Last month my 1982 280GE W460 RHD LWB g wagon engine broke something inside. I turned to TradeMe, New Zealand's rather unique national auction site where ordinary people list stuff for sale as auctions - sort of like a combination of eBay and Craigslist (but without the scammers).

I found a 1982 (?) LHD supposedly Japanese Domestic Import 280E sedan with documented 64,000 km (40,000 miles) and a M110-984 engine. Rather than try to fix my M110-994 (estimates $4,000 to $8,000 and out of service for months as the experts are booked), I did a swap at the workshop that was selling the sedan on behalf of a customer ($1,000 - all of which I got back by selling the engine-less sedan and transmission). The workshop let me bring my tools and do all the swap-over work while they did the heavy lifting of pulling and reinstalling the power train.

Yesterday, they tried to crank the motor over to see if anything leaked, but were pleasantly surprised when it instantly fired up (with the exhaust disconnected... very loud).

Here is what I found replacing a RHD 994 G wagon long block with a LHD 984 sedan long block:

• The 984 came with pollution controls and a cat; the 994 had none (and uses a different designed exhaust manifold), that meant removing the pump, a lot of pipes, and a whole lot of vacuum bits. Engine bay looks a lot less complicated.
• Removed the AC compressor and tossed it in the boot of the sedan. This is New Zealand where we don't do heat and it's one less thing to break. Engine bay is a lot more accessible without it.
• The mounting placement for the alternator bracket is different, but works in the G wagon. However, as the 984 alternator case was broken, I found I had to punch out sleeves in it because the bolts used by the 984 are smaller in diameter. Because they are smaller, it also uses a second plastic sleeve inside the 984's metal sleeve which means it must have a grounding strap to the alternator.
• At the exhaust portal to which the manifolds bolt up, there are six air injectors. I was not up for tearing the engine apart to swap over, so I took a very large round steel plug and plugged the rubber air hose.
• The mounting point for the power steering is different, but the hoses fit, so I used the sedan mounts and it works fine.
• I completely swapped over the K-jectronic system because mine was refurbished with an aftermarket digital WUR and the sedan system was in poor shape. This meant all the linkage came over, so I don't know if the sedan linkage was different but I presume it is - especially as the sedan was LHD and the G wagon is RHD. Ditto air filter housing.
• Changed the motor mounts - very different
• Changed the exhaust manifolds - very different. Note to Newbies: Most of the bolts unscrewed from the block rather than the nut coming off. Then when reinstalling, the nut starts to move, resulting in the stud sticking out, which means it has fewer threads holding it in. To overcome this, use a second nut jammed on the first so it turns the stud, not the nut. When it is seated, back off the "jammer" nut and torque to spec. Also, while I got lucky and all the studs or nuts came off, be very careful to not shear a stud requiring drilling out. The last stud I reinstalled snapped with very little torque, so the manifold had to come off again. Luckily it snapped so I could remove it with vice grips. If in doubt, use penetrating liquid three days before removal. Google it.
• Changed the oil filter housing because the gwagon has oil cooler pipes
• Used the 984 starter solinoid but used the 994 starter because the 994 had an intermittant problem. Slightly different wiring.
• After removing the smaller part of the 984 oil sump (a two part design in contrast with the 994 which is one big pan) and finding the pump is the same in both, I made the decision to stick with the smaller 984 sump. This was a pragmatic decision because we did not have a replacement gasket, the g-wagon is used as a farm vehicle that is driven about 600 miles a year, and removing and replacing just means one more set of bolts that can shear off. And in NZ oil is obscenely expensive. I presume the 994 sump is to have more oil when heavy duty work heats it up, and the shape means no oil starvation when driving 45° slopes; neither of which is relevant to our use. But I will keep the 994 sump so when the G wagon is passed on to its next custodian, and added a label in the engine compartment so they know the sump on the engine is the 984 size (also notes the Odometer reading at the time the 64,000 K motor went in).
• I had hoped the 984's 722.1 transmission would be a bolt in, because it is such a low-km tranny, but it is not. Different shifting mechanism, different length, diffferent electronics, etc. In the too-hard basket for 600 miles a year... and I then put it up for sale and got all my money back on the sedan, so the engine was basically free.

I have not yet driven the g-wagon, as it will be next week before it's all done. The one thing that is very unclear is if I will end up with a 180hp or 140 hp engine. Have a look at this 280 manual where page 00-015-/3 suggests it is 140 hp 8:1 compression, while chart 00-001 two pages later says 110.984 output is 130 kW (174 hp) and elsewhere I was told it is 9:1 compression. Here's hoping.