(quoted from post at 11:05:52 10/26/22) I'm working on rebuilding a 640 tractor that had some engine damage
and while working with the machine shop we have an interesting problem.
The machine shop found the sleeves (both old and new) do not match the step in the deck.
The sleeves have a 180 thou step on the top, but the block has a 208 thou step. If the sleeve was pressed in, the sleeve would sit under the deck.
.....so [b:2aecc88b9a][i:2aecc88b9a]we're[/i:2aecc88b9a][/b:2aecc88b9a] wondering if this is correct ....
IMHO
You say, "[b:2aecc88b9a][i:2aecc88b9a]we're[/i:2aecc88b9a][/b:2aecc88b9a] wondering" as in both you and the machine shop.
If your machine shop is "wondering" if this is correct, run, don't walk away from that shop.
Having the sleeves' lip, be able to move 0.028 below the top of the deck is a recipe for disaster.
I'm not sure of the spec for your exact engine off the top of my head, but a typical spec is the sleeve needs to be .001 -- .002 or .003 [b:2aecc88b9a][i:2aecc88b9a]above[/b:2aecc88b9a][/i:2aecc88b9a] the deck. In reality it can be even (flush) with the top of the deck as long as it is not below.
Understand the reason for this.
As the pistons move up and down in the cylinder, a thousand or more times a minute, for hours upon hours, it will try to drag the sleeve with it, in either direction. This applies to all sleeves, wet, dry, pressed in, etc. The lip keeps the sleeve from moving downwards. The cylinder head, tightened against the top of the lip, keeps the sleeve from moving upwards. In your case, it seems there would be .028 room for movement. Even pressed in, with that amount of room, the sleeve can begin moving this distance. Maybe right away, maybe not until hours later. Eventually though, the lip can break enough that the sleeve can be dragged down to collide with the base of the connecting rod, or the crankshaft itself. Not pretty.
In some cases, depending on the design of the sleeves' lip, shims are used to bring the position of the lip back into spec.
Another solution is to bore the cylinder with a lip in the bore at the bottom. Then a custom sleeve can be pressed to this lip, and machined even with the deck. For me, this is the only scenario where I would allow a sleeve to not be standing slightly "proud" of the deck.
Oh yea, and get that repair manual!
This post was edited by jimtrs on 10/30/2022 at 09:12 am.