[y72ss]

After only 200 mile the main bearing are down to the brass.I think my machine shop made a mistake, they polish the crank and said I needed under size bearing. The crank was not tight in the block when I put it in, but the oil pressure was very high(70-80 psi) when I started the motor up.200 miles later and the oil light came on and the motor had a knock.The under size bearing were installed on the mains and rods. The rod bearings look fine.Anyone have a theory as to what happen?

 

[buenymayor]

How much clearance did the bearings have when you put the engine together?

 

[y72ss]

How much clearance did the bearings have when you put the engine together?

I don't remember ,it been 6 months ago. I checked it with plastigage and I'm not sure how accurate that stuff is.

 

[BillsCamino]

George,
I don't have a bore guage here but I do have a set of mics so you could mic the crank journals. Should I bring them to the meeting today?
Don't trust plastigage...

 

[y72ss]

Thanks Bill, but I'm going to take the crank and bearing back to the machine shop tomorrow.

 

[Wolfplace]

After only 200 mile the main bearing are down to the brass.I think my machine shop made a mistake, they polish the crank and said I needed under size bearing. The crank was not tight in the block when I put it in, but the oil pressure was very high(70-80 psi) when I started the motor up.200 miles later and the oil light came on and the motor had a knock.The under size bearing were installed on the mains and rods. The rod bearings look fine.Anyone have a theory as to what happen?

=
If they are down to copper I can almost guarantee it had nothing to do with clearance.
In the majority of cases this is dirt plain & simple
A picture would be nice
Now if they were burnt this is a different story.

What was used to clean the block?
Heads?
Did you check all oil passages?
Clean the crank passages?
Did you get any where near the engine with one of those cute little abrasive discs like the 3m ones?

I have redone a few engines for repair shops that have just changed intake gaskets & used these things & of course "didn't get anything into the engine as they had rags in the lifter valley"
Took out every bearing in the engine within a couple of hundred miles,,

 

[Schurkey]

=
Did you get any where near the engine with one of those cute little abrasive discs like the 3m ones?

I have redone a few engines for repair shops that have just changed intake gaskets & used these things & of course "didn't get anything into the engine as they had rags in the lifter valley"
Took out every bearing in the engine within a couple of hundred miles,,

Yeah, silicon carbide (sand) in the oil makes for unhappy bearings, all right. Those abrasive discs do a great job of removing aluminum from aluminum castings, too. It's a real treat to put a straight edge on the gasket surfaces of aluminum parts that have been "cleaned" with them.

 

[CNC BLOCKS N/E]

We have had some blocks come in the shop with the same problems and 99% of the time the block was not striped properly before cleaning as on many 010 blocks they have a pressed in plug at the top of the block that has to be removed and the hole had to be machined for the proper pipe plug. And leveing those plugs in during the cleaning traps all the sluge and debis in the oil galley and up on start up it pushes all the debis in tho the bearings causing premature bearing wear.

Now hopfully we are talking a SBC if not the all the plugs must be removed to properly clean the block.

Here is a pic of where the plug is and showing taping the hole out for a 1/4 pipe plug.