When I bought my 84 Westy for a song in May 1996, the engine was blown and unrebuildable. I upgraded to a 2.1 and have had very good reliability in the past 66k miles (been on the road since July 1997). A little extra power and torque and it's been a joy to drive. But to do it, a few areas have to be slightly modified or adapted. I made a post to the Vanagon Mailing List in 1996 on this and here's a step-by-step how to:

The first thing to do before setting out to do this conversion is to obtain the Bentley Factory Workshop Manual as it is an invaluable tool in comparing the differences and nuances of both engine types.

This guide is for installing a 2.1 (86-91) engine into a 83.5 to 85 Vanagon originally equipped with the 1.9 engine.

ADVANTAGES:
1. About a 10 to 15 HP gain.
2. About 12 more foot/pounds of torque.

ITEMS NEEDED:
1. Your old 1.9 engine complete - you will need many of the components off of this engine to transfer to the 2.1 engine.
2. A 2.1 longblock engine, either good used (good luck) or a fresh rebuilt (AVP in Sacramento is recommended).
**NOTE: If you do get a rebuilt, be sure that you get either a flywheel (MT) or flex plate (AT) as appropriate for your original setup. If getting used and have to switch over, have a good, qualified machine shop remove and reinstall the appropriate piece(s) and check/adjust the crankshaft end play - replace the Main Seal and O-Ring while your at it as well.
3. Center Air Plenum from a 2.1 engine.
4. Both left and right Air Intake Runners from a 2.1 engine.
**NOTES (Items 3 and 4 above):  This insures that the plenum attaches properly to the 2.1 crankcase and that proper sized intake runners attach with the 2.1 intake hoses.  HOWEVER - Very late 85 1.9 engines were using the 2.1 style plenum using the slightly smaller diameter hoses and intake air runners - you can use this style plenum/runner setup on the 2.1 - so ignore the modifications mentioned below if you're using these.
5. 80C Thermostat and Thermostat O-Ring (VW# 034-121-119). Volkswagen themselves only carry 87c Thermostats, but you can get OE German 80c Thermostats from Bus Depot and others that deal in Vanagon engine parts..
6. New German Water Pump for the 1.9 application (explained further down).
7. Prestone 5/100 Coolant or Texaco Havoline Dex-Cool (Posphate Free) (System takes 18.5 quarts of 50/50 mix of water/coolant)
8. Appropriate support for the transmission (VW 785/1B) as shown in the Bentley Book. VW wants a ridiculously high price for this simple tool, so I had a friend good with welding make one up for me.
9. Good quality jack stands (2).
10. Floor jack.
11. Appropriate tools.
12. Numbered "sticky" tags for hose and wire connection identification. Some electronic shops have these (I happened to get these from the flea market from a shop that went belly-up).
13. VW# 025-198-009/B Engine Gasket Set. A lot of these gaskets you probably won't need if the long block (used or rebuilt) is ready for assembly. But save the stash anyway for possible future use.
14. VW# N901316.02 Exhaust Flange Gasket - 2 each (connects the front/rear header pipes to the collector pipe - they don't include enough of these in the gasket set). OR - you can (and I have) use the VW# 111-251-261B Exhaust Flange Gasket(s) used on a 36HP-1600 Air Cooled Engine.  These are metal on both sides.  The exhaust port hole is smaller, but so slightly that it makes no difference in performance (or breathability) that I've ever noticed and I've used both on the same engine.  Besides, these are less expensive on the wallet.
15. VW# 025-251-509 Exhaust Flange Gasket - As needed (connects the collector pipe to the Catalytic Converter and the Converter to the Muffler).
16. Bosch# 11025 Oxygen (O2) Sensor - Universal 1 wire type. If your's is VERY recently replaced, use that instead and save about $35.
17. VW# N90128703 Coolant Hose - These small hoses are between the Thermostat Housing and Left Cylinder Head and on the Lower Coolant Crossover Pipe between the Water Pump and the Right Cylinder Coolant Jacket.
NOTE:  3/4 Inch ID Hose (Gates or Goodyear Brands) can be substituted.  Most places sell it by the foot, so get a foot of it, cut what you need and stash the balance for a rainy day.
18. VW# 070-115-561 Oil Filter - Best to stick with OE Mann or Mahle.
19. VW# 022-133-073A Throttle Body to Plenum Seal
20. VW# N90305201 Intake Runner Connecting Hose/Sleeves (You'll need 4)
NOTE:  If you're using the smaller intake runners as described above, order VW# 039-133-241 (Again 4 of them).

