Main bearing not so good

[dave in australia]

Last weekend, coming home from Melbourne on a club IMAD run, as I slowed down from 80 Km/h (50 Mph), to 50 Km/h (30 Mph), my engine started to make a loud thump noise. I nursed the car home, and thought it was a rod big end bearing. I was wrong, it was the rear main. I don't know if the goldish colour on the cap is a bronze repair, or babbitt discolouring caused by heat.

 

[rotorwrench]

I can't tell for sure by the photos but it may have been a layer of brass shim stock cut to fit in there. Folks used to put shoe leather and all sorts of stuff in the bearings to get them by for a little longer. Babbitt is generally thicker than whatever that is in there. It comes out in chunks when it breaks down.

 

[Kurt in NJ]

Looks like it lost oil
It could be that area was brazed in a attempt to have the Babbitt bonded to the cap

 

[Will N]

Do you guys have engine rebuilders who can pour and line bore babbit in Australia?

 

[rotorwrench]

If it was brazed, they didn't do anyone any favors. If it had a brass shim stock installed with a hole drilled or punched for the oil flow, slippage would block the flow.

It takes a lot of heat to braze a part. It would melt any babbitt that was ever there. The melting point on babbitt is lot lower than brass.

 

[Dan McEachern]

That is a '28 rear main cap and those are forged steel and not cast iron like the later caps.
The steel caps are quite tinnable and would not require a layer of braze in order to attempt tinning prior to pouring. I think you are just looking at the remans of a bearing that got really warm from a lack of lubrication. Most likely the oil supply got cut off and the bearing got hot enough for the babbit to melt and start wiping.

 

[nkaminar]

Dave, You are lucky you made it home. I am very happy for that but I am not happy about the condition of your engine.