Rebore one pot only?

[isham-research.freeserve.co.uk at pop.pol.net.uk]

> no one will sell you a single oversize piston. it affects the balance of
> the engine since one piston will be slightly heavier and not move w/ the
> same force as the rest. That bore will have more volume and affect the
> compression ratio. These are all minute problems, but an engine can destroy
> itself down the road. Your Audi engine was built and designed w/ fine
> tolerances which is why many of their engines last so long. No competent
> machine shop will bore only one cylinder. They all must be done, b/c the
> savings is negligible, esp. compared to engine rebuilding.

Both Mahle and Audi will sell single pistons.

The savings are NOT trivial.  Oversize pistons for the AAN engine list
at GBP135 - about $190 - _EACH_.  The saving if only one cylinder is
rebored is thus about $800.

Since the counterbalance weights on the crank are not touched during a
rebore, I assume oversize pistons weight the same as standard ones.
The compression ratio delta is negligible compared with the 2 bar
discrepancy allowed in the service documentation.

--
 Phil Payne
 UK Audi quattro Owners Club
 Phone +44 7785 302803   Fax: +44 7785 309674