Let's see, to install a 6m into a MkII is a little different in what needs to be done for the different years. My swap was 6m into an '85. Things that need to be done...
1.) swap existing oil pan and oil pump over to the 6M (center drop 6m vs. front drop 5m)
2.) swap AC bracket (different)
3.) swap engine mounts (different)
4.) install flywheel (if yours is a 5spd, most 6m's have flexplates)
5.) install throttle cable bracket
6.) install the 5m distributor (6m unit had a different PN# on the side that my old one. 82 MKIIs definetly needs to use the old distributor)
7.) install old wiring harness (usually the harness is cut and would be different even if it wasn't)
8.) install BVSV (blue valve with 2 vacuum hose coming off it) on the T-stat housing. My 6m has a plug there. Probably would be easier to use the old housing, as I'd imagine that plug might be a bear to get out.
9.) intake manifold. Here is where it gets complicated. If you NEED an EGR valve for emissions (typically the visual/functional), you'll need to reuse your factory upper intake/EGR valve/EGR tube/EGR cooler on the back of the head. 6Ms (JDM cars in general) don't have EGR valves. Now if you have a 82-83 and some '84s, you'll also need to install the lower intake manifold to mate to the old upper intake. 6m intake manifolds have the D-shaped runners shared with the 85-86 and some 84 MkII. Earlier cars have the round runnered intakes. No matter what you should install the old throttle body. The 6m throttle body has a little different linkage and some of the vacuum ports are MIA.
10.) accesories. typically some or all of the accesories like the AC pump, alternator, and/or PS pump are typically missing.
note the injectors are the same
Now on to recommendations. Depending on what you have planned for your MkII, kind determine how you prep the engine. As sort of a disclaimer, many folks have had problems just thowing the engine in there as recieved. Typically in a year or 2 folks have had oil burning problems with 6m's. This is probably due to the fact these engine have been sitting around for many years. In increasing order of cost and difficultly these are what I'd recommend.
1. replace wear items. Typically things like the water pump, timing belt, spark plugs, plug wires, distrubtor cap and rotor, oil filter, new fluids, clutch, etc. This is generally required to meet the warranty on the engine anyhow.
2. buy a decent gasket kit and go through the motor and regasket it. The big ones to get changed are all the front and rear seals and also the valve stem seals. There'll never be an easier time to change these seals than when the motor is out of the car on a stand. Definetly stick with decent gasket sets, Toyota and Felpro would be my rec's. I always hear horror stories on some of those Made in <insert 3rd world country here> specials.
3. rebuild the motor, if you've got the cash and desire. Internally the 6m should be in really good shape and shouldn't need much machine work. The minimum on this one would be to dissassemble the motor, clean and inspect everything, do a light honing on the cylinders (remove the glaze), and install new rings and reinstall all the other parts. This would get you a engine that should run like new at the minimal cost. From here in addition you can do extra performance or relability mods. Things like balancing, valve grinds, new bearings, etc.
I'd definetly recommend doing 1 and 2. Do 3 if you have the money and you feel its worth it. In the end the 6m is a nice upgrade when you want something simple to do, looks like stock, and/or want to stick with a NA motor (or more ommph w/ a turbo conversion). As mentioned some folks have a problem above ~80mph with the check engine light coming on. The solution is either buying a 6m ECU, playing with the AFM, installing 210cc injectors, praying (if you're religous) or cross you fingers (if you're not). Or you can just ignore it or drive slower
. BTW no check engine light with mine with the 210CC injectors.
Aaron I