Walked 7bolt 2.4 Results

[Raptor]

Okay, finally Chris's walked 7 bolt 2.4 is torn down and the reasons for it's problems can be assessed. All the bearings in this engine look like new with the obvious exception of the thrust bearing. The block is perfect and suffered no damage as the bearing still had adequate material on both sides to protect it. The remaining thrust surface on both upper and lower shells are exactly the same thickness which means that they were not out of alignment in any way. There is no difference in dimension from side to side thickness meaning they were not cocked to one direction or the other and when assembled without the bearings, the thrust surfaces on the block and the cap line up perfectly with very little movement possible due to the CRCO bushings. Now what caused it to wear? Well, as said before, the rest of the bearings are in perfect shape so there could not have been oiling issues at least in the main galley. The only thing somewhat obvious is the wear on the crank itself and the bearing. The bearing should have worn much furthur than the crank but it doesn't look to be the case. The crank has a fair amount of wear for the amount of damage to the bearing. That does support the case that the 7 bolts have looser/weeker grain structure in both the block and the crank and are most likely more effected by the heavy clutch pressures than the 6 bolt blocks/cranks. I would hope the cranks are nitrided equally on the thrust surfaces, but maybe they are not.

We are going to try using H rated bearings and having the crank repaired if possible. The clutch is being replaced with a twin disc and I am hoping that that solves any furthur issues with crankwalk on this engine at least.

Any useful input is welcome. Any stupid input will be dealt with accordingly.