The lads at MetroManiacs send these 3 replies:
He's gunna have to pull the whole intake tree and ECU with it, prolly most everything under the hood. I also remember a possible really bad problem with engine mounts not being at all in the same spot, but that may have been an auto trans to a 5 speed trans mod that Charlo Barnes was doing. I would certainly NOT want to attempt this mod. I think the car should be kept 4 cyl and if he wants a 3 cyl he should buy one that way, but I may be wrong. If the engine mounts fit the 3 cyl out of the old car and he's willing to deal with any wire harness mods to the 4 cyl ECU, it may be OK. Changing a cluster is simple, but a whole dashboard I would not do. I could not even get one out of a car I was junking and did not care about!
-Carl
He will need to swap out the CV shafts as well, as the 4 cylinder to 3 cylinder ones are different. The tranny mount as well as the shifting rods should be way different too. The 4 cylinder engine moves the trans toward the drivers side, with the 3 cyl things move to the passenger side more. He should certainly find it to be a learning experience.
DJ
There are two separate factors at play here that lead me to suggest he
should leave it hell alone.
First, the newer cars are physically larger and 250 pounds heavier
than the older generation, the three cylinder is overstressed and
doesn't really deliver as it did in the 89-94. I owned two 3/5's and
two 4/5's in the newer body style, the three cylinders got 43mpg, and
the four cylinders got 40mpg. Both four cylinders had A/C too, so
they were carrying around an extra 45 lbs. That's not enough mileage
difference to make all that work worthwhile.
Secondly, the 98-01 four cylinder is the only truly modern engine
there ever was in a Metro, it's quite a gem. With 78K miles on it,
it's just getting broken in. I'd change the timing belt and water
pump, adjust the valves, and expect another 100K out of it before it
really needs any work.
Instrument panel will swap right in, but the tachometer will not work
without modification. The four cylinder has a direct ignition with
coil on plug and no distributor. There's a thread over at TeamSwift
about modifying the tach to work with the newer four.
Transmissions will swap easily, final drive gears are buried inside,
the last part that comes out of the case. If both trannies work, swap
the whole thing.
Don McC