[Vwdiesel] Timing belt

Sat Oct 16 01:13:21 EDT 2004

Sandy.
in defence of doing it the right way....

Now why would you want to time the cam?
Why futter around loosening the sprocket, use up a valve cover gasket, maybe
even have it leak after, use the cam lock plate and spacers, fiddle about
timing the pump, reinstall the valve cover... etc etc...

Okay, because it is virtually impossible to make belts EXACTLY the same
every time. Bear in mind there are  a few different manufacturers as well.
So what happens when you go through the timing process, and why are there
all the steps?

Okay, first off, it is to get the cam and the crank in the exact same
position.  All else does not matter at all. That is all you are doing with
the first step, get the crank exactly at TDC, and the cam at TDC.  this is
done by eyeballing the timing mark on the flywheel to the timing mark onthe
bellhousing, and locking the cam with the locking plate, using feeler gauges
of equal thickness on either side to space the cam tool so it is exactly in
the same plane as the valve cover sealing surface.  Why do this?  It is an
interference engine. Exactly how much can you be off before parts that were
not designed to hit one another do so.  You just don't know. You can guess,
but you don't know.  Retarding the cam in relation to the crank should give
a bit better low end, but on your interference engine, not too much now or
expensive noise issues forth...
Why the cam sprocket is loosened is to let the new belt have the crank at
tdc, and the cam at tdc, and be tight.  Ah, but the lock pin in the pump is
there, and is a third link in the chain.  Not really, because the pump pin
is there to just keep the pump near tdc (take the pin out sometime with the
belt off and see why the pin is in there), and can in fact move a few
degrees back and forth easily enough with the pin installed. The pump is
timed after anyway.  now with the belt tight, crank at tdc, you lock the cam
sprocket to the cam.  Remove the pump pin, and time the pump, because it is
out of spec with the rest of the system.  You can hillbilly tune it or use
the dial gauge, but it will not be ideal usually. Not to say it will not
run, it may run fine, and it may not.  I have never seen an engine run
really poorly (undriveably so) after a belt change before the pump was
timed, but timing it always made it run better. Always.  Optimum results
happen from optimum procedures. I have seen the broken shiny bits that
result from a botched t-belt install as well. Not cool.

I actually install the belt same as you, with the belt going on all pulleys
and tightener at once too.  I find that the easiest way, especially with the
cam sprocket bolt a couple turns loose.

You could just mark each sprocket and belt, and count belt teeth,
transferring the marks to the new belt, as all belts have exactly the same
number of teeth.  This does not in any way account for variability in belt
length either, and there is variability.

There are no attendant tight bolt or cam sprocket problems if approached
correctly.

do the job right, or you will need to fix it.
-James

-----Original Message-----
From: vwdiesel-bounces+jhsg=sasktel.net at vwfans.com
[mailto:vwdiesel-bounces+jhsg=sasktel.net at vwfans.com]On Behalf Of Sandy
Cameron
Sent: Friday, October 15, 2004 5:53 PM
To: vwdiesel at vwfans.com
Subject: [Vwdiesel] Timing belt

The above subject, according to Hagar's suggestion about headers for
searching digest.

I have done 2 belts this year so far, and 2 more to do.

1st was on an NA on the work table in the shop, so easy.

I set everything for TDC, shoved the 11mm long socket in the pump sprocket
hole,
Cleaned the back plate at the top of the cam sprocket, and with a q-tip (r)
dabbed a dot of yellow paint on the top sprcket tooth, and the back plate
right behind it.

Zipped out the 4 crank pulley screws, removed them, then the lower belt
guard.
(The WP pulleys were already off, more about that later)

Removed the tensioner nut, and slid the belt off the upper sprockets, no
problem.

installed the new belt around the crank sprocket, slid the new tensioner
part way on to the bolt. With the belt laid against the tensioner, I had no
trouble starting the belt on to the cam and pump sprockets. Slid them across
the sprockets, along with the tensioner on its bolt, Checked all timing
marks, job done.

My tension calibration is to tighten it to the point where it is just
possible to move the belt back and forth on the pump or cam sprocket a
little with thumbs and fingers. it will only slide about 1/8" before
tightening up. This assures me there is minimum allowable side thrust on the
pump shaft.

Note that I did not remove the cam shaft cover, with its attendant gasket
problems

The engine ran beautifully, and the change in "knock" with the cold start
advance lever assured me the micro-timing was OK.

2nd one was in-car, last week. Could not get the &%#@$* water pump pulley
bolts out

Wit all the above marked, loosened, etc, I was stuck with the lower belt
guard held in place by the WP pulley and no way to get it out..

With a few minutes of fiddling around, I was able to position the belt guard
so the belt would come out without taking the guard right off. It slipped
out over the C-shaft bolt, and the new one went in the same way.

I had no problem getting the belt on the other 2 sprockets using my "both at
the same time" method.
Once again, making sure the cam sprocket was carefully marked before
removing the old one, and checking everything before sliding the belt on, no
timing problems, and it runs and sounds fine.
Once again, no need to uncover or time the cam.

Having licked the water pump pulley insanity, And bypassing the cam timing,
with all it's tight bolt problems, timing belts are now "easy"

While I will not argue the necessity of "micro-timing " the pump with the
dial indicator, I have found that if it is timed right to begin with, it
will probably still be timed right after the belt change. Being lazy, and a
fan of "IIABDFI" (if it aint broke, dont fix it), this works for me.

Having done head gaskets on 2 friends cars in the past, I have got past the
timing belt paranoia, and it's just another little job to be done from "time
to time" {:-)

Sandy

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