PRE - ENGINE REMOVAL

Using Bentley as your guide do the following additional things:
1. Disconnect Battery Ground Strap
2. Remove Air Cleaner/Air Box Assembly and Elbow along with all hoses attached (draw a diagram).
3. Follow this sequence with the tag numbers I used:
Tag #1 Disconnect Alternator Harness at Alternator
Tag #2 Disconnect Injector Connection Cyl #1
Tag #3 Disconnect Injector Connection Cyl #2
Tag #4 Disconnect Connectors at Throttle Valve Switch
Tag #5 Disconnect Connectors at Auto Trans Switch next to Throttle Valve Switch
Tag #6 Disconnect Plug at Aux Air Valve
Tag #7 Disconnect Hose at Top of Charcoal Filter Valve
Tag #8 Disconnect Hose at Bottom of Charcoal Filter Valve
Tag #9 Disconnect & Plug Incoming Fuel Hose at Pressure Regulator
Tag #10 Disconnect & Plug Return Fuel Hose at Tee just under Air Plenum
(Note: Very hard to get to - may have to temporarily remove distributor)

AUTOMATICS: Remove Circlip and Spring from Accelerator Rod at Throttle Assy. Put them in a marked baggie and don't lose them.

MANUAL TRANS: Disconnect Accelerator Cable.
Tag #11 Disconnect Injector Connection Cyl #3
Tag #12 Disconnect Injector Connection Cyl #4
Tag #13 Disconnect Oxygen Sensor Plug
Tag #14 Disconnect Ignition Harness at Distributor & Ground on Alternator
Tag #15 Disconnect & Remove Coil Wire at both Coil and Distributor
Tag #16 Disconnect Oil Pressure Harness Plug (Top of Engine)
Tag #17 Disconnect Water Temp Sensor Plug
Tag #18 Disconnect ECU Temp Sensor Plug (Next to Water Temp Sensor)
Tag #19 Disconnect Expansion Tank Sensor Plug
Tag #20 Disconnect Ground Wires and Strap from Ground Tree on Engine Case
Tag #21 Disconnect Plug at Vacuum Switch at Front Right Side of Access Hole

4. If equipped with A/C:
Tag #22 Disconnect AC Compressor Wire Plug
Keeping the AC lines connected, remove the Compressor and Bracket off of the engine and using something like wire and a support to keep the unit clear of the engine (hanging there)

OR

If your AC system is trashed (like mine was):
Disconnect AC Compressor Hoses
Remove AC Compressor and Mounting Bracket Completely

OK That's all the tagging I did.

5. Here was the order of things I did, again using the Bentley Book as a guide:

Remove Muffler and Catalytic Converter from Left Collector Pipe. Leave the Collector Pipe attached to the Front/Rear Header Pipes.

Disconnect & Plug Coolant Hoses from Block and Water Pump. Keep a drain pan handy, there's coolant all over the place if you don't

Disconnect & Plug Heater Supply & Return Hoses at Front Right Side of Engine

Remove Cap from Expansion Tank

Remove the Engine Tin pieces that are directly under the Pushrod Tubes, between the Heads and the Case

With Drain Pan, Remove Coolant Drain Plugs from Cylinder Heads and drain coolant and properly dispose of it.

Disconnect Brake Servo Vacuum Hose at One-Way Valve

Disconnect & Remove Coolant Bypass Hose (8mm) from Heater Return Pipe & Coolant Bleeder Connector. Be careful, the Bleeder Connector housing is plastic and breaks easily (it did on me - cost about $42 from VW to replace), so take a single edge razor and slit the hose to take it off easily.

