Tune up

[treed2 at wsu.edu (T. Reed)]

On Fri, 5 Mar 2004, Brian Wagner wrote:

> Ha, Brian you are wrong on the inter-cam timing chain. There have been
> more than one lister that has changed or needs to change this part, I am
> one of them and I did it after cincy last year. Yes they rattle nasty
> like.
>
> I even video'd what a bad one looks like with a 1/2" of deflection, not
> good for overall timing. This part should be replaced every 100k to be
> on the safe side, mine was at 165K. And yes get this chain from a
> reputible VW parts supplier, the rest of the stuff you are right on.
>
> Brian

Indeed. There was a surprising amount of play in that video..

Anyway, it makes my curious brain wonder what the effect of this slop
would be on cam timing. Obviously the exhaust cam would not be affected as
it is driven off the timing belt.. but the intake cam timing would be
retarded or advanced. Err.. actually probably both, or just totally out of
whack because the rotational forces from the cam lobe are sinusoidal-ish,
and there are 8 lobes per cam, all out of phase pairwise. Meh.

I'm curious what drivability effects you noticed before/after replacing
this chain.. seems to me this could be something of a tune-up item with a
high mileage head. I know first hand just how much of an effect one
timing belt tooth off can have on your engine. Something like this could
concievably account for variations between otherwise identical setups.

-Toby