the "0" on the flywheel

[SJ]

Couple of tricks to finding accurately the "real" TDC

1. Find compression stroke for cyl #1
Find #1 plug wire on Dist Cap, take off cap
Turn engine till rotor lines up with #1 plug wire position on Dist. I think
dist has a mark for this.
Back off engine, put finger over spark plug hole, turn engine in correct
rotation, verify you have compression

2. Back off engine
- place measuring stick, dowel, whatever into sparkplug hole and let it rest
on piston top
- turn engine by hand, go past TDC(stick goes up and then down) and turn
engine backwards  . .make sure measuring stick does not bind
- Back off engine

3. Find or make a reference point for the measuring stick
- piece of sheet metal (tin can)bolted to valve cover stud will do the trick

4. Locate visual TDC
- rotate engine till measuring stick stops moving
- Mark Vibration Damper Pulley so you can get back to this visual TDC
reference later

5. Back off the engine
- rotate engine in correct rotation till the mark you placed on damper is
about 1 or 2 inches before the reference.
- Put a new mark on the vibration damper pulley
- mark the measuring stick where it intersects the reference point (see 3
above)

6. Turn engine in same direction while watching measuring stick rise to TDC
and then start to descend
- turn engine very slowly till measuring stick aligns with the mark you put
there at step #5
- Put a new mark on vibration damper

7. You have 3 marks now on vibration damper - BTDC, TDC, ATDC
- measure distance between the two outside marks using a flexible or cloth
tape
- put new mark at the half-point of the measured distance
    This Mark is your Actual TDC

IMPORTANT NOTE:
You must eliminate any slack(play) in the system to get accurate results.
You always have to start at the "end point of slack".
Always make all measurements by backing off the engine and then turning
engine in proper direction. This puts all engine components at their one
'end point of slack'.
All measurements are taken by backing off the engine and then rotating
engine in normal rotation  - this eliminates any error due to slack(play) in
system.


If you have too much time on your hands and dont know what to do, you can
finesse this to get a more accurate reading of TDC.
Once you have found TDC per above instructions, you can now use the
hydraulic pump pulley for a more precise TDC location. The hyd pump pulley
is smaller than vibration damper pulley so it turns maybe twice for every
rotation of the damper pulley. In other words, the hyd pump pulley has more
resolution than the damper pulley.
1. Place damper pulley on TDC mark you found before
2. Mark hyd pump pulley for visual TDC - make yourself a reference point
that is over the hyd pulley and almost touching it
3. Back off engine until the measuring stick in spark plug hole goes down
below the BTDC mark on stick.
4. Rotate engine in correct rotation till measuring stick BTDC mark lines up
with reference.
5. Mark hyd pump pulley where it intersects with hyd pump pulley reference
mark.
6. Rotate engine in correct rotation till you go past TDC and the measuring
stick mark again lines up with the reference.
7. Mark hyd pump pulley
8. Measure distance between hyd pulley outside marks
- halve the distance
- mark pulley

You now have a more accurate, but temporary, TDC reference on the hyd pump
pulley.
You can now compare the three TDC marks(damper, flywheel, hyd pump pulley)
against each other.

SJ
85 Dodge PU, D-250, 318, auto
85 Audi 4k - - sold but still on the road
88 Audi 5kq
90 Audi 100q




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