Main Bearing Alignment

[set3422]

I just finished rebuilding my friend's block with stock parts due to budget constraint. What I noticed is that the main bearing (crank pulley side) on the lower half of bearing cap is mis-aligned toward the crank pulley. I did align the caps and bearings per astra gear website. What I did was first soft punch the caps toward the flywheel side, then pry the crank toward the pulley side. Stock main bolts were used so line hone was not necessary. Step torqued the main bolts from center to outer sides. Below is a quick sketch of how it looks like if done properly:


CRNK PLY.
I
I H Top Bearing
I H
I =============Flywheel
I H
I H Lower Bearing
I

Here's how a misaligned baring looks like:

PLY.
I
I ITop Bearing
I I
I =============Flywheel or
I H
I HLower Bearing
I


PLY.
I
I HTop Bearing
I H
I =============Flywheel
I I
I ILower Bearing
I

Now the real question. If the bearings are aligned on the thrust side, should it matter how the lower bearing looks like on the front side. All brearings are not manufactured with the same dimension. If were, we wouldn't have to align it in the first place. Here how it looks like:


CRNK PLY.
I
I__I Top Bearing
I__I
I =============Flywheel
I _H aligned on thrust side
I _H Lower Bearing
I


Thanks.

 

[set3422]

Perfectly aligned bearings


CRNK PLY.
I
I H Top Bearing
I H
I =============Flywheel
I H
I H Lower Bearing
I

 

[set3422]

Here's how a misaligned baring looks like:

PLY.
I
I ITop Bearing
I I
I =============Flywheel or
I H
I HLower Bearing
I

 

[set3422]

Here's how a misaligned baring looks like:

PLY.
I
I HTop Bearing
I H
I =============Flywheel
I I
I ILower Bearing
I

 

[set3422]

Now the real question. If the bearings are aligned on the thrust side, should it matter how the lower bearing looks like on the front side. All brearings are not manufactured with the same dimension. If were, we wouldn't have to align it in the first place. Here how it looks like:


CRNK PLY.
I
I__I Top Bearing
I__I
I =============Flywheel
I _H aligned on thrust side
I _H Lower Bearing
I


Thanks. [/B][/QUOTE]

 

[Defiant]

I read it really slowly, and several times, and looked at your pictures. I still don't know what you mean.

If the thrust bearing's in, how can you move the crank to "align" the others? Aren't they held in place by the anti-spin tab?

 

[NDgsx]

The front side of the bearing might not see much thrust loading, but I wouldn't want it swipping off my oil either. Pull the bearings and mic the thrust surface thickness on each of them. If it is thicker on the one bearing than lay down some six hundred grit sandpaper on a piece of glass and rub the front bearing side in a figure eight motion with light pressure to bring it in spec with the other bearing.
Or just buy another set of bearings if it's really different, that's what I would do. I've never run into a problem with mismatched bearings like that though.

 

[NDgsx]

Originally posted by Defiant
I read it really slowly, and several times, and looked at your pictures. I still don't know what you mean.

If the thrust bearing's in, how can you move the crank to "align" the others? Aren't they held in place by the anti-spin tab?

I thought he was just talking about the alignment of the thrust bearing surfaces, not the other main bearings.

 

[set3422]

Defiant & NDgsx,


Sorry for not being clear enough. Actually what I meant was the two halves main bearing closest to the front side (crank pulley). All the pictures were showing the main bearing. When all bearings (main & thrust) are aligned, the bearing sides facing the flywheel are all aligned because by applying thrust force on the flywheel with a pry bar.

I have corrected the last paragraph and it should be clearer now.

If the main bearings are aligned on the side facing the flywheel, should it matter how the lower main bearing looks like on the front side. All bearings are not manufactured with the same dimension. If they were, we wouldn't have to align it in the first place. Here how it looks like:


CRNK PLY.
I
I__I Top Bearing
I__I
I =============Flywheel <---------Thurst Force
I _H aligned on thrust side
I _H Lower Bearing
I


Thanks. [/B][/QUOTE] [/B][/QUOTE]