You may want to review why
advance is needed by reviewing this page.
I find that the advance
curves that came on almost everything made during the "points" era to
be lazy and not at all optimized for the kind of performance I expect. During
my younger days, my family obligations and financial situation made buying
expensive bolt on equipment out of the question, and therefore I turned to
carburetion and ignition modifications to satisfy my hot rodding urge. I found
that this area of hot rodding is generally overlooked by most folks, and that
there is a satisfying degree of performance (both in power and economy) that
can be gained by the average joe who is willing to spend a little elbow grease
to solve the problem.
With regards to the Y and
its distributor, the more initial advance you can run without ping, the
snappier your car/truck will accelerate. The more load that your Y block must
pull around, e.g., if it is heavy or you tow or haul loads with it, the less
aggressive you can be in adding advance, and the less improvement you will see.
On the other hand, many Ys have relatively low compression, which helps quite a
bit in how aggressive you can be in speeding up the advance curve.
There are two designs of
Ford distributors. the newer kind has weights that look somewhat like
triangles. This kind is probably a little easier to modify with regards to
limiting the amount of advance in the distributor itself. However, I can't say
whether or not Y distributors are of this type -- they were coming out with
this type about the time the Y was removed from production. I don't know
whether Y distributors were made to this design or not. I mention it because it
may be the way to go if they exist.
The older kind is the one
I'm talking about here. This kind has two large cast weights underneath the
breaker plate that look a little bit like fat commas.
What you need to look for
in this kind is that the pins of the weights, the pins that ride in the slots
of the point cam assembly, are not worn. These pins are made of hard steel, but
they will get groove worn in them from the pint cam assembly slots over years
of operations. It took me going thru about 10 units at the junk yard before I
could come up with a pair of weights with good pins. IF the pins are worn, they
will fit the slots in a sloppy manner and give you an erratic advance curve, so
watch this.
First, you should figure
that 36* to 40* of advance, total (but figured without vacuum advance -- more
on that in a minute) would be what you want. This is the combination of
mechanical and initial advance, measured on the crankshaft. I like to run 17*
initial and 37* total advance on my F100. This will make your machine pretty
snappy off the line and perform well around town.
The point cam assembly
controls how much advance is in the distributor. Typically, you will see about
26* to 30* of advance, measured at the crankshaft, in a Y distributor. This
amount is controlled by the slots in the point cam assembly that the pins of
the advance weights ride in. What you want to do is limit this amount of
advance, and big truck Y distributors do this. Mine, for instance, has 20* in
it. This is close to being ideal. The alternative would be having someone braze
up the slots for you and then using a small rat tail file to lengthen the slots
until you get what you want.
You can use your engine as
a distributor machine. Just measure around the damper with a fabric tape for the
diameter of the ring, and divide this figure by 36. This will give you the
distance around the ring for 10*. You can use a small triangular file to make
marks that will be easily visible with a timing light, especially when you put
a little chalk in the groove. Using a tach and a timing light, you are set to
figure out what advance you have at any rpm.
The springs control how
fast the advance comes in, compared to the rpm. One spring is loose and heavy,
and the other is light. The light spring controls the advance at the lower
speeds, and when the weights are farther apart at higher rpm, the heavy spring
slows down how much advance will be added as engine rpm climbs in the higher
ranges. Look to have all of the distributor's advance in by 2500 to 3000 rpm.
The exact point is the one that is near, but before you get pinging. This will
depend on how heavy your rig is, so you do have to spend some road time testing
how you have everything set up. This can be tedious, but it is the alternative
to giving someone big bucks to give you what they think will work on your car,
as opposed to something you have customized for it.
To work on the vacuum
advance, use a Mighty Vac to provide a given vacuum setting. Then you can use a
timing light to figure out how much advance you are getting at a given manifold
vacuum level. Again, you want to bring in as much as you can as soon as you
can, but you are limited by the car's weight for the total the motor will
tolerate. You have to experiment. In general, you will want a vacuum advance
unit that will give you about 10* to 15* crankshaft advance. (Remember to pay
attention to "crankshaft advance", because it is double the
distributor advance, e.g., 10* of distributor advance is 20* of crankshaft
advance.)
There are two kinds of
canisters: the old kind can be taken apart and, by putting in various pieces of
tubing, you can govern how much vacuum advance the canister will allow. But you
have to change the spring in order to change the rate of advance, or how much
advance you will get at any given level of vacuum. The newer canisters will
allow you to change this rate by adjusting the spring tension, but you cannot
take them apart to change the total amount of advance. You change the tension
by inserting an Allen wrench in the spigot of the canister and turning a set
screw inside.
Once you are set with the
initial and mechanical advance that you have tested on the road, hook up the
vacuum advance and begin to test it by driving in a high gear and low speeds, so
that the vacuum gage (you NEED one of these, too!) is reading high. Then,
accelerate briskly (and without downshifting) and listen for pinging. You want
to be just below the ping point in all driving situations.
I have found that most guys
will eagerly bolt lots of high dollar stuff on their car, but neglect to get
all the performance they've paid for by tuning their ignition and carburetion,
and this is especially true for street driven rigs.
I hate sluggish performance
and flat spots, and will not tolerate a car on the street that backfires. (I
often hear fellows complain about Holley carbs, because the power valves can
blow out when the motor backfires. Their solution seems to be getting a
different carb. Mine is to not have a motor that backfires in the first place.)
When I step on the gas a slight amount, I expect an immediate increase in power
commensurate with the amount that I stepped on the gas. People who drove my
cars always noted this, and one of the faster ones, my wife didn't like to drive
because she considered that the throttle was way too "twitchy",
especially after she scraped the fender trying to drive it into the parking
space. I found that folks who didn't prepare their rig often could be
embarrassed, even when they had the potential to win the "argument".
I never wanted to fall in that category!
What I have described to
you is pretty simple, but it depends a bit on a basic understanding of what the
engine wants in terms of advance, and why. It took me a couple of years to get
good carb and ignition tuning down so that my engines would run well. What I've
written here will get you down the pike a little quicker, but it will still be
work. This is the kind of stuff that is a barrel of fun to do, because it
doesn't cost much, but other guys always wonder why the car runs so well. The
thing they never understood is that this can be mastered by someone who is
persistent, thoughtful, and careful in their work. It isn't secret or rocket
science.
Expect some failures and
disappointments. You won 't be able to do it over a weekend -- it will take you
some time to get it to work right for you. But when it does, it is sweet,
especially the feeling of having done it yourself.
This page was last modified on 21 July 2004