Disconnect & Remove Heater Return Hose from Crosspipe and Expansion Tank Connector Piece

Disconnect & Remove Coolant Hose Between Block and Expansion Tank Connector

Remove Coolant Expansion Tank

Remove Upper Engine Mounting Bolts and Nuts from Transmission

AUTOMATICS: Remove Torque Converter Bolts through hole on top Center Left of Engine Case (Rotate engine to access each one) (Note: There are 3 bolts - 13mm Hex - use a Socket with a 1 1/2" extension - pretty tight in there because the Air Plenum is in the way.) TIP: Take a small bottle of White Paint and a small Paint Brush. When you have the first converter bolt lined up with the hole take and put a paint mark on the exposed converter fan blade DIRECTLY in line with the Center Line of the Engine Case - put a mark on the trans mating flange too. When you rotate the engine to the next bolt, put another paint mark on the fan blade again and so on. Makes it easier to locate the flex plate to the converter when bolting back in.

Raise Rear of Westy and support on jackstands. Must be at least 12 to 15 inches in the air so that the Intake System and the Alternator can clear (You can remove Alternator if you like). Be sure to chock the front tires to prevent rolling.

Disconnect Starter Wires

AUTOMATICS: Remove Accelerator Rod from Transmission

Remove Outer Engine Heatshield Tin on each side of engine mounted on the Body/Frame

Remove Bolts from Rear Engine Heatshield Tin, but do not remove tin itself

Loosen Thru-Bolt and Nut on Front Transmission Mount so that trans/engine can rotate down

AUTOMATICS: Place support bar approximately 5 inches from the bottom of the final drive housing, NOT THE AUTO TRANS PAN!

MANUAL TRANS: Place support bar approximately 5 inches from the bottom of the final drive housing area

Place floor jack pad on bottom of engine

Remove Engine Carrier Bolts on each end of the carrier where it meets the vehicle frame

Lower engine and trans until trans rests on the support. (Note: Be sure that Oil Filler clears when lowering and watch the wire harness too)

Remove Lower Engine Mounting Bolts & Nuts to the Transmission

Remove Engine from Trans/Torque Converter and carefully lower out and from underneath rear of vehicle.

OK, now we have both engines out on the floor, ready to swap the stuff.

GASKET SEALER: I use Curil K2. It's factory stuff and in my opinion, the best.

ANTI-SIEZE: I use Loctite/Permatex's Spray Anti-Sieze. Use it on every nut and bolt where possible.

HARDWARE: Most places that took nuts, I used self-locking "Fuji" nuts, in particular to the Exhaust Pipes. If you're unable to find the "Fuji" nuts, "Clevelock" nuts work just as well. I have used both styles of these for years on my Air Cooleds and with the Anti-Sieze, they seem to last forever. I'm sure Stainless stuff is better, but real hard to find in good quality and in some (but not all) cases can be pricey. Do what you think is best.

Take some polaroid shots of the old engine assembly in areas you don't feel comfortable in remembering where what goes where.

To be perfectly honest, I don't remember the exact sequence of old engine disassembly, but here are a few notes:

1. Remove the entire Fuel Injection Assembly as a unit - it's easier this way. The Heater Return Pipe will be attached, so leave it on there until we get to that.
2. Remove the entire Rear Carrier Mount Assembly and Heat Shield
NOTE: Inspect the Rubber Mounts and replace if necessary (had to replace the outers on mine).
3. Remove the Thermostat Cover and Housing from the Water Pump. Toss the Thermostat.
4. Remove the exhaust system in this order:
Remove Left Collector Pipe from the Front/Rear Header Pipes
Remove the Front Header Pipe (FIF)
Remove the Rear Header Pipe (RIR)(This is the pulley side)
NOTE: Take note of the support brackets throughout the system and how they attach. Take a couple of Polaroids of how they are mounted so you can put them back the correct way. These brackets are needed, so don't throw 'em away.

