Fused number 1 main bearing, causes?

[puremanb]

Did a search and couldn't find a lot of info.

New 1915cc engine, break in went perfectly, a few minutes into the first test drive the bearing fused and stopped the car dead in it's tracks. All clearances were in spec, spun freely at all points in the build, oil pressure was good.

Case was line bored .5mm.
All the bearing wear is concentric around the dowel pin side.

Is it possible that the line bore reduced the dowel pin clearance just enough to cause a small raised point on the bearing?

Should I file off a bit of the dowel for the next rebuild?

[jason]

Yes. They must be measured. It probably pushed the bearing over reducing the clearance to zero. Enough to turn freely, without space for oil it fused.

[puremanb]

[SBD]

You can measure the depth of the hole in the bearing and measure how far the pin sticks out of the block. Probably good to have a little clearance there.
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[Bajaman65]

It's easy to check the pin, just measure how high it is and compare it to how deep the hole in the bearing is. There are usually a few things that cause a bearing to freeze onto the crank, No Oil, not enough Oil, End Play to tight or the wrong size bearing. If it turns freely as assembly then you probably do not have a pin problem, but Never Rule It Out! Sorry that happened to your new engine. I am sure you will figure it out and let us know.

[modok]

if the clearance was in spec........ then what was it?

[raul arrese]

[modok]

It's usually caused by being too tight.
As the case heats up torque on the main bolts goes UP, and it clamps the crank.

Was it just too tight or oval or a high spot?? could be lots of things

[mark tucker]

I would guess wishful endplay.as in less than .003 in reality but pushed hard enough or deflection showing more than .003" add some heat and grab!! or something went through the oil gally&restricted the oil to that main. or some other stupid mistake/over sight.like hmm I dont recall but isant that rear bearing fed through the gally that almost gets pluged off when the rear main gally is taped&pluged......toofar inward.... a restriction there will show good oil pressure but the flow is reduced.even sealer can block it enough. if you have it all appart you can look at everything and find exzactly what did it.thats if you have the ability to do so.