Replacing S54 crank hub

[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.

[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.

[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]

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.

[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]

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]

Assuming the hole on the crank and on the sprocket are the same, then there is 50% chance the dowel sleeve will stay with the crank or with the sprocket when removing the sprocket.

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.

[sapote]

The dowel between the sprocket and crank is pressed onto the sprocket.

Assuming the hole on the crank and on the sprocket are the same, then there is 50% chance the dowel sleeve will stay with the crank or with the sprocket when removing the sprocket.

[marksae]

Not the sprocket itself but the dowel sleeve fitted on the crank. So the sleeve to be in freezer if needed, then the sleeve should slide into the crank and sprocket easily.

The dowel between the sprocket and crank is pressed onto the sprocket.

[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?

Not the sprocket itself but the dowel sleeve fitted on the crank. So the sleeve to be in freezer if needed, then the sleeve should slide into the crank and sprocket easily.

[eacmen]

What in the freezer -- the crank? I don't think you want to put the new sprocket (not hub as title says) in freezer, it should be baked to 300F.

I'm curious of how did you know about the broken dowel pin with the 4 Torx bolts locking the sprocket in place solid? Are these bolts loose? Also there are 2 dowels: a large sleeve and a smaller pin and so which one broken?

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?

[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.

[sapote]

"I’ll admit I never had to do this job, but a day in the freezer might make the part fit easier."

great suggestion! I will do that.

I would freeze the dowel sleeve and bake the sprocket to 300F, then install sleeve on the crank first, then sprocket over.
I'm curious of how did you know about the broken dowel pin with the 4 Torx bolts locking the sprocket in place solid? Are these bolts loose? Also there are 2 dowels: a large sleeve and a smaller pin and so which one broken?

[marksae]

I’ll admit I never had to do this job, but a day in the freezer might make the part fit easier.

great suggestion! I will do that.

[eacmen]

Okay, I was able to get it out. Like you suggested, I hammered it from a few different angles and saw that it moved a little, so I ended up just prying it a little at a time from the left and right sides until it came out. Now I'm having a really hard time getting the new one back in. I don't want to hammer it in and score the main bearing.

I’ll admit I never had to do this job, but a day in the freezer might make the part fit easier.