I took my sweet time in reassembling, and I didn't write it down, but here are a few notes:

CRANKSHAFT PULLEY:
Models that have A/C and/or Power Steering came with a hefty 3 grooved pulley. If your new engine doesn't have a pulley, you're going to have to swap it over. This requires a shop with the proper tools to lock the flywheel or Automatic Flexplate. Locking a flywheel isn't hard to do, but the proper tool for locking a flex plate is mandatory, because bending one of those with an improper tool will render it useless because they are fragile and expensive to replace. 3 grooved pulleys are torqued at 258 foot/pounds, just like the Flywheel Gland Nut on their distant 1600 cousins. If you have a single grooved pulley, these are only torqued at 43 foot/pounds. Make a note to buy a 10x1100 V-Belt while you're at it. Save your old one as a spare.

BEFORE RE-INSTALLING YOUR PULLEY:
1. Install a New Water Pump. As stated previously, use a 1.9 Water Pump. Some of the Bolts are durn near impossible to get to with the Pulley installed. Do not re-install the Thermostat Housing just yet.
2. Lower Water Crossover Pipe (from pump to right side of engine). Remove, sandblast/clean and inspect. If severely rusted out, find another one, clean it and paint (I used BBQ Black High Heat, couple a coats). Replace the short hose (VW # N901287.03) because this thing is real hard to get to after the engine is installed, so a new one in my book is mandatory.
3. Now re-install your crank pulley and torque to proper specs.

DIPSTICK TUBE:
There's an O-Ring that goes into the case opening. Should be one in your gasket set. Install it before re-attaching the dipstick tube. This attaches to the Coolant Crossover Pipe from the Right Cylinder Head to the Thermostat Housing, but don't worry about that until you install the Thermostat Housing.

ENGINE TIN THAT GOES BELOW THE PUSHROD TUBES:
Remember, you removed these when removing the engine. Clean them up to a nice shine and take note of the attachment points where they meet the cylinder heads/exhaust. Most of the early ones have a hole where the bolt or stud from the head goes through. Remember how much of a b*tch it was to remove these? Well, take a pair of tin snips and using your new engine as a guide, snip the mount holes so that it opens the hole. The "O" now looks like a "U" so that it can just slip on or off the bolt/stud of the exhaust. Makes future repairs in this area a snap. While we're in this area, replace the Oil Pressure Switch on the Left Side of the case just under Cylinder's 3 & 4.

OIL PRESSURE SWITCH ABOVE OIL FILTER MOUNT:
This is for the "Dynamic" Oil Pressure Warning System used on 86-91 models. Thought about using it for an Oil Pressure Gauge Sender. Nope, Gauge Sender's too big and won't clear the Crank Pulley. So leave the original sender there as a plug. If there's no sender installed and there's a threaded hole, take any old oil pressure switch, teflon tape the threads, install it and forget about it.

OIL FILTER MOUNT:
It would be great to take advantage of the neat Oil Cooler installed on the 2.1 - BUT - to do so would entail replacing and reconfiguring your entire cooling pipe/hose system on the engine and engine compartment to the 86-91 style - BIG BUCKS. I tried every conceivable trick to be able use it with the 1.9, but so far, no go. So I removed the Cooler and the longer Filter Stud and used the 1.9 Filter Stud. OIL FILTER: Be sure to use an OE Oil Filter, they're the best (Mahle, Mann) VW # 070-115-561.

Save the Cooler and the Stud - I may come up with a way to retrofit something in the future.

EXHAUST SYSTEM:
My pipes were in pretty good shape with some rust. Sandblasted them and re-painted with Thermo-Tec's Hi-Heat Coating rated to an optimistic 2000F. Actually it's supposed to be used with their Exhaust Insulating Wrap, but several guys at the local FLAPS said it works very well on pipes as well. I've had minor flaking, but it held up pretty good for the first couple of years. I used the #12002 Aluminum color which when dry looks silvery. Looks nice. Use 2 coats and let it dry for 24 hours before installing. Used this on the muffler, tailpipe, collector pipes, brackets but not on the Catalytic - leave that natural (or replace if necessary). Or you can go the expensive route and have the exhaust pipes all ceramic-coated. Install exhaust pipes (with that engine tin and brackets I noted earlier) AFTER installing the Rear Carrier Mount Assembly and BEFORE installing Thermostat Housing. It's a lot easier to get to the fasteners. Don't install the Cat/Muffler until it's back in the vehicle. Engine's a lot easier to handle this way.

