Replacing S54 crank hub

[sapote]

The dowel hole diameters are different. It's a press-fit on the sprocket and a clearance fit on the crank. I verified it by sliding the dowel into the crank before installing it onto the sprocket.

Then why it was difficult to install with new sleeve as you had said and needed to put sprocket in freezer?

[marksae]

Then why it was difficult to install with new sleeve as you had said and needed to put sprocket in freezer?

Well good news, I was finally able to install the new sprocket! Freezing the sprocket seemed to do the trick.

Sliding the sprocket into the main crank bearing bore was the difficult part. I believe the main bearing clearance range is from .0005" to .002", which means the sprocket would need to be almost perfectly perpendicular to the bore to slide in. Since I don't have a high precision alignment fixture for this job, my next best option was to use the crank pulley bolts as guides to keep the sprocket as aligned as possible. I lubed the sprocket OD and main bearing ID with the thinnest motor oil I had. The sprocket went in with gentle taps from a hammer. No excessive force required. So hopefully I didn't score the main bearing in the process.

[sapote]

Sliding the sprocket into the main crank bearing bore was the difficult part. I believe the main bearing clearance range is from .0005" to .002", which means the sprocket would need to be almost perfectly perpendicular to the bore to slide in.

No, the sprocket cannot be used as part of the crank bearing if you think it slides under the main bearing shells. The main bearing ID is larger than the sprocket OD at this area. Sprocket actually slides into the crank nose and this is the reason why freezing the sprocket helps in the installation, not the dowel sleeve.

[sapote]

Doesn't the sprocket fit into a bore in the crank? I would think you'd want to make it smaller by freezing to more easily fit into the bore in the crank?

You're right, that the crank nose has an under cut bore for the sprocket to slide in with some interference fit to ensure the sprocket is perfect concentric to the rotation.

[sapote]

On this subject, how to ensure that the sprocket and balancer were perfectly concentric in the crank nose when installed? A little off center will cause chain vibration and the balancer doing more harm than good.
On the pic below, could someone confirm how much radial plays between bolt 1 and the sprocket hole? Check at the bolt threaded section and also the bolt head OD. I believe the factory wanted to use this bolt in combination with the sleeve to ensure things are concentric, so the screw #1 must not have plays to the sprocket.

So the crank nose has an under cut bore for the sprocket to fit into the bore with interference to ensure the sprocket is perfect concentric, and the harmonic balancer with its center pilot boss slides into the sprocket center bore with interference to have concentricity.

[marksae]

Ok, thanks for the clarification. The sprocket really felt like an interference fit when I pulled the old one off and when installing the new one. I feel a lot better now knowing I didn't hammer it directly into a bearing surface.