What are the differences 7A vs ABY blocks?

[karlblues2]

Hi guys
I have a mate who is turbo charging a 7A engined Audi 90Q. My question is basically, what the differences internally or in the block between the 2? Does the ABY/ 3B have extra cooling channels or stronger rods? Is it essentially the same as a 7A engine, but with a turbo strapped on and a 6 speed box attached? I know I'm over simplifying, but was concerned taht he thought he could get similar power out of his engine based on what I could get out of a stock ABY bottom end
All help and disparaging remarks welcome
Cheers
Karl
Oz

[JP]

pistons are different, and the exhaust valves are different, never bothered looking at the rods but as the pistons are the same as the 4pot KR engine I assume the rods are aswell which means they are not rifle drilled so less oiling to the wrist pin.

Stack the headgasket on a 7A and on stock rods, pistons and valves you can safely push your luck to 280hp. Anything more than that and one wants to start looking at swapping the internals for reliability, doesn't mean you can't push it further I just personally wouldn't on a reliable street car.

[porkkis]

7A is 82,5 bore
KR is 81 bore
They're most certainly not the same pistons.

[JP]

^^^^ my bad can't say I've ever had one apart to measure was going by the visual cut outs from pictures. VAG group being lazy as it is; 99.99% automatically becomes interchangeable as it's not economic to make multiple castings in mass production. Good to know they weren't on this occasion though as it will make a nice overbore for a KR then.

[Puglife]

Bore is different between the blocks.... crank is fine, but rods and pistons really need changing for any sizeable power upgrades.
Head doesnt have water manifold but this can, and has by many, be machined out.

[karlblues2]

Thanks guys
So you wouldn't be pushing 360bhp with a turbo on a 7A on stock internals?

[caterpillar]

only the conrods needs to bee changed, and may the bearings...;the high comp,may need to bee lowered, but not need.. if you use custom ecu ; dta, haltec, etc, you dont need either

[volcano rs]

exhaust valves are same too.

[JP]

exhaust valves are same too.

haven't seen a 7A head yet with sodium filled exhaust valves? So can't see how they are the same.

[Jamo]

exhaust valves are same too.

Thought the 7A had none sodium valves?

[volcano rs]

Thought the 7A had none sodium valves?

on my info sheet the same part numbers are used