Timing The
Ignition
By Marcus Chick
This could be a
continuing argument; however, I have noted that there are several variations on
the theme of timing the six cylinder engines. As many will be aware, there are
several engines and even more distributors.
It would appear that
information relating to the Low Compression engine is vague and I have only
found it in a Factory “Special Supplement”. A clear date of issue is not clear
as the covers of it are missing.
What it does make clear
to me is that the methods described in many OEM and genuine manuals will lead
to a low compression motor being “mistimed”.
I make this comment on the basis that virtually all of the manuals /
service manuals refer to the timing mark on the crankshaft pulley being 8°
B.T.C. The low compression Motor needs
to be 4°, as do some of the High compression engines, at times (refer below).
I have taken some of the
info from a method & added comment in italics
where I believe information is missing, or perhaps too vague.
Timing the ignition:
Before adjusting the
ignition, identify the engine compression ratio by the letter on the manifold mounting
pad; 'H' for high compression, 'L' for low compression.
Check the fuel octane
rating. I.e. Know what is
going in. Low octane fuel is now virtually non existent. The current Australian
System is neither, R.O.N or M.O.N the latter being noted on aircraft fuel eg 100/130 which relates to its characteristics. Rich, or
lean and is important where boost is used.
When the No.1 piston is
on the compression stroke and the notch on the crankshaft pulley aligns with
the timing mark on the timing cover, the crankshaft is at 8° B.T.D.C.
NOTE:
All high compression engines (8.3 : 1) using a fuel of 95 octane and higher must have a
static advance setting of 8 ° All high compression engines (8.3 : 1) using a
fuel of between 88 and 95 octane must have a static advance setting of 4° All
low compression engines (7.0 : 1) using a fuel below 88 octane must have a
static advance setting of 4° .
Adjust the Vernier control so that the fourth line on the timing scale
(counted from the vacuum diaphragm housing) is in line with the edge of the
distributor body. (That is often a bigger line)
· Turn
the crankshaft until the number one piston is at the end of the compression
stroke and the timing mark on the crankshaft pulley coincides with the timing
pointer on the timing gear cover.
· In some data no mention is made of
removing the distributor cap here. Also of note is the reference to “If the
distributor has been removed”.
· The Drive from the oil pump is
offset so that it can only be meshed one way with the distributor drive The
largest “D” that is formed on the gear will be pointing at approx 45 °
away from and towards the rear of the engine.
· In some data it then tells you to
replace the distributor cap here. Quite useful for next step. As you need to
establish where No one lead is. Often the body of the distributor has a line on
the edge of the body where the cap sits, indicating Nr1 and the cap wires
should be arranged in firing order, with reference to this point.
· Loosen
the distributor clamp bolt and turn the distributor housing so that the rotor
is facing the number one spark plug contact and the breaker points are just
starting to open. (This is “static”
timing) You may also have to loosen one of the bolts on the distributors
mounting flange to allow the clamp to expand.
· In
order to obtain accurate adjustment, the use of a 12-volt test lamp is
recommended; the test lamp should be connected to the primary terminal on the
distributor housing and a good earth. With the ignition switch turned on, the
test lamp will go on at the moment the breaker points start to open.
· Tighten
the distributor clamp bolt and check the adjustment with a neon timing light
with the engine running. *Read following:-
This is the point where things seem to go awry. What is
said in “the supplement” is quite significant.
At the ...“set the Vernier to
the fourth line”... step. The supplement makes a note “That where a special Low
Compression head is fitted to the Six cylinder engines, re-set the timing mark
to the third mark to give an initial setting of 4 ° B.T.D.C.”
This, to me, says that if you do that and set the timing, by
timing light, it’s going to end up back on 8° B.T.D.C.
I would consider when, using the timing light, you would
put the scale on the fourth line. Set it there, and when you have finished,
move the Vernier to the third mark.
That may not end up being the final point, as with changes
in fuel, “the higher the octane the slower the burn” and the timing may have to
be moved toward 8° B.T.D.C. To compensate.
Marc
Disclaimer: The advice
and guidelines given in these articles are given in good faith. The owners
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take no responsibility for any injuries or loss sustained while carrying
out the described tasks and procedures or any consequences arising.
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