Distributors - I'm kind of stumped

duo_z

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Jan 24, 2009
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Ok, I'm wondering how I go about choosing a distributor. Am I making them out to be more complicated then they are? Is there some formula to it? I've got a 289, slightly modified but still running stock heads.
 
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Duo Z; IMHO From what you described, almost any distributor will work with your current set-up. choosing one is really a matter of preference, more than necessity, although it is necessary to have one. That being said, there are really two tasks that a distributor handles. The first is to break the current going to your Coil, allowing it to create a powerful discharge of electricity! Points are nothing more than a common switch, that are held closed by a spring, and opened by the small cam lobes on your distributor shaft. Before electronic distributors were available, single points proved to be unreliable, in High Perf. motors, due to the Higher RPMs that were generally associated with their use. It was common for single points to float, or cause inaccurate timing at the higher Rpm's, so one way of fixing this issue was to go to a Dual point distributor. The dual points worked in unison, which allowed them to share the workload, which enabled the desired results. Then came the "Electronic" distributors. They proved to be more maintenance free, and generally more reliable, than points...... until they break. Diagnosis of a problem, can be much simpler with points, due to their simpler design. this is why so many people are still fans of the old points system. When you start looking at electronic distributors, there are basically two types. Plug and Play, and those that require an "External" control box... examples of these are seen with "Duraspark" and anytime you see something like a MSD box being used. Plug and Play examples would be like a "Pertronix" type set-up. The second job of a distributor happens after the Coil has discharged it's momentary jolt of electricity. The power from the coil surges through the High Voltage cable, to the center terminal of the distributor cap, where it is rerouted to the Cylinder that needs ignition. This happens when the power is "Bridged to a corresponding terminal, by the rotor, allowing the voltage to leave the cap, through that spark-plug wire, seeking "Ground" at the plug, where it creates an Arc, while grounding. So......I hope all of this makes some sort of sense, and helps clear up some confusion, in making your choice an easier one. FWIW.... I'm currently installing a warmed over 289 in a project, and stuck with the same dilemma! Too many choices.... but I think I'll try a "Pertronix II" distributor, in this one....... Good Luck with your Choice! and if I've misstated anything.....I'm sure others will chime in, and help you sort this out.......
 
I currently have no distributor to use, so in your opinions what would be my best route. Should I look for a used stock one, a Summit stock replacement, an aftermarket upgrade? Also what does curving to match mean?
 
In all my Mustangs, both SB and BB, I used a stock distributor with faster springs, and then did the electronic conversion, though I used the Unilite. Also add a stronger coil, quality 8mm wires, and you'll be good with a mild motor. And, it will still look kinda stock, and if the electronics fail, you can easilly toss the points back in and get home.

In my Cobra, now a full race car, I run a 360 HP Roller 5.0 motor. For a ditributor, I use a fulll unilite distributor as a trigger, and run the system with a Crane HI-6 box and coil. The nice thing with the Crane box is that you can set the rev limiter right on the box with a small screwdriver. If you go with a box, make sure you give it a full 12V+ power source.

It may even pay to bypass the resisitor wire in your Mustang if you take out the points, as the resistor wire is there only to try to reduce points arcing. Any Electronic system loves full voltage.
 
I currently have no distributor to use, so in your opinions what would be my best route. Should I look for a used stock one, a Summit stock replacement, an aftermarket upgrade? Also what does curving to match mean?

Hi,

In answer to:
"Should I look for a used stock one, a Summit stock replacement, an after market upgrade?"

A good used dizzy (distributor) is perfectly fine. As long as, it has been cleaned, and any suspect wear items replaced. This is, usually, for those wanting to stay more period correct or have one laying around. I have been running a "period correct" in my highly modified engine for many years with total success. I have run the Mallory Unilites (after-market), as well. Why did I change? Only because I didn't like the "red" cap! Although, I think now you can get them with a black cap. However, even new, I had it checked out to determine it's "curve" rate, it's stability, and custom curved (explanation later). It had electronic points.

A Summit or after market distributors are, typically, OK and easy to find. I,as others, will advise, get an electronic version without points. Installing it, requires another set of skills and knowledge.

