Re: timing belt

[Luis Marques <marques@raytheon.com>]

I have said this before and I will say it again: the timing mark on the
harmonic balancer (pulley) is absolutely and complete useless when
indexing the camshaft.  You never know if somebody has messed with it
before, or how accurate it really is.  Better to go by the marks on the
flywheel.  Those are 100% accurate if combined with the
stick-thru-the-spark-plug-hole trick.  Turn the engine by hand and when
the #1 piston is up (stick is highest) and the "0" flywheel mark align
(and the cam lobes on #1 point up), you have TDC for sure!  Don't try
this unless the timing belt is still on as you could bend valves on
interference engines.  Be careful that whatever you use as a "stick" is
long enough, doesn't break in the cylinder, or scratches it.  Also make
sure the "stick" (or screwdriver or whatever) moves freely and doesn't
bind diagonally as the piston goes up.

If you have a spare set of helping hands, one of you can turn the engine
slowly while the other looks for the TDC marks on the flywheel and
bypass the insertion of foreign objects into the #1 cylinder.  Once the
engine is at TDC, you can double check the mark on the cam sprocket in
line with the top surface of the head, so that you can see it thru the
little opening on the rear timing belt cover.  After everything is put
back together with the new belt, take it for a test drive.  If the
powerband feels fine, go have a cold one - you are done.  If it feels
very strong in the bottom and weak at the top or vice versa, you missed
the cam timing by a tooth.  One little trick I like is to mark the old
timing belt, cam and crank sprockets, and then transfer the marks off
from the old belt to the new one.  When you put the new belt in, you
simply index the marks you just made.  This lets you keep the same cam
timing you had previously independently of where TDC really is.  Don't
forget to check the ignition timing afterwards.  HTH

Luis Marques
'87 4kcsq


> Sachelle Babbar <sbabbar@iris.nyit.edu> wrote:
> 
> How does the timing mark go so far off? Made incorrectly? My old turbo
> had about 1/5 of a turn off. I was told that this was not enough to
> cause interference. I'll be doing my timing belt in a few weeks, so I
> need all the help I canm get.