NOTE: Metal Side of Exhaust Flange Gaskets go towards the Engine Flange. Composition portion go towards the Pipe Flanges.

THERMOSTAT HOUSING:
After installing the exhaust system, install the Thermostat Housing to the Water Pump. Replace that little hose that connects between the Housing and the Left Cylinder Head (VW # N901287.03). Then mount the Coolant Crossover Pipe that goes to the Right Cylinder Head (Replace the White (or Yellow as sold by VW,) O-Ring that goes into the Housing, but don't use sealer on it - use sealer on just the Cylinder Head End Flange/Gasket). Install a New Thermostat (80C) and O-Ring. Dang Gasket Set did not have the O-Ring, so I had to pick one up at a local FLAPS (I bought two - one for a spare down the road). I did not use sealer (pretty tight fit here) on this O-Ring either, so make sure the mating flanges of the Thermostat Cover and Housing are nice and clean. I replaced the ECU Temp Sensor and the Gauge Sender primarily because they were unknown quantities to me. If you know your's work, keep 'em installed. Now attach the Oil Dipstick tube to the little bracket/flange on that Cross Over Pipe - Don't forget the O-Ring Seal.

FLUSHING AND PREPARING COOLING SYSTEM:
Before re-installing the engine I flushed the entire cooling and heater system in the vehicle with clear water to remove any old coolant. One major reason was that the previous owner(s) had used regular Prestone which was not Phosphate-Free. Also back flushed as well (flushed in reverse direction). Be sure to open the Heater Valve(s).

Wanted to run the cooler (76C) Fan Switch, but could not find a Deep 29mm Socket. So presently I am running the original switch which does work quite well.

RE-INSTALLING ENGINE INTO VEHICLE:
Now reassemble everything except the Fuel Injection stuff below and re-install engine back into the van using your removal procedure as a guide in reverse. The fuel Injection stuff's covered below after re-installation.

FUEL INJECTION SYSTEM:
I waited until after re-installing the engine to re-install the Fuel Injection Intake System for one primary reason: Re-connecting the Torque Converter Bolts would be a lot easier and left a lot more room to do it. But here's some necessary items to do before and while putting it back together on the engine:

FUEL INJECTORS: Mine had 82k miles and the van had been sitting for at least 1 1/2 years. So the gas turned pretty raunchy, so I had them rebuilt - good thing because the "Spray Cone" was horrible. If your's are fairly new/rebuilt and the van hasn't sat for a century, test them first as per Bentley, then reuse if OK. I have them done locally and it costs about $25 per injector. Much better than the high cost of new ones.

I installed the injectors AFTER reinstalling the the Center Air Plenum and Air Intake Runners. Used all new Fuel Hoses too throughout the engine compartment, re-using the insulating covers wherever possible. Used the "smooth" high pressure fuel hose VW # N20281.1 and all new clamps if the old ones didn't measure up.

CENTER AIR PLENUM:
Due to the design of the 2.1 case, the 1.9 plenum is not useable. However, the 1.9 Throttle Body must be installed because the 2.1 variety won't fit the 1.9 Air Intake Elbow coming from the Air Box.

When using a replacement (new) case for 1.9's or when upgrading to 2.1 using the Digijet, VW and Bentley says to use the 2.1 Center Air Plenum (025-133-055B). I have mentioned before that I had to use the 2.1 Air Intake Runners as well because short 1.9 connecting hoses are too small to fit the hose flanges on the Plenum. VW/Bentley makes no mention of this.

