned linkage. An electric fuel pump is mounted in the rear, near the tank.
When all this was done, we hit the starter and WOW!, it lives. The only thing that was wrong showed up when the engine started getting hot even though the fan was on. The red wire turned out to be negative -- not positive and the fan was running backwards. Reversing the leads solved the problem.
Some general comments would be in order:
This adventure is best done by a fairly high level shade tree engineer with access to the right equipment. A lot of details like which wire goes where are unsaid here, because these people know about that stuff.
The only disadvantage to this package that I can see is the need to pull the radiator to allow engine movement when doing a clutch or transmission job.
The 15 pound weight difference assumes use of an aluminum flywheel and the Sachs light pressure plate. If you're staying stock add 15-18 pounds.
With the battery in the trunk, you're ahead anyway. Since the engine and transmission is set back, there may not be any added weight on the front wheels at all.
This project began with a casual conversation at Mid-Ohio in 1985. It has been an absolute blast to do. A tremendous impetus comes from the Tarheel Chapter -- there are so many really great BMWs and BMW people here.
Compared to a "built" 4-cylinder engine the six is like night and day. The torque and mid-range power is sensational. With 10:1 compression, a Schrick 292 deg. cam, 30% plus flow increase for the head we estimate power at about 190. All this and the car weighs just a little more than 2300 lbs. Who knows what the future will bring? Perhaps it will have round tail lights and a six-cylinder engine!
Author: Pete McHenry. Member of the Tarheel Chapter and lives in Winston-Salem N.C.