1. 6 bolt vs 7 bolt
It's commonly believed that the 4G63 7-bolt cranks found in the 2G Eclipse are more prone to developing crankwalk(abnormal thrust bearing wear that promotes side movement of the crank) than the predecessor 6-bolt blocks. What the 2G's have that the 1G's don't is an independent crank position sensor over the crank trigger plate. So with enough thrust bearing and/or crankshaft wear, the trigger plate starts to grind at the crank sensor fouling it and throwing a CEL. This was one of the points that made for a good argument since the 1G 6 bolt owners just didn't have a way of knowing without actually measuring the clearance.
The debate on whether or not the 7 bolt motors are more vulnerable will probably never end. All the theories in the world came up, some good some bad, and fixes promoted from various vendors trying to deceive the naive in trying to make a buck. Why go the route where so many have failed. It's better to listen to shops that actually build the 4G63 for a living than a dozen internet experts. For all I know, all but one shop who claim to have a crankwalk fix, recommends investing in a 6 bolt. I'm not even sure that one shop is still around anymore. So many have came and gone with a bad wrap in the DSM scene.
2. 6 bolt Parts Required - block only swap
| - | 6 bolt block and crank |
|---|---|
| - | 6 bolt flywheel (AWD or FWD, not interchangeable) |
| MD156465 | Oil pan |
| MD113024 | Oil pickup tube (strainer) |
| MD183240 | Oil pickup tube gasket |
| MS241071 | Oil pickup tube bolts x 2 (if you want new bolts) |
| MD141454 | Lower timing belt cover |
| MD972052 | Water pump assembly w/ gasket and o-ring |
| MD184529 | Cam/Crank angle sensor - '93-'94 black top hall effect sensor (MD121786, MD148855 - pre '93 optic sensor) |
| MD164533 | Hydraulic tensioner |
| MD130032 | Hydraulic tensioner arm |
| MD175762 | Front case (for use with helical gears)1 |
| MD149393 | Front case gasket |
| MD174581 | Oil pump drive gear (helical gear)1 |
| MD174582 | Oil pump driven gear (helical gear)1 |
| MD132912 | Oil filter housing - '89-'90 air cooled oil cooler ( MD157670- '91-'92 water cooled, MD122260 - no cooler). |
| MD149370 | Oil filter housing gasket (universal fit for all 3 types) |
*1 The early 6bolt front case use straight cut gears(which are discontinued). The later 6bolt case use helical gears which are the same parts used in the 1G/2G 7bolt.
2-1. Modification Required
If the block is from an automatic, the large bushing on the crank will need to be removed so the the flywheel sits flush with the crankshaft mating surface.
Oil filter housing selection will depend on the type of oil cooler you plan on using. Use the Water cooled type if you're pertaining the 2G's water/oil cooler.
2G drivers side motor mount will need to be cut to make space for the 1G water pump.
1G Lower timing belt cover needs to be cut for the 2G motor mount to fit through.
2G head stud holes will need to be enlarged for the larger 6bolt studs. One of the hole is used as the oil feed source to the head so it's important you don't skip this part just because the 6bolt studs fit.
Wiring the CAS. [attach picture]
On a 95-96 2G head : Swap plug wires 1 and 4 with 2 and 3.
Turbo water feed line will need to be T'd off the thermostat housing(hot side) as the 6bolt doesn't have a provision on the block as the 7bolt.
The timing belt hydraulic tensioner tool will no longer line up with the tensioner arm. You'll need to manually compress the tensioner whenever you do a timing job.
When using ARP main studs, the oil strainer (pickup tube) support leg will need to be cut off(or modified to fit). Use RED Loctite on the bolts!
3. Additional Parts Required for block and head swap
| - | 1G head |
|---|---|
| - | 1G intake manifold |
| - | 1G thermostat housing/water neck |
| MD147684 | 1G water pipe (MD163195 - for use with water cooled oil cooler) |
| MB605486 | 1G lower radiator hose |
3-1. Modification Required
Water pipe selection will depend on the type of oil cooler you use and also should consider the turbocharger's water return line plumbing if you're using a water cooled turbo. Pre -'90 and '91+, both have provision for the turbo water return line. Water pipes from '91+ which uses a water cooled oil cooler has another nipple near the water pump. Both nipple are missing on the NT water pipe. These are hard to get new, if you're looking for a NT pipe, Hyundai's water pipe can be an option. If you look around a lot of Hyundai parts are compatible and even OEM for Mitsubishi, such as the 6bolt timing belt hydraulic tensioner.
The counter weight on the transmission will need to be cut off as it interferes with the lower radiator hose.
Make a bracket to mount the 2G injector resistor pack to the 1G intake manifold.
Since the 1G intake doesn't have any provision for the 2G MDP sensor you'll need to T off the brake booster line. If it throws a CEL just block off the EGR and remove the MDP sensor since it isn't working properly anyway. It has no ill effect on drivability, but you'll probably lose MPG. Another option would be to get DSMlink and just disable the codes including the infamous Random Misfire. It makes things so much easier.
4. Random Misfire
The ECU is flagging a misfire condition because the crank sensor which originally drove the hyper accurate signal for the 2G ECU has now been replaced and simulated by the not so accurate 1G CAS. The only remedies for this symptom once you have it is:
- Wire in a potentiometer on the barometric sensor wire going to the ECU, thereby fooling the ECU into thinking you are at very high elevation (low barometric pressure) so it doesn't check for RM. This sounds simple, but if you don't tune the engine to compensate for the additional timing, you will end up turning your piston's to goo which also kills your turbo. (Not a recommended fix)
- Get your ECU socketed and buy a Keydiver chip. The best choice for the majority who wants plug and play.
- Buying DSMLink and clicking a tiny little checkbox which basically disables the ECU logic that checks for RM.
- Go with a standalone EMS.
The black top CAS did nothing to help RM in my case. It was a new unit from the factory with a harness built with new pins and shielded wires.