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Re: 20v (RR/3B) valve/piston interference

Phil -
    The 3B is an interference motor (bought mine with a complete matching
set of bent intake valves). I am not sure whether the interference is
dynamic or static..........though if the valves floated enough to cause
dynamic interference in an otherwise non interference motor, I doubt it
would have made it to production. Probably just off the mark a bit, enough
to cause an ignition timing issue, not enough to cause an interference
problem. The T belt drives the exhaust cam, which in turn drives the intake
cam via roller chain. Unless he removed the cams from the head, the
intake/exhaust cam relationship should not be an issue.

Tom Nestor

>I'm going to a Club member's house at the weekend to take a look at a
>20V that won't start.
>He's changed the timing belt himself - I suspect without access to the
>proper tools - and now the car refuses to start.  My obvious first
>suspicion is crank/cam/distributor misalignment.  I'm interested in
>BTDTs about the following:
>a) The engine has been spun on the starter.  Is the 20V normally
>   interference-free at low revs or would this (if one or other
>   of the cams was way out) inevitably lead to interference?
>b) How noticeable is valve/piston interference if it does occur?
>   I'll be doing a piston top inspection using a Bend-A-Lite down
>   the plug holes.  Still haven't bought that endoscope.  Do 20V
>   valves contact flat and leave no mark, or do they go in at an
>   angle like the 10Vs and leave big dings?
>c) How safe is hand turning to realign - which to turn, the cams or
>   the crank?
>The ECU is currently out of the car, so its non-volatile memory isn't -
>no hope of pulling 'the story so far'.  I don't really want to spin the
>engine on the starter (even if the owner claims to have done so already)
>unless I'm sure of the mechanicals.
>And yes, if I get a chance, I'll be checking his torque.
> Phil Payne
> UK Audi quattro Owners Club
> Phone: 0385 302803   Fax: 0870 0883933