Subaru Engine in a Bus

by Mark Chambers


Disclaimer: Dimensions for bell housing assembly are from a 1600cc Subaru retrofit. I haven't measured yet to see if the distance from the rear of the crank to the rear of the block are the same on the 1800cc. The 2 features which have to match the VW are:

  1. Distance from transaxle locating face of bell housing to clutch disk surface of flywheel. This can be easily measured on a VW engine with flywheel installed.

  2. Concentricity of locating flange (ring) to crankshaft centerline.

(If you make it thru this part, the rest of the project is cake)

Part 1: Fabrication and Machining of Bell Housing

Needed:

  1. Bell housing off of your Subaru engine.
  2. 1/2" aluminum plate as big as a VW bell housing.....$25
  3. Aluminum welding rod....$10 - $20.
  4. A good (aluminum) welder. $Beer (if you bring the rod)
  5. Machinist with CNC mill or manual mill w/rotary table.
  6. A VW engine & transaxle just laying around to fit and measure stuff.

Study the VW 'flange-type' bell housing. Study the Subaru 'bell-type' bell housing. Look at your aluminum plate. Your new bell housing will only be 1-1/4" thick. Visualize what you are going to make. Do this for a long time.....

A. Cutting down the Subaru Bell Housing
(Machining: This is the toughest part)

Detach bell housing from engine. Set aside the steel reinforcement brackets that go from the top of the engine to the bell housing.

Clamp down to mill table with the Subaru side down. Mill until it is .970" thick. I suggest milling from inside out with a 'Hog' style end mill.

B. Layout and Cut Aluminum Plate

Using a transaxle for a template, layout with a marker the general shape of the VW bell housing on 'cereal box' grade cardboard. Leaving the shape round where the 'flats' are won't hurt. I did this for extra strength. Leave material on bottom edge to later match up to the oil pan 'mating surface'. Leave plenty of material around the VW attach hole locations. Mark the hole locations with a marker, then center punch them for reference.

Transfer your cardboard template to the aluminum plate. Saw or torch the plate outside and in. Make sure the inside slightly overlaps inside the bell housing. Drop a flywheel into your assembly and check for clearance with the flywheel centered. Once every thing is lined up, drill and tap a couple of holes at 3:00 and 6:00 for some 10-32 screws to hold plate to bell housing until welding. Consult your welder and he will tell you how much to grind weld chamfers all around. Big chamfer at bottom between Subaru & VW halves of oil pan mating surface. Clean and chamfer elsewhere, per welders instructions.

C. Welding the Assembly

Weld everywhere possible. There is nowhere that too much weld will affect. (This part can't be seen easily when in the vehicle, so don't worry about massive piles of weld). Get maximum penetration across bottom at oil pan mating surface to allow for re-machining this surface. Build up areas around lower hole locations (center punches) as much as possible (full thicknes of assembly). Build up top hole areas to a little more than stock VW thickness. (There went $20 bucks worth of rod)

D. Machining the assembly

The next stap CAN NOT BE OMMITTED because your assembly IS WARPED from welding.

Clamp the assembly to the mill table, Subaru side down. Clamp lightly keeping assembly in a 'free state' (do not distort). Mill the 'plate' side just enough so that most of it cleans up. Now flip over and clamp with plate side down (on fresh machined surface). Mill the Subaru mating surface just enough for 100% cleanup. Surfaces are now parallel again.

Clamp (with Subaru side down) onto a CNC or rotary table. Indicate in center bore. Indicate across oil pan mating surface to line it up. Machine the VW flange (ring) to the same O.D. & I.D. as a VW engine. (Sorry I don't have the diameters handy). Thickness of assembly (not including ring should finish at 1.220". Mill lower edge of assembly to match up with oil pan mating surface.

Hand grind around top bolt holes for mating to steel brackets.

E. Fitting Assembly

Fit assembly to transaxle. Level it and drill some pilot holes at 4 locations. Drill and tap the lower holes for 12mm studs. Drill the top holes to clear 12mm bolts. Attach assembly to engine using 2 drill shanks where dowel pins go. Bolt up. Remove drill shanks and tap holes for 3/8-16 bolts (they are already the right diameter for threading. Now drill thru bell housing only, to clear for 3/8 bolts. Remove assembly for final cleaning. Re-attach with added bolts. Install a new seal immediatly.

Find the steel reinforcement brackets. Heat them up and bend them around to fit new VW hole locations. Weld a 12mm nut to the starter side brackets. Screw in a 12mm stud to right length (see VW engine). Lock with another nut against welded nut. Note: This must be done because you can't access this area later to use a bolt. The other side can use the std. VW bolt. Screw some more studs into lower holes using loctite. Note: 12mm hi-grade all-thread can be purchased at a Bolt & Nut supply store.

