Help - Main Bearing problem
 

The center Main bearing went bad in a new 2.0 motor.
The problem is that only one of the bearing shells went to copper. The other shell is OK. Also the surface of the bad shell went bad only on one edge.

Case had been bored "20 over" & crank had been checked and polished. All new bearings.

I hope the attached picture shows enough detail.

Has anybody had this problem and found a solution??

Kenhttp://forums.pelicanparts.com/uploads/Kbearing.jpg

Fillet radius on the crank was ground incorrectly as in not large enough!

incorrectly torqued main bolts

Problem FOUND.

Plastigage shows bearing not flat. Bulged end is less than 0.001". Other side consitant 0.0015/.002.

Note grease was used on the good side to keep the Plastigage in place.

I do not know how common this is, but I will always use Plastgae from now on.

Kenhttp://forums.pelicanparts.com/uploads/Kh_main.jpg

how about a little lesson on when and where and how to use plastigage. i didn't use it on my first rebuild. had all machine work done, measured and assumed all was good. engine was 81 vanagon 2L.

Plastigage is a small plastic strip that can be obtained from most auto stores who supply local auto mechanics.

It comes in various sizes depending on the clearence to be measured.

It is placed on the bearing, or shaft. In the case on a 914 main bearing, the case is put together and torque to specifiction. If it were a rod, then the cap would be put on and torqued.

Becareful not to rotate the shaft as that would smear the plastigage.

You then take the case apart and measure the spread of the Plastigage.

A scale is printed on the package that shows the clearence depending on how wide the Plastigage is.

Ken
http://forums.pelicanparts.com/uploads/plasti.jpg

Ken, are you sure that's it? No problems with the main bearing saddle that Jake Raby is always talking about?

Milt,

I had the shop that did the line bore look at the case as well as check the crank. They is was OK.

The other half of the bearing was 0.002 across the FULL surface. This side was 0.0015 to < 0.001. I would think a saddle probelm would show up on both sides.

I will Plasigage it again with new bearings, sometime this week. I will add to this post what I find out.

Ken

Sounds like you have a "Collapsed" center main........I see this often.