Tuning Y Block Distributors at Home

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