If this sounds like a lot of work, it is. If you have to pay a machine shop to do the machining, you are probably better off buying the Kennedy Adapter kit. I'm not trying to discourage anyone but it was easier for me because I have a CNC mill and a friend who welds. If you can find a Kennedy bell housing on a boneyard engine, you can skip this whole step, also.

Any dimensions that I left or you are not sure how to get, please request and I will dig out my notes or head for the garage and measure again.

Next step:....(way easier from here!!).....Modify flywheel. Fabricate pilot bushing retainer.

Disclaimer: I am going to leave out a few actual dimensions on this one...mainly because it's hard to verbally describe a blueprint. Also because I haven't yet checked to see if the 1800 crank bolt pattern is the same as my 1600. (Been too busy trying to figure out the new turbo and fuel injection) All the dimensions for this part are easy to obtain by measuring the your Subaru crank. If anyone needs actual real numbers, I'll get them (I've got to do it eventually). This text is more of a 'procedure' for accomplishing the retrofit.

Once again, the #1 feature that you are dealing with is:

Distance from transaxle locating face of bell housing to clutch disk surface of flywheel. This can be easily measured on a VW engine with flywheel installed.

O.K....you've had all kinds of time to complete the 1st part. You've probably already polished your new bell housing adapter and sent it out to be rainbow anodized. The rest of the adapter isn't as labor or money intensive as the last, howver, a little more machining is involved, so I hope your machinist is not too pissed off after the 'bell housing project'.

Part 2: Modification of Flywheel & Fabrication of Pilot Bushing Retainer

Needed:

  1. Flywheel *
  2. Mild steel plate long enough to span 2 Subaru flywheel bolts opposite each other, at least as thick as your VW flywheel center hub***
  3. Machinist to bore the center of your VW flywheel.
  4. Oilite bronze bushing 3/4 O.D. X 1/2 I.D. X about 3/4 long***

* I used a 200mm 6 volt flywheel. I like the 6 volt starters. Between my 63 & 64 I've gone through 3 starters in 20 years running on 12 volt systems.

*** There may be a simple way around the entire bushing retainer on the 1800cc. The bearing retainer described is needed for the 1600cc.

The VW flywheel locates with 4 dowel pins. It fastens with a 'gland nut'. The Subaru flywheel locates with a 'bore' over a hub on the crank. It fastens with 8 bolts.

You are going to modify the VW flywheel so that it locates over the hub on the crank, and fastens with 8 bolts.

With the VW flywheel on a VW engine, note where the pilot shaft bearing (in the Gland Nut) is in relation to the flywheel clutch surface (your main reference for all of this part). With your new setup you have no Gland nut, no needle bearing. You have to have a bearing or bushing at this 'location'.

You are going to fabricate/machine a 'retainer' to hold a bushing at the position of the current needle bearing.

A. Modifying the Flywheel...the Machining Part

Notice that the Subaru flywheel has a 'flat' face that attaches to the crank. The VW flywheel has a 'flange' for sealing around the outside of the crank, using an o'ring or gasket. This 'flange' has to go away.

Clamp the flywheel to the mill table, resting on some 1-2-3 blocks under the clutch disk surface. The crank side is up. Mill the flange flush with the center surface of the flywheel. Install for dowels into flywheel. Using a dial indicator 'sweep' in the four pins to find 'center' of the flywheel. If they are sloppy, sweep in the center hole of the flywheel. Bore open the hole (not very much) to slip over the hub on the Subaru crank.

The next step should prefferably be done on a milling machine, but can be done manually.

Flip the flywheel over. If still on the mill, indicate in the center bore. Measure the bolt pattern on a Subaru flywheel or the Subaru crank for the 8 bolts. Notice that 2 holes are spaced further apart than the rest. If on the mill, calculate the bolt pattern and drill. Counter bore the holes (big enough for the washers on the Subaru crank bolts) flush with the center surface of the flywheel.

If doing the hole pattern by hand, center the Subaru flywheel over the VW flywheel. You might want make a simple alignment tool thru the center bores. Transfer punch, drill, and counterbore the holes using the Subaru flywheel as a template.

