Re: Finding TDC with a dowel

[Tom Jennings <tomj@xxxxxxx>]

> > Umm, why is finding TDC becoming such a BFD?

On Mon, 29 Nov 2004, Brian Hagen wrote:

> Probably because my timing mark is AWOL.

Oh I didn't mean your problem/discussion, I meant all the
pencils, fingers, screwdrivers, etc, it's all moot since you
just needta find when the damned thing comes up to the top.

And all of those non-finger things won't tell you WHICH TDC!
without pulling the valve cover off, the whole point of the
finger trick is that you don't need to do that messy job just
to find damned ignition TDC.

The dist-cap-off, there was just some tangential mention,
I thought I'd ask the obvious. Nothing else meant by it.

THe following is utterly certain:

* Spark fires the start of the power stroke right when 
a piston is a tiny bit before TDC. 

* 5 degree BTDC is "pretty close" to TDC for initial-set
purposes. The engine will run at zero degrees.

Since the timing marks on the crank pulley (part of the harmonic
balancer) are STAMPED IN METAL it's unlikely they have moved.
The marks on the block end of things are cast into the timing
cover on the "new" (199, 232, 258, ...) six.

* Therefore, you can trust those marks.

Below will get you distributor installed "worst case", eg. you
took it all apart and rotated the damned motor, oil pump and distributor
and don't know where anything is.

CORRALARY:

IF you get the distributor aligned properly, and it will not
start, THEN it is not the problem any more. STOP FIDDLING and
move on to the next thing. 

I know this is a lot of trivia and detail if you're new to
solving these problems, but I can assure you, from personal
experience and in teaching technical problem-solving, it's far,
far faster and easier to go slow, actually figure out what
things are doing, and solve from First Principles. Then you
can help others figure this #$%^ out!

Sputtering and backfiring are usually ignition and timing,
but there are other ignition problems that could do it. Get
this stage right first.



here goes:


Convention is, you install distributor using #1 cyl TDC. It's
only convention, but stick with it.

* Using (whateverthehelltrickyoufeellikeusingbutcantrust!) bring
number 1 cylinder, the front-most on a six or an eight (*), to
TDC, on the compression stroke. Crank to get in the neighborhood,
then turn by hand. LEAVE IT THERE.

The distributor doesn't give a crap which way it's rotated,
it's symmetrical. 1 5 3 6 2 4 1 5 3 6 2 4 ... The only thing
that forces you to pick a spot is the damned vacuum advance unit.
If that weren't there, you could stick it in any old way.

That said, it is nice to have YOUR distributor pointing more
or less the same way as EVERYONE ELSE'S so that you can talk
about it with others without translation, etc and not confuse
auto mechanics who might later look at it, and yourself when
you fail to write it down (you are taking notes, right? :-).



This next is in TWO PARTS: Note that you're actually doing two
things at once: aligning the distributor (vacuum advance) and
the oil pump drive. You will need a really long screw driver,
or a piece of steel brake/fuel line flattened on the end with
which to rotate the oilpump. You can see the slotted shaft
straight down the bottom of the distrib hole with a bright light.

PART 1:
* Put the distributor cap on the distributor. Determine which
is to be #1 wire. Mark that spot -- on the distrib body --
with a marker, paint, etc. Take the cap off, extend the mark
into the distrib so you can see it easily.

* Put the rotor onto the distrib.

* Grab the distrib with both hands. Align the rotor to your mark
with one hand, and guide the distrib into the block with the vacc
advance where you want it to end up, usually around 7 o'clock.

* Note direction and approximate amount it rotates due to the
helical gears.  (NOTE: don't worry about the oil pump here;
don't worry if the distrib doesn't fall all the way to the
bottom, YET.)

* Repeat this step until both the rotor is pointing at the mark
AND the vacuum advance is at 7 o'clock: Pull distrib out JUST
ENOUGH, rotate distrib (keep rotor on the mark), drop it in.

YOu should end up with the rotor on the mark, and the vacuum
advance in a place where there's lots of room to rotate the
distributor, later, when you time the engine.

* MAKE A BIG MARK on the distributor body and the block so that
you can pull it all out and re-do it. YOu might make a second
mark where the distributor rotates to when you pull it out.


Note that at this point it might not fit down all the way into
the hole. There's a shoulder on the distrib body/neck that
rests on the block for the hold-down fork.



Now you have to align the oilpump to the tang on the
distrib. It's not hard.

PART 2:
If the distributor slides allllll the way in down to the block,
you're done! If not...

* With your finger on the shaft so it doesn't rotate, pull it
all the way up and out. Try to guesstimate the position of the
tang on the end of the shaft.

* Rotate the oilpump (with the long screwdriver) to match. Insert
the distributor. Lift, rotate, insert as before to get it
pointing the way you worked out earlier.

* You may have to repeat these steps of part 2.





* The two V8 banks are NOT identical. If you lean into the engine
compartment, you will see that one bank is slightly closer to
the front of the car than the other. About 1", or the thickness
of the big end of the connecting rod. The closer-to-the-front

one is the odd numbers, eg. #1 is up front.