80' D50 G52B rebuild questions

[KCGarage]

Hey guys, picked up an all original D50, it runs but has a "tick" in the top end. Pulled the head and had the valves and guides redone and the machine shop said the head/cam/valves were all in great shape. He said to check the balance or silent shaft as the bearing sometimes goes out and they can move around in the housing. Anybody have any experience with that? My next option is to drop the pan and check the rod bearings. Any help would be appreciated.

[pennyman1]

If it is a tick in the top end, it could be a warped or cracked exhaust manifold making the noise. Also check the cam bearing surfaces on the head - excessive wear can make the cam float and cause a tick. There are no cam bearings, so if the clearances are excessive, custom bearing would need to be made, or a different head would be needed to fix the issue.

[KCGarage]

So the exhaust manifold has a crack at the #3 junction. It's being welded up at the shop. The machine shop said the head/valves and cam are in great shape and appear to have been rebuilt recently. Man I hope it's just a cracked manifold causing the tick.

[KCGarage]

Upon removing the balancer shaft, I noticed some metal flakes around the oil holes on both oiling points. Looked into the front of the pan and pulled up some metal chunks. Now it's looking like a rod bearing. Going to pull the pan next
IMG_0271.jpg IMG_0272.jpg

[KCGarage]

Well here's the #1 rod (what's left of the bearing) IMG_0273.jpg

[pennyman1]

looks like full rebuild time unfortunately...

[KCGarage]

Yea, found a G52 short block fully rebuilt for sale. Probly just gonna buy that

[pennyman1]

makes sense - who knows what else was destroyed in that block. Check the cam bearing surfaces on the head to be sure there is no damage there.

[geezer101]

Pretty sure this is normal in regards to the oil gallery feed layout in Mitsubishi blocks (at least in the earlier designed engines) Vast majority of failures stem around #1 cylinder bottom end and more than likely the balance shaft bearings were badly worn causing an oil pressure drop. And +1 on pennymans' advice to check out the cam journals. When these engine suffer a major oil pressure failure, they eat themselves...

[KCGarage]

Thanks guys, the head is at the machine shop being assessed. Just waiting on valve guides for reassembly. The next question is does anybody want a cylinder or crank? The cylinder looks good but will need a hone. I'll post pictures after remove the motor and pull the cylinder and crank later today.