Rebore one pot only?

[Freed, David (Exchange)]

Wow, I can actually answer a question from the knowledge master.  Phil, I
ran an automotive machine shop so I can talk from experience.  The first
question is how badly scored?  As you overbore, the cc's of that specific
cylinder increases and so does the horsepower of that cylinder.  Add the age
of the motor and we are factoring in the fading power of the other
cylinders.  This creates an imbalance of power between cylinders and the
engine runs rough.  If the motor is low mileage and requires only a .020"
overbore then you won't notice much problems.  If you're boring .060" on an
old motor, than it will be more noticeable.  Obviously cost is a factor here
because your time to disassemble the motor to this point is more than the
cost of the extra pistons and machining.  It's a judgment call based on what
the owner is willing to live with.  If he wants it to purr again then do all
the cylinders.  If he needs transportation around town then just do the one.
Also check the other cylinders with the fingernail test.  If you can catch
your fingernail on the ridge at the top of the cylinder (not the carbon
buildup) then rebore the whole motor and he'll have a motor that lasts
longer.  Your fingernail can feel wear of about .005 - .008" (or .003-.004"
per side of the bore).  All that wear is in the top 1/4" of the cylinder
wall.  That's tough on rings to flex out and in that much.  Hope this helps.

Dave Freed  '93 S4

------Original Message-------
From: quk at isham-research.freeserve.co.uk
Date: Tue, 26 Sep 2000 20:07 +0000
Subject: Rebore one pot only?
To: quattro at audifans.com

Has anyone ever tried to repair an engine with _one_ badly
scored cylinder bore by reboring just that one pot?

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



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