Cylinder bore wear tolerance

[Rusty]

Had my spare block checked and the bore on cylinder 5 has 2 thou wear. What is the tolerance on cylinder bore diameter and if it's out, can I run 82mm pistons on the stock head gasket?

[Error404]

82mm pistons are fine on the stock MLS gasket

0.05mm wear from memory I think is within range but certainly towards bottom size. Trouble is the wear will probably be oval so the bores will always be compromised even if the wear is within factory spec. You need to measure the piston skirts too

[Rusty]

It's with Aelred, so I'm sure he'll do what needs to be done.

It's only 1 cylinder, so I could get it sleeved but there's a bit of me that wants to go 82 or even 82.5mm bore

Wait and see.

[Thuppu]

Factory spec piston to wall clearence is 0.03mm, piston size 80.98mm and cylinder bore 81.01mm. Wear limit for the piston is 0.04mm and for the cylinder 0.08mm, so maximum piston to wall clearence allowed is 0.15mm(whitch is quite huge). Piston ring factory spec gap is 0.15-0.35mm. Wear limit 1mm.

[Error404]

I had the same issue and I fitted new 82mm Wossners

[Rusty]

0.15mm is not an insignificant amount

I'll take advice on what route to go, as I could always just sleeve the affected cylinder, could I not?

[Error404]

Cyl 5 might be the most worn but the others won't be far behind, to do a proper job I am sure they will all need doing.
Cost of standard sleeving is not far adrift of a set of new pistons when I looked into it ~ £100 a pot. You can go crazy if you want with ductile liners!

[Rusty]

82 or 82.5??? Will wait and see what comes back. I do 2k a year, so it's not like it'll wear out in the next week

[Thuppu]

82 is easier with the headgasket.

[diesel des]

I did my stroker 82.5 with a special machined mls gasket from hank in the states. Used wossner pistons. Seems ok 500 miles in with no knock from cold as the wossners run tight tolerances compared to other aftermarket pistons.

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[Rusty]

82 it is then.

[UrS4boy]

Had my spare block checked and the bore on cylinder 5 has 2 thou wear. What is the tolerance on cylinder bore diameter and if it's out, can I run 82mm pistons on the stock head gasket?

Pgs 36/93 and 37/93

http://s2-audi.co.uk/workshop/aan/aan.pdf

[gnutz2]

I used wossner 82.5 pistons and getting a gasket to to fit was a nightmare, the standard MLS gasket is 82mm and cannot be bored out because of the fire ring. I ended up modifying the pistons so they didn't come above the deck (which wasn't ideal), this allows me to use the standard gasket.

Why not 81.5? Or 81.25?

[diesel des]

The stock mls gasket can be machined out as far a 83 mm by hank at iroz in the us....

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[gnutz2]

I've tried machining them out in the past and every time the fire ring has come loose and fallen out. I put them on the car anyway and they didn't seal and pressurized the cooling system.