Regarding "curving to match";
This is a reference to how ignition timing advances relative to engine RPMs when accelerating. There is a specific correlation between the two. "Curving to match" can be viewed in a couple of different ways. The simpler version is, there are certain bench mark degrees that should be attained as engine RPMs increase.
For example, at idle an engine may require 10 degrees of advance, at 1500 Rs, 12 degrees, so on, up to 3400Rs with a total of 36 deg. The act of making sure your dizzy attains the benchmarks, for which it was designed, can be construed as "curving to match" from a stock perspective.
However, in the interest of performance, "curving to match" can take on a whole perspective.

I hope this clarifies without confusion. What might seem a simple question can open a "Pandora's box".

Happy Motoring!
 
I like the advice so far. One more question then. Is there a difference between an early 289 and late 289 distributor? I don't mind doing a little refurbishing on an old one, and I can alway upgrade later. But I'm not sure if I can just look for any 289/302 distributor, or if I should worry about it being early 289 specific.

P.S. Also is there a better points/electronic upgrade kit to go with or are they all pretty equal?
 
I like the advice so far. One more question then. Is there a difference between an early 289 and late 289 distributor? I don't mind doing a little refurbishing on an old one, and I can alway upgrade later. But I'm not sure if I can just look for any 289/302 distributor, or if I should worry about it being early 289 specific.

P.S. Also is there a better points/electronic upgrade kit to go with or are they all pretty equal?

Hi,
Within the 289/302 era, I don't think there is a big difference per se. The choice is how you put it all together. First, you start with a solid working equipment, I.E. mechanically perfect. The next attribute, is the curve you choose for your engine's dynamics.
Points vs. electronic switching, I'd (have chosen) choose Pertronix. Installed properly, more precise, & no maintenance.
In my opinion......it works well!
Happy Trails,
 
I put a Duraspark in my 302 partly out of convenience; I needed a roller-compatible(steel gear, not iron) distributor for a carbureted engine, so I got an '85 Mustang GT 5-speed unit and coupled it to a $20 GM HEI module. The same distributor is actually easier to find with an iron gear for flat tappet cams like 99.9% of the 289s out there would have.
 
Depending on your cash flow:

I highly recommend the Crane digital billet distributor and their Hi-6 ignition box and coil.

The distributor belongs in a museum. I slept with mine for a week before installing it......drop dead gorgeous!!!!:nice::hail2:

The beauty of the distributor aside from being made of billet aluminum and having very nice optical trigger and using a gear that is compatable with ANY cam material, is the fact that it has 3 vacuum advance curves (has built in MAP sensor) as well as 7 different mechanical advance curves...all set with a simple screwdriver twist to the dials.

The Hi-6 ignition box has a rev limiter built in that is adjustable again...with a simple turn of a dial.
 
At the moment the build is mostly stock. I've got a High Energy cam kit, and AirGap intake. Other then that the rest is stock. Stock heads, carb, rotating assem. (polished rods). I do plan on changing out the heads after the car is finished, but right now I'm just trying to keep it cheap. I have only been upgrading things that need to be because they are either worn out or missing. I don't think I will ever be going insane with this build just because of the rotating assem. being stock. So a distributor that I can have a little fun with is not a problem. And while I don't want to spend a lot at this point in time I still need a distributor. I don't mind going over price a little to get something worth it. If its going to cost me $300 to buy and build a stock to the way I want it, and $350 to buy an aftermarket upgrade, I'll just get the upgrade. But if its going to be a couple hundred $'s more, I'll just stick with the stock for now. Thats why the heads are stock at the moment.
 
I would go with the duraspark distributor. As distributors go, there is nothing wrong with them and it will work great for what you are doing. You can provably get a duraspark setup from a forum memeber here for under 100 bux. I sold a duraspark dizzy to another forum member for 45 bux a few years back. I didn't have the ignition box.
 
The stock single point dizzy distributor was a hassle for me cuz it wasn't easily adjustable. Had to send to someone with a distributor machine to get it recurved. I went with a dual point Mallory vacuum advance dist which is totally adjustable DIY at home in the garage. Simple, inexpensive, no special wiring needed,has a steel gear. Drop in, use the stock coil if you wish. The Mallory upgraded coil gives a hotter spark. Use stock wires. Set the points and you are good to go. You can buy a set of springs to change the advance curves to get maximum perf. The vacuum advance curve is adjusted with a allen wrench. Once you get some experience with an adjustable point dist. you can upgrade to electronic anytime. However, the electronic requires wiring changes because it needs full 12v power. The multi spark discharge MSD set ups are also an option and can be used with a point type or electronic dist. Remember the KISS principle . Keep it short and simple. Good way to start before getting fancy and complicated.