Rear Main Bearing Issue

[Castle Rock]

All.
Started to rebuild the engine today, or rather, was going to. Stopped because the mains I’d been given look wrong for the rear. The oilway doesn’t line up and the shell overhangs its seat.
Also, the three retaining bolts of the crank rear retainer don’t have a torque setting yet they look too important not to!

[philthehill]

The shells look alright to me. You have a oil passage to allow oil to the bearing. Just make sure that you have the right shell for the right housing.
Unless you have to do not remove the rear upper half of the oil thrower cover.
It is set at the factory and should not be removed. It is most important that the thrower cover is set correctly otherwise you will have oil leaking from the rear main/oil thrower.
The three bolts are usually secured by lock wire. The bolt heads should have holes drilled through them to allow fitment of the lock wire. If no wire holesd make sure that you have shake proof washers.
There is no specific torque quoted for the three bolts but they should be tightened to no more than 9lbf ft which is the generic torque for 1/4" UNF bolts.

[Castle Rock]

Thanks for reply.
Interesting, the 3 hex screws don’t have holes or lock wire so must have been apart at some point. I shall nip to the right torque and leave.

This picture prob shows better what I mean about the bearing shell. It looks like the whole thing is too offset - only 1/2 the oil way is free and the shell is too far one way.

[philthehill]

You must set the upper part of the oil thrower cover correctly - it is not just a case of fitting and tightening the three bolts - see the Minor workshop for details. You do not mention if there are any shake proof washers under the heads of the three bolts. There must be a form of locking for the three bolts.
As regards the bearing shells - how does the fit of the old shells compare to the new shells?
What size 'A' Series engine are you reconditioning?

[Castle Rock]

Hi.

The engine is a 1098, and the company that worked on the block removed the old shells and provided the new! So I don't have them and I doubt they do. I've ordered a set of shells from Moss and they look the same when offered up.

I think I'm going to have to modify the shells, but there must be a logical explanation!

The oil thrower piece has screws and spring washers - no wire and no holes for a wire lock.

[Bill_qaz]

If you Google search you can find a picture with bearing shell installed as a comparison. It may help to work out what's wrong. For example

Screenshot_20230331-111830_Google.jpg (135.35 KiB) Viewed 791 times

[philthehill]

I cannot see a reason that the shells that have been provided by your engine re-conditioner and MOSS are not the correct shells.
You have the 'tang' on the shell and the oil way in the shell is adequate. The positioning of the locating 'tang' (which determines where the shell is positioned) may have changed over the years to suit the shell becoming a generic shell for the 'A' Series.
The main thing to ensure is that the shell does not foul the oil thrower on the rear of the crankshaft. If it does not foul then the shells are suitable.
I would advise against modifying the shell.

[Castle Rock]

Thanks for advice. I think my main concern is that by simple logic the rear main is going to get 1/2 the oil it needs when compared to the other two mains!

[les]

I think the oil under pressure will ensure a good supply. If it’s the top picture you’re concerned about, It looks acceptable to me but I understand your initial concern.

[Castle Rock]

So we compromised with this! Slight grinding away with a tungsten dremel bit.
Happy now the oil can get there OK!

[les]

I see what you’ve done, however oil still has to travel through the so called ‘restricted’ area in question before it reaches your modification, so personally I don’t think your mod has made any difference. Yes I too would prefer the holes to be perfectly aligned but I still maintain the initial set up was adequate. If you’re happy with it, that’s all that matters.

[Bill_qaz]

In beginning of video same issue 10years ago and builder not concerned.
https://youtu.be/djoQQWUvlps