Been hovering for about a decade, finally posting a simple swap I am in the middle of and want to share a little info, as some of the waters are a little murky and information is a bit cloudy on what some of the issues are in swapping from d1 to d2 and vice versa. Situation: Mint 2002 D2 with a junk Bosch motor. Low mileage engine, but cylinder #7 casting surrounding the sleeve is actually a factory blemish problem, and has a 'dip' in it that will not allow a head gasket to mate securely. The blemish runs out to the coolant port, so even tophat liners wouldn't cure the gasket blowouts. Solution I am running with is simple- have a prefectly fine D1 block out of a 98- I am just giving the unit a refresh (rings, bearings, etc.) and swapping the externals.
Listing the changes and what information has been murky that keeps popping up in my searches. First off, a primary statement: This is a direct swap and is does not require any super special crud if you are technically above a salamander. Everything swaps from one block to the other just fine. Following is the noted changes:

1. Front cover. Use the bosch front cover. The oil pump pick up tube is connected to the front cover pump location. The old D1 oil pump suction tube mounted to the side of the block internally about 1/2 way to the rear of the engine internally- there is actually a cast journal/tube in the block that you can see that ran all the way to the front of the engine that lined up with the old D1 front cover- the oil pump used that journal and subsequent pick up tube to feed the pump. On the Bosch units, the journal port is blocked off on the front cover which renders it useless, and the pick up tube is mated (via 2 small bolts and an o-ring) to a pump housing and also is braced by a stud on crank journal no.4. Kind of stupid as the pick up screen is located in the same general position, but I assume that Bosch had to change stupid stuff to avoid patent issues. One small advantage is that the front cover no longer provides the seal between the oil pick up journal and the oil pump- under the Bosch system this is all internally relegated to within the pan. If you do this swap, you will have to remove the support stud (there is a steel spacer sleeve as well) and chuck that on your GEMS main cap. The GEMS main cap already has the machined thread port for the support, so nothing special there.

2. A lot of mention is made about having to TIG weld the Bosch CPS sensor bracket into place. As discussed by a hundred others, yes, they are different. And yes, they are TIG welded into position. But, you do not need a TIG welder to secure them into place. There is a perfectly sound and permanent way to secure them without welding. And for those who may disagree, that is fine- I have a TIG welder and do it all the time. But I found a super easy workaround that does not include JB weld or any such foolery. Oddly enough, and for what reason I know not, along the bosses for the oil pan to mate to at the rear of the engine (looking at the motor, oil pan off, upside down, crank exposed, etc.) there are two bolts on the D1 GEMS block screwed into the flat surface (parallel with the oil pan bolts). One on each side of the rear main caps, but outside the oil pan (if looking at the original D1 pan). They take a 12 or 10 mm socket to remove, and for whatever reason they have the brass crush washers used in banjo bolt (brake caliper) applications on them. I pulled them both, and blew compressed air into their threads, and walla- on the CPS sensor side- nothing. No release or bypass of air. On the starter side, there is a small orifice that allows air to escape out of the webbing on the rear of the block where the threads acutally cut into a thin area of cast material- nothing crucial and not an issue. The interesting thing is that on the side of the engine where the CPS sensor is located, the threaeded area where the bolt had been (where I removed it) happens to be perfectly centered right above and fairly centric to the Bosch CPS housing that everyone seems to insist on TIG welding in. On both the GEMS and the Bosch CPS units, there is a dowel pin that sets the correct alignment for the sensor housing. A few moments with a die grinder and you have the Bosch one out, the GEMS one out, and the Bosch one ready to go into the GEMS block. File or grind away any excess TIG welded bumps or material to get the CPS sensor housing (brachet, whatever) to mate nice and flat to the donor GEMS block (you can't screw it up, it only fits in one way), get it flush, then take a small drill and drill down the exposed threads (from the removed mystery bolt), drill a small recess (divot) into the sensor housing, go grab a metric allen key bearing lock screw (like as in a pillow block application) so that there is no bolt head above the block surface-oil pan mating area), throw some loctite on it and you now have a grub screw locking the housing into position that cannot go anywhere and does not allow your CPS sensor housing to wiggle- at all. Plus, no need for TIG welding or praying for JB weld epoxy.
3. Cam Bearing installation and whatnot: Not that everyone would be doing this, but I've been messing with these suckers since I was 12. Install and removal tools are cheap. Amazon has them for around 60 bucks. If you want to save a little time and avoid dealing with a machine shop and want a fairly tight fit, using the old cam as a cuting tool works really well if you know how to sharpen a drill bit. Slap a set of unfinished bearings in (align the oiling holes correctly) and cut your own profile on an old cam (the amount of wear on a cam is super super minimal, as long as it has been properly oiled- cam bearings are designed to take whatever wear will happen) set the motor vertical and grunt a little. Use an old timing chain gear on the camshaft, build yourself a bracket to turn it with some decent leverage, throw some cutting oil on the mother, and go to town. About the time you break a sweat you will have line bored a beautiful profile into your new cam bearings, and your new cam will slide right in with tighter tolerances than if you used finished bearings. This step is for those that have a little more familiarity with such crud, but is not difficult to accomplish.
4. Knock sensors. There was a lot of info about knock sensors being mounted differently and such. Plenty of worry about having to rewire and whatnot. It is all crap. The old D1 sensors screwed in with a bolt. Something like an m14 or so. The new Bosch sensors have a special stud that starts with a m14 or whatever and necks down to an m10 or so. Just remove the old stud (mine came out with the nuts as I removed them they were so loose) and plant the new studs into the same positions.
5. Cam position sensor. They look the same but they are different. One is longer than the other, but I think the pickup is the same and would probably work (don't try it though) as the plug looks the same as well. Looks like a simple 3 wire sensor either way. The part numbers are different though, and the D1 unit has the longer pigtail on it (just in case).

Anyway, that is the only crud I felt was even worth mentioning. The rest is basically the same. The oil pans are different, but the bolt patterns match and whatnot. If you ever got hesitant about taking an older GEMS block and using it for a Bosch application, do it. The quality control is far better, and is visually noticeable. One other note- lengthen the coil pack signal wires and mount the coil packs for the Bosch system somewhere else and make your own spark plug wires. The extra time you spend doing that saves your sanity when installing new wires on a fresh Bosch install.

 

hello mate im doing a swap like this today i have a d1 4.0 the donor and a 4.0 d2 with a compression leak bettween the headcylinder and block thanks for your information greetings from panama