B. Fabrication of Pilot Bushing Retainer...1600cc. (***may be a simpler way 1800cc)

Without showing you a blueprint, all I can do is describe what you need to make. Look at the output shaft on your transaxle. Notice that after the 'bullet' end of the shaft, there is the part of the shaft that runs in the VW gland nut needle bearing. There is more available shaft before you get to the splines. The retainer that you need to fabricate attaches to at least 2 flywheel bolts. It uses the space from within your flywheel almost out to the clutch disk. (Lay the clutch disk in place and see how much space you have). The retainer is bored out for a std. 3/4 bushing. The bushing needs to be bored for a slip fit for the output shaft. The bushing will ride on the shaft back closer to the splines than the original gland nut bearing.

On the 1600 engine, the needle bearing in the end of the crank must be removed. If you can't get it out, use a 5/8 drill, (that you dont mind chewing up a little) to remove it.

The 1800 crank has clearance for the nose of the shaft.

***simpler way...maybe:

The Subaru 1800 flywheel has a 'bearing pressed into it. There probably is a standard metric bearing which has the correct I.D. for the VW output shaft.bearing. I don't think the VW flywheel has enough meat for locating on the crank and retaining a bearing but I will reseach this A.S.A.P.

Install the modified VW flywheel onto the Subaru engine with your rainbow anodized bell housing in place. Measure from the transaxle locating surface to the clutch disk surface and make sure it matches the VW engine you have setting around. If it does, then your ready to bolt up and see if it cranks over.

Next step:....(no more machining!!).....Cooling system side-hinged decklid. fabrication:

Part 3: Cooling system and side hinged decklid fabrication.

Needed:

  1. ***Radiator out of Subaru, or a taller, wider, but not thicker one. $50-75 w/fans
  2. (3) VW bus decklid hinges in good condition.
  3. Welder
  4. (2) 21" full flex radiator hoses, 1-1/4 dia.
  5. 3/4" long cabinet lock or equivalent latch assembly. The locks are nice because they serve as a decklid latch and if you get (2), you can throw a matched one on your gas door.

    From the steel supply store:

  6. 1" Sq. box tubing with 1/16 wall, about 12 feet. $8
  7. A strip of 1/8 x 1-1/2 flat steel bar $8. This will be to make all the bracketry such as latch mount striker plate, and radiator attach brackets.
  8. (4)16 gage sheet metal strips. They will sheer them for you. (2) pieces @ 40" long x 1-1/2" wide, (2) pieces 23" long x 1-1/2" wide. $10
  9. Enough body sheet metal to cover the entire area of decklid and rear apron.
  10. About 6 feet of 1-1/4 round steel tubing with 1/16 wall.
  11. (3) pieces of 1/4 or 3/8 steel, 2" long x 3/4 wide. (hinge mounts)big enough to make lugs
  12. A strip of 3/5 x 1/8 flat steel bar about 11 inches long. You may as well get a long piece...the price for a 12 foot piece at the steel supply will be the same as a 2" piece at the hardware store. $6

Note: This phase requires a lot of fabrication and welding. It will also take a while. (It took me about 10 hours over 2 weeks time)

*** My 64 Double has a '82 Subaru radiator. There is room to go 4" taller and 3" wider. This doesn't sound like much but that is a lot more cooling capacity. The stock radiator is cooling the stock 1600 cc engine fine but I will be upgrading when I add the 1800cc Turbo. If you don't have a radiator, build the decklid frame first, then find the biggest radiator that will fit on the frame.

Study the existing VW bus decklid. Notice how the hinges mount to a flat surface on the bus, and to an angled' surface on the deck lid. You are going to mount (3) of these on the right side of the door opening. (The only 'cutting ' of your vehicle will be the 6 attach holes that you drill for the hinges.) Remove the rear apron. Notice how the opening is straight until it gets to the bottom, then it curves in toward the front. Your new decklid will be made to follow this contour. It will fit the entire area of existing decklid and rear apron. The assembly you will make is as follows:

  1. A box tubing 'frame' that fits inside the opening and has hinges on the right and latch and bullet pin on the left for locking and support. The radiator is also attached to the 'engine compartment' side of the frame.
  2. A skin on the outside with matches/lines up with the back of your bus. It will be flush all around for a nice look. It also has a large cutout to exhaust air from the cooling fans out to the rear of the vehicle. The cooling fans are on the rear of the radiator and don't stick out past the skin.

Measure the door opening and sketch the inside opening and the outside opening. now draw in a rectangular frame inside the opening. 3/8 away from right side of door opening, 1/4 away from top' and 3/4 away from left. For my '64 this framework (1" box tubing) ended up at 35-1/4 wide and 20-3/4 tall. Now with the frame sketched in, shorten the bottom cross piece by 3" on each end. Draw in an angled pieces that joins the sides at 8" up from bottom. This cleared area will allow you to shape the bottom corners of the decklid to match the bus curve at the bottom. Add a 4" long gusset across each top corner for strength and to kit assembly square. Cut all your pieces, and chamfer them for welding. I would recommend tacking the whole thing together and checking the fit (right, left, top clearances listed above). Weld it all over and straighten.

