83mm oversized pistons on AAN pros and cons

[Morris400]

So ive been pondering with wither or not i should keep my 83mm pistons or stick with stock pistons on my coupe build. So im looking to you all for a detailed list of pros and cons on running 83mm pistons on an AAN with stock crank. Now i already have the pistons, and all the parts for the build. Just need to take it all in to the machine shop for the block to be done.

Bit of a back story, i bought a 90 coupe quattro project car and it included all the parts i need for the 83mm build minus machine work. So cost albeit is a factor for most when considering this type of build, for me its not a huge concern as i have all the $$$ parts.

my main condern is with 83mm, does it thin the walls to much?, does it limit how much power i can push on the block? Does it reduce reliability on higher boost applications?

Pros
- more displacement (2.3l)
- more power ?
- more TQ ?
- cool to say bored to 83mm

Cons (pertty much all $$$)
- cost of pistons
- machinest costs (can be over 1k)
- custom headgasket availability
- custom tuning ( every car needs it i suspose)
- reliability (is this a factor)
- cyl wall to thin? ( is 83mm to much ?)

Id like to hear what everyone thinks.

Kenny

[_ShurikeN]

Cylinder wall is definitely enough if it is 82.5 block originally.
Do piston already have rings with them? Is there a way to source extra ring set in emergency case?
Is there a source for custom gasket?
CR should be re-calculated (if it bothers).


Such config is possible.

Living in a country where cylinder block number appears in car registration documents I seriously keep in mind 83mm build to stay a bit safer with law.
For the situ when the cylinder block is a replacement part 83mm build is not that worthy.

[Morris400]

Cylinder wall is definitely enough if it is 82.5 block originally.
Do piston already have rings with them? Is there a way to source extra ring set in emergency case?
Is there a source for custom gasket?
CR should be re-calculated (if it bothers).


Such config is possible.

Living in a country where cylinder block number appears in car registration documents I seriously keep in mind 83mm build to stay a bit safer with law.
For the situ when the cylinder block is a replacement part 83mm build is not that worthy.

The pistons do have file to fit rings with them. I could get a spare set if needed. The block is an AAN block, so not 82.5 originally.

I do have a head gasket, its been machined out to 83mm.

As for the Law here, our engine block numbers dont apear on registration so thats not a concern.

[steve briance]

I bored out an 81mm bore 3B block to 82.5mm for use building up a fresh 7A. The basic casting is the same across the board as far as I know, there are minor differences between the blocks as; 3b had turbo oil return line, 7a doesn't. The important thing is that in 7a form, the casting is there for the oil feed, just not machined. Audi wouldn't invest in a casting per piston size, I think 83mm will be no problem... It is only 0.25mm each side of the cylinder after all.

[Quattroking]

Athena gaskets are available, i'm doing a very similar bore build and brought this gasket. (not used yet so don't know quality)

the website is crap: http://www.athenaparts.com/auto-raci...sket_line.html

where i got mine from: https://fcp-engineering.com/en/audi-...00mm-bore.html