Mech123

Calling all 2.8 30v experts.
I have a AHA out of a 1999 Audi A4 that I want yo use in a 2002 Passat.
The problem is that the crankshafts are different on the transmission end.
I would like to know if I can use the crankshaft out of the ATQ that is coming out of the Passat in the AHA.
I have both engines apart and they appear to have different connecting rods.
I was told by a knowledgeable mechanic that it will work since the crankshaft is balanced separately at the factory and the piston and rod sets are as well.
It seems to me though that the piston and rod weight should have a relationship to the balance of the crankshaft counterweights.
I have read here and on other forums that the AHA and ATQ engines are mechanically identical and that the only differences are the intake systems and a few sensors.
My investigation of both these engines side by side suggests that this is true externally but not internally as the rods are different.
I guess that if the rod piston combinations weight the same in each engine then the difference in the rod design should have no consequence on the balance and the cranks should be interchangeable.
Does anyone have any information or experience with this?

Prospeeder

Whats junk about the other engine? If your able to use the crank why not use the rods too and that sounds like it should work.

Mech123

The cranks have different ends on the transmission side.
Both cranks are in great condition.
I have measured both cranks journals and they are 54mm for the rods and 65mm for the mains. Neither have any wear marks or scratches at all.
I am trying to swap just the cranks as to avoid removing the pistons and the heads.
I have information from a member of another forum that the internals on all AHA and ATQ engines are balanced the same and that any part is interchangeable across either.
The different rod designs apparently weight the same which is what rely matters for my purposes.
Thanks for taking the time to reply.

Prospeeder

Oh I see, So again, why are you swapping engines? What was wrong with the original one. If the bottom end is good. Im gonna guess maybe broken timing belt bent valves? You could just swap the heads and call it a day.

Mech123

Yep. Broken timing belt and valves smashed into pistons.
Don't trust the 2 pistons that hit the valves really hard.
Also was told by a guy who works on these engines that the heads are always warped when you take them off.
I finished installing the crank last night and it is like new.
All journals were exactly in spec so i put in new bearings and plastigauged them. Buttoning up the engine today and installing it tomorrow.

Prospeeder

That guy has no idea what hes talking about. I have removed and revalved plenty of these heads and no warpage or need to machine them. Just remove the headbolts in reverse as the tightening sequence. i wouldnt be concerned about the pistons. I had one Passat 2.8 that a valve broke off and was sticking out of the middle of the piston with a big dent. Car runs fine, doesnt use oil and is one of my family members.