Look at the right end of frame and right side of door opening. The hinge locations down from the top of the frame will be 2-1/2", 7", and 11-1/2" to the center of each hinge. Cut the right side box tubing at these locations so that you can weld in the (3/4 x 2") steel lugs at an angle. (Look at the mounting angle on your old decklid). Weld them in a grind any weld off the faces. Clamp all 3 hinges onto a straight edge for alignment and layout screw hole locations in the lugs. Pay attention to which way the hinges go...they can be put on backwards and won't work. If you have metric taps, drill & tap mounting holes for existing screws. If not use 1/4-20 flat head screws. Attach the top 2 hinges.

Modify the lower hinge. Weld another 3/8 on so that it will reach. Fill the holes with weld and grind and re-drill holes at the same distance from edge as other hinges. Re-attach to frame.

Cut a piece of the 3/4 x 1/8 flat bar to 11" long. Center along all 3 (attached) hinges and transfer the hole locations to the center of the bar. Center the holes more or less along center of strip as best you can. Drill and tap for 1/4-20. This is a long nut plate which will go between the right taillight housing and the right door frame.

Now fit the frame with hinges to the vehicle. Don't worry to much about top and left spacing. You need to mount the frame so that it is 1/16 below flush with all bus body metal. Have someone hold it while you mark the hole locations. Drill thru the bus right door frame for 1/4 bolt clearance. Use a 5/16 drill. Hold the 11" nut plate behind the frame and see if the holes line up. If they do mount the decklid with 1-1/2 long 1/4-20 flat head screws.

Find a 3/8 or 7/16 bolt that you can cut up (about and inch long). Grind a rounded bullet type end on one end. On the other end grind a large flat along about half the part and thru about 1/3 of the diameter. Fit this pin against the left side frame about halfway down. This will be a 'support pin' to hold half the weight of the decklid. Don't weld it on yet.

Make a 'striker plate' about 1-1/2 x 1-1/2 x 3/16 and fasten it behind the bus left side door seating surface. (The surface the door will close against) Use flathead 1/4-20 screws from the front.(They will be covered with rubber trim). Swing the decklid closed holding the bullet pin in place, center the pin to the plate and weld it on. Grind away any weld on the bullet side. Mark a hole location for the bullet pin to go thru the striker plate, and drill. Make sure the frame is level, even if you have to pick it up a little bit. This pin sets your alignment for the whole thing. For you latch, weld a 2" x 2" plate flush with the outer (skin side) of the frame. Locate it so that it 'latches' on the striker plate.

Radiator mounting:

On the top and bottom frame of your radiator should be plenty of holes. Some of them will be threaded. I built (4) brackets, 2 top, 2 bottom, and attached them to the radiator. Then I welded 4 'standoffs' (1" box tubing...about 4" long) to the top and bottom rail of decklid frame. I then pinned the brackets and radiator to the frame with clevis pins for quick removal/service.

Note: Make sure the fans do not stick out past rear of frame.

Upper hose runs to the right thru 1-1/4 steel tubing, then a full-flex hose into engine compartment. (I'll discuss more of plumbing on the engine side later). Lower hose runs to a brace (to protect from wear & tear on soldered hose fitting at bottom of radiator. Then a 18" full flex hose to the water pump. The upper hose floats into the battery compartment against the battery when door is closed. Lower hose feeds itself forward next to the valve covers.

Adding the body metal:

Close the door and latch. Take the 1-1/2 wide 18 gage strips and frame the door leaving about 1/8 inch all around. Tack weld into place. Where the sides come down bend strips to follow body contour all the way to the bottom. Add a piece across the bottom and bend in to meet sides. Some custom snipping will be in order here. Once everything fits smoothly add welds every couple of inches. Grind flush on the outside.

Cut the body sheetmetal 'skin' to 1/2" bigger than your frame all around. Layout the large hole(s) for the fans to exhaust thru. Fit the skin and fold over all edges carefully and crease. Mine needed no welding.

Add some wire mesh or whatever suits you to finish the look of the decklid. One note: I tried 1/4" raised expanded metal first, but it created a lot of interference for the fans. I switched to some 1/4" square wire mesh. I sprayed my fans and that side of the radiator flat black to help hide hardware.

License plate was relocated with a simple metal bracket coming off the right taillight bottom screw.

Next step:....All the Mickey mouse stuff that goes with the retrofit. Plumbing, electrical, ignition, exhaust, gages, etc....



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