Hi all,
I just thought it might be worth sharing some advice I was given from a trusted engine specialist regarding my A10's sleeved barrel.
Basically the guy reckoned I should not allow the sleeve to be bored such that the resultant wall thickness is less than 1 mm, as going thinner than 1 mm is not worth the risk of the sleeve cracking and/or the sleeve moving in the barrel. Basically it's one of those "it might be ok but...." type decisions.
In my case the sleeves are (as near as I can tell) 1.5 mm thick wall and it's on std (nominal) bore of 70.00mm. So the barrel must have been bored to around 73mm to accept them, which is the equivalent of +120 thou oversize.
If I took the advice of the specialist I could theoretically bore the sleeves (twice) to 71 mm and keep to the 1 mm wall thickness recommendation, 71mm is +040.
Hopefully I will never have to decide whether to bore the sleeves to +040, or even +020! Along the same lines I hope to never find out how feasible it is to reline a barrel that has been relined before.....
I've not had any advice on "when" to re-sleeve instead of bore to the next size but I guess it's another "it might be ok but...." decisions based around whether the A10 barrel will become more prone to failing with (say) +100" pistons fitted, than if a liner was fitted - the theory being a liner will add to the strength of the barrel, particularly the stubs, and +100 bore will make the stubs quite a bit weaker than standard.
Here's some figures, remembering these sizes are "nominal" and bores are usually made to suit the brand (and exact size) of a given piston.
Bore/dia Nominal Size
70.00 Std bore size for an A10
70.50 +020"
71.00 +040"
71.50 +060"
72.00 +080"
72.50 +100"
73.00 +120"