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4G63 Crank Walk

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Hi,

Could you share your experience about what they call crank walk or when there is excessive wear of the Thrust Bearing in the 4G63 Evo 5-9? Maybe because of a bad clutch regulation issue?

Thanks.

Hi Cristian, I've had a LOT of experience with the 4G63 and their crank walk issues however this was an issue with the DSM and EVO 1-4 blocks. They changed the thrust arrangement in the EVO 5-9 4G63 and we never saw any failures in these engines. It'd be possible I imagine to still destroy the thrust bearing in the late model engines but it'd be the result of some basic issues like a clutch system that maintains pressure on the thrust bearing or low oil pressure.

In the early engines there were several issues that stacked up to cause the problem. The first is that the oil gallery that supplied the center main bearing doesn't align with the hole in the bearing shell. Secondly, because these engines used a full 360 deg thrust bearing it was easy to misalign the cradle and essentially reduce thrust clearance. This misalignment then also resulted in the crank only being supported by half the thrust bearing. Lastly we felt that there was insufficient oil flow to the thrust face.

We developed some modifications to the bearing itself and this fixed the issues, however you shouldn't need to do anything on the late model engines.

Hi Andre,

Thanks for the reply, I have a few questions..

1.- what would be the oil pressure needed by the EVO in idle and full boost to make it safe

2.- What axial play gap would be most advisable when a motor is just assembled? And how much do you believe measure increase after the break-in, Example if you built with 0.05mm after the break-in should grow to approx 0.08mm?

3.- what does the clutch system to damage thrust bearings?

4.- its normal to have the crank move back when clutch pedal is applied?

5.- Is it normal for the crankshaft to move back when you press the clutch pedal? when we use a dial indicator on the front of the crankshaft and press the clutch we can see that the crankshaft moves towards the gearbox the 0.16mm of play it has.

1/ can't comment

2/ that seems a little tight, but don't know about that engine

3/ the force applied by the release bearing to the pressure plate is directly applied to the crankshaft, the thrust bearing is what resists that force and keeps the crankshaft in the correct position. With stronger pressure plates and/or a poor supply of oil the oil film that is needed to prevent metal to metal contact can break down and cause rapid wear - it is the same principle as the big-end or main bearing operation, and failure. It is also why I REALLY dislike the clutch lockout in modern vehicles, as the oil film is most likely to fail on cold starts.

4/ yes, see above

5/ yes, see above - the later model Mitsi's use a pull clutch which would pull the rotating assemble towards the gearbox. The more conventional, push type will move it toward the engine.