Author Topic: Scoring on Camshaft lobes (Read 3539 times)

dhirsch · « **on:** December 13, 2006, 09:26:05 PM »

So, I just picked up an M42 with a blown timing chain to rebuild. I'm just starting to take it apart and there's some scoring on the camshaft journals. Does anyone know if this can just be cleaned up, or should I try to find a new set of cams and caps?

Thanks for your help,

David

Alpine003 · « **Reply #1 on:** December 14, 2006, 09:20:05 AM »

IMO, if you're not doing a full rebuild, don't sweat it and just reuse it.

If you're paranoid, I might have a set of cams in a week or so.

tim_s · « **Reply #2 on:** December 14, 2006, 02:03:11 PM »

Most M42 cams I've looked at need the bearings polished, same with the carriers. do it, it quietened mine right down.

dhirsch · « **Reply #3 on:** December 14, 2006, 04:34:16 PM »

Quote from: tim_s;15593

Most M42 cams I've looked at need the bearings polished, same with the carriers. do it, it quietened mine right down.

Thanks for the advise guys. I'll look into getting everything polished before the rebuild

sheepdog · « **Reply #4 on:** December 14, 2006, 07:42:44 PM »

Is the timing housing/oil pump trashed?

If so, that scoring may be due to a complete lack of oil. In that case, you may be looking at spun bearings and such.

dhirsch · « **Reply #5 on:** December 14, 2006, 07:46:14 PM »

Quote from: sheepdog;15614

Is the timing housing/oil pump trashed?

If so, that scoring may be due to a complete lack of oil. In that case, you may be looking at spun bearings and such.

Yikes. Hopefully it was just the failure of the timing chain. I guess I'll find out when I take the bottom end apart.

Alpine003 · « **Reply #6 on:** December 15, 2006, 08:22:43 AM »

Quote from: dhirsch;15615

Yikes. Hopefully it was just the failure of the timing chain. I guess I'll find out when I take the bottom end apart.

Hopefully you don't have bent valves.

dhirsch · « **Reply #7 on:** December 16, 2006, 06:52:04 AM »

Quote from: Alpine003;15635

Hopefully you don't have bent valves.

Definitly have bent valves, but I knew that before I bought the motor. Cylinders 1 and 3 made contact when the chain went. It looks like the 2 intake valves on cylinder 1 are definitly toast, and I'll probobly change the valves from cyl. 3 just to be safe.

I took everything apart yesterday and the crankshaft looks good.(all bearings were in their correct places and there wasn't any scoring on the crank)

Unfortunitly I broke the bolt that holds the vibration damper to the crank....off to a machine shop it goes.