The other thing I failed to note was that a slight modification was needed to attach the 1.9 Throttle Body to the 2.1 Plenum. The Throttle Body mating flange on the 2.1 Plenum's "curl" is a little larger that it's 1.9 predecessor. Hmmmmm.......Looked at a 2.1 Throttle Body.....can't use that because the intake throat of that appears too large for the 1.9 Air Intake Elbow coming from the Air Box. Thanks to my best bud Cliff (who's done this before), he told me to initally install the 1.9 Throttle Body to the 2.1 Plenum WITHOUT the gasket and tighten it all the way. What happens is that the 1.9 TB's smaller taper will cause the Plenum's flange to "curl" even smaller to accept the Throttle Body's taper. After, that remove the Throttle Body then reinstall with the Seal. Fit perfectly. Does not harm, score or otherwise damage the Throttle Body or it's taper that I could see. Oh yes - use the original type 1.9 Throttle Body Seal (new of course). It's also the same seal used the the Air Cooled FI 75-83.

My only advice for tightening is to tighten it with the "tangs" of the Throttle Body just about flush with the Plenum screw flanges (Bentley does not offer a clue to the torque specs). You don't want it loose or semi tight though, otherwise vibration will cause it to come loose further and again you'll have the vacuum leak. Due to the shaping of the Throttle Body, the Seal, the Plenum and the tapered fit, the chances of "deforming" the seal is quite remote. The seal is ribbed to take advantage of the tapered fit of the part(s) and the "flanging edge" of the TB Seal should be the only part showing when tightened down. I don't recommend using a sealing agent such as Permatex as these pieces appear to have a very close fit and may not seat properly (mine would not when I tried) and I installed mine dry, so make sure all pieces are quite clean before assembly (See Piece of advice below).

One further note about tightening - be sure you have the securing screws aimed just right when initially installing the Throttle Body. If you cross-thread, you may have to find another Plenum. Of course, I had the Plenum and TB out of the vehicle while putting together the engine - it's a lot easier to do this way. If you're doing this job with the Plenum still installed onto the case in the vehicle, it's even more important to be careful when initially attaching these screws.

Another piece of advice - While you have the Throttle Body off, take some Carburetor Cleaner spray and clean the gunk/junk off of the Throttle Butterfly and the throat of the Throttle Body too. Mine was pretty gunked up after 82,000 miles due to the Oil Breathing function (which is proper of course). Do not remove any pieces off of the Throttle Body to do this, just spray clean it. Don't fiddle with the large "Idle Bypass Screw" either - do that when you've put everything back together and re-set everything according to the Bentley Bible. Be sure the mating surface of the Plenum is clean of gunk.

Now that's been done, install the Plenum onto the case. Don't install the Air Intake Runners just yet.

AIR INTAKE RUNNERS:
I am presently using the 1.9 FI System with one exception - because I am using a 2.1 case, I had to use a 2.1 Center Plenum (which came with the core motor) as specified in the VW fiche and in Bentley. What they don't say in Bentley or the fiche is that you also have to use the 2.1 Intake Runners to the Cylinder Heads as well, but again they came with the core motor. The reason is the boot/sleeves for the 1.9 Plenum to Intake Runners are just a hair too small for the 2.1 Plenum, so you have to use the 2.1 style - but then these are too large to use with the 1.9 Intake Runners to the Cylinder Heads to clamp down suffciently to prevent vacuum leaks.

Further Note: You'll notice another difference in the Left Intake Runner - The 1.9 variety has a stud protruding up from each runner pipe to attach the Heater Return Pipe (clean and paint this with BBQ Black Hi Heat). The 2.1 variety does not have this stud, but I found that didn't cause any problems. The right side Runner pipe stud (on both varieties) worked quite well in stabilizing the pipe and the hoses - not exactly rigid and there's a slight flex, but I don't think there's anything to worry about.

Now install the Air Intake Runners left and right. I didn't use sealer on the gaskets to the head because I didn't want to contaminate anything in the induction system at all. Be sure to tighten the Center Plenum Hose/Sleeve Connector Clamps too.

And that's about it. Make a note or diagram of the various vacuum lines just in case. It appeared pretty self-explanatory to me and Bentley has an excellent diagram as well.

Update:  The only large area replacement to be made since installation was the water pump at 65K miles - June, 2000.  I'll have a write-up on that soon. 

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