A two-part "how-to" on turning your BMW 2002 into a BMW 2602 by Pete McHenry from the November 1987 BMWCCA Roundel.
2002 SIX Cylinder Engine Conversion
When six gozinta four, good things happen to your Bimmer.
Let's take your much loved BMW 2002 and make use of BMW's latest small engine technology. How about 2.7 liters with only 15 pounds more weight than a tii engine: and with the use of lots of your old parts?
Interested? Read on, we are going to go through the steps via sketch, photo and word of how to install a small BMW six in a 2002. There will be no cutting or butchering of your favorite and most loved bodywork.
These engines have been built in various displacements from 2.0 liters to 2.7 liters. The particular engine we are using here has an 84.4 mm. bore and a 76.8 mm. stroke for 2579 cc.
Cylinder heads have 40 mm. intake and 34 mm. exhaust valves in the small port variety: 42 mm. and 36 mm. respectively are used in the 325i big port version. ETA engines use the small port type and make use of only 4 of the 7 cam bearings. After-market and other factory cams use all seven: be sure to drill the extra oil feed holes for the other three bearings if you use the ETA head with one of these cams. Lots of engine mods are possible, but this article is not going into that area.
As you can see in the drawing the reason the six fits is because the four is pushed forward to accommodate the distributor location. Since the six has the ignition on the left side, the engine can be moved back a lot. The front of the engine ends up at the same location as the four.
The best used engine to buy for this conversion is a BMW 325 version with the front sump aluminum oil pan. This pan fits the 2002 chassis perfectly.
With your engine in hand, let's start putting the pieces together. We are using a 4 speed transmission here, very simple; low cost. You will need a '78-79 320i U.S.A. 4 speed box. This unit is identified by the two bolt heads on the left side of the case and back cover which hold the reverse gear shaft and shift levers in place. Also there is an Allen Head screw on top of the rear cover. This trans has the wide first gear teeth to handle the torque of the six. Buy a 323 European 4 speed trans case, PN-23-11-1-206-940; most direct importers can get this for you. (About $180.00) any BMW trans shop can switch cases for you. All other parts are the same. Use your 2002 flywheel (228 mm. clutch, please).
Clutch actuation uses a 320 slave cylinder with the standard throw-out yoke and retainer spring. Use release bearing #21-51-1-204-525 as used with any 320 with a 228 mm. clutch. You can use special heavy duty Sachs clutches, but use at least a tii pressure plate. You will find that the stock 28mm. long flywheel bolts are too short. BMW has a new 50 mm. bolt for the ETA engine with the double mass fly wheel. Cut these to suit, about 34 mm. A short steel hydraulic line (N.A.P.A. 813-1261) is used along with BMW hose PN-21-52-1-153-512 to hook up to the 2002 clutch master cylinder. The cylinder end of the hose has to be reshaped slightly.
Cut off the small lug on the left side of the trans case just behind and below the starter; it has a 10 mm. hole drilled through it which will help you identify. Your 2002 starter will work fine with a 3/16 spacer ring under the mounting flange. This pulls the starter back just enough to prevent dragging the starter pinion on the ring gear.
If you have an ETA engine, you must get a European 320/6-323 distributor. The Motronics unit won't clear the radiator. Distributor PN, 12-11-1-360-659 has breaker points and is the lowest cost. If you got an alternator with your engine, fine, but the 2002 unit will work also with a simple bracket.
The transmission shifter rod and bracket are shortened 88.4 mm.; a simple cut and weld operation. The 325 engines with the aluminum oil pan have an anti-vibration bracket that bolts to the block and lower trans case. This is a nice item to use: however it hits the steering track rod. We cut the two sides off of the casting and made up two brackets; right and left, not unlike the stock 2002 vibration stiffener. The 2002 flywheel stone guard was reworked to fit with these other pieces.
- View of ETA engine cylinder head. Note oil holes beside head bolt holes for bearings 1, 3, & 5. Drill the other three locations for 7 bearing camshafts
- View of engine compartment showing left mount stiffener and relocated biscuit on right side
- Transmission tunnel recontouring and rubber new rear mount
- 6 cylinder transmission (left) '79 321 transmission (right)
- 4 speed Getrag transmission with hydraulic lines for 2002, note bolt heads on side of case (below slave cylinder) and rear cover. These denote late 4 speed with H.D. gear set.
- Small 6 with 325 oil pan right side mount, two "front" manifolds and our special short water pump
- Small 6 head on it leans right 23 degrees, instead of 30 degrees
The motor mounts are pretty simple. We use the existing 2002 biscuit on the right. The hole center lines are moved to the right 19 mm. and forward 3 mm. The snubber bracket underneath has to be ground along one side to line up with the new holes.
Since many 2002 left motor mount arms have cracked in service, we felt some reinforcement was in order. A special reinforcing plate was fabricated to triangulate the structure.
The transmission tunnel must be massaged with a large flat face hammer to clear the clutch slave cylinder on the left, and the bell housing portion of the transmission on the right. Let's make the new rear mounts first which will simplify the massaging operation.
The new mounts are made of .093 x 1l/2 inch steel strip, and approximate the shape of the originals. They are on the same plane, but are set back 88.4 mm. We used three bolts to hold them in place. Two 6 mm. on the bottom and one 8 mm. on the top.
Install the transmission cross member on these mounts: elevate the transmission only into approximate position. At this point you will see where the tunnel has to be "re-contoured" with an appropriate hammer. You will not notice the results of this massaging inside the car.
At this point you've got some time to clean and detail the under hood area of your car. The engine, if apart, might best be left with the cylinder head off: it's easier to install without it in place.
Our next installment will cover engine side mounts, cooling, chassis electrical, exhaust, throttle linkage, drive-shaft, and other miscellaneous steps.
About the Author: Pete McHenry is a member of the Tarheel Chapter and lives in Winston-Salem N.C.