Audi A6 engine, piston shot through the valve, can this be fixed?

Remove the spark plugs and measuring the distance through the plug holes with a rod, very gently turn the crankshaft (either way) until you are certain all the pistons are well below tdc and then gently bring the camshaft(s) to the timing position, followed by bringing the crank to the timing position.

Any specularion on amount of damage is pointless, you need ro take the head off and inspect pisons and valves. The valves may appear ok but if contact has been made with a piston, you will know this by obseving pitting on the top of the piston where the valve has hit, will probably mean bent valves.
There is a second point, I do not know if this is a safe or an interference engine.
If it is a safe engine the valves will not overlap with the pistons at any point, they will not occupy the same space at any point in the combustion cycle so there will be no damage in this eventuality.
Safe engines are, however, few.
I might obtain a used head from a breaker is there is too much valve damage.

the Audi 2.7L V6 30 valve engine has a Variable Valve Timing that is chain driven.

ally head 75lbs ,timing marks i honestly cannot remember ,do it old fashioned way time it to no1 with valves closed on no1 then you can see where or what the pmarks should be ,do not use starter motor ,always crank engine by hand 360? to ensure valves clear

motor is more than likly shot far as bending valves and what not not a cheap fix

If this is an interference type engine then yeas there is a real chance you could have major internal damage, such as a piston hitting a valve. If it is not an interference engine then there should be know issue other then a new belt, tensioner and water pump.
I hope this may have helped you,
Tom

It could be as simple as replacing an idle air valve, or could be something electronic. Really needs to be hooked up to a machine to be properly diagnosed.

HI,AT WHAT SPEED DID THIS HAPPEN,IF AT IDLE OR VERY LOW SPEED,HAVE A NEW BELT FITTED IF IT RUNS NORMALLY YOU ARE LUCKY,IF IT RUN ROUGH WITH BAD MISFIRE OR NOT STARTING AT ALL THE VALVES ARE BENT,PLEASE LET ME KNOW,ANDY.

change o2 sensors every 60,000 miles and use iridium plugs they will outlast engine.
check engine light will not come on until sensors are completely shot,this also goes for your mass air flow,had same issues with 99 beetle happened at 80,000 miles,changed all three items ended up with 35mpg after getting 24mpg before fix.parts are cheap on ebay.

Hi,
This is probably one of the worst things that can happen.
If it only jumped by a few teeth, then two of the pistons would have come up and found valves in the way. At this point, a couple of things normally happen. -
1 the engine siezes solid as there is nowhere for the valves to go.
2 The valves get bent, and the piston heads damaged.
3 The camshaft is stressed, and rockers can shear off as the valves are pushed back.

It usually results in damage to - Cylinder head, 2 cylinders (at least) - All damaged valves need replacing. Camshaft and rockers need crack-detecting, and/or replacing.

Most of the damage is restricted to the head, which needs taking off. It may be more cost effective at this point to replace the entire head from another scrapped vehicle than replacing parts individually - as you may miss small cracks, but this is a judgement call for cost vs time.

Hope this answers your question completely.