Model a distributer help

[peter schmidt]

I just pulled apart my distributer to put in a modern upper distributer plate and install my new style cap wires and put in new plugs. The car was running but ruff and would stall out and miss I compression checked it it has 75 75 77 and 77 psi on the cylinders from front to back witch seems good from what I've read. I also have a fuel problem but I want to get the ignition system up to par before I mess with that. The car has been converted to 12v very poorly so I want to redo all the wiring. I ordered a modern upper plate for my distributer a new lower plate with a extended wire new rotor and the modern style cap and wires I pulled the old cap off then the upper plate and there is no lower plate even in the distributer I'm new to these distributers so I have no clue what's goes where as I have nothing to go by right now the wiring is so bad I'm not gona use it there's splices not covered and all the wires came in through the distributer from the driver side front hole there frayed and exposed with random connections to other wires just bare and twisted together. Does any one have a breakdown of a model a distributer and a wiring diagram for one? I know it's probably a lot to ask but I am lost. Thanks

[Mitch//pa]

here is a link for dist breakdown
http://www.snydersantiqueauto.com/up...view-10152.pdf
the parts supplier books are very informative

[Mitch//pa]

6v pos wiring diag

[Mike V. Florida]

You have changes so much it will be hard to determine what is wrong.

Your compression is good.

Let's start with a short list it check.

did it ever run good on 12v?

Do you have the right coil?

[peter schmidt]

Thanks a lot for the diagrams hopefully I can figure out where everything goes as mine will be a little different with the modern style upper plate. And it did run I don't know how with all that was going on wrong with the distributer I just recently bought the car it never ran great but ran I have a 12v coil on it and it has a 12v alternator but everything is wired so bad. I never got to drive it to far as the sediment bowl kept clogging but that is clean now so I wanted to redo the distributer then rebuild the carb to hopefully get this thing running right but for now I just want my distributer together and working right and I'll go from there. Anyone do a how to thread on installing a modern upper plate on here before?

[jrelliott]

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You may want to check the gap between the rotor and distributor cap connections using the original style distributor cap to see if there is excessive play in the distributor shaft. Will cause erratic running if the gap widths are not close to each other. Cannot remember the exact gap width of the distributor connections. As a suggestion go back to the way was originally and change one thing at a time. Lot easier to figure out just what is causing the problem.
Do not understand your comment that there was no bottom plate in the distributor as this is where the spark advance is controlled from the lever on the steering column.

[peter schmidt]

The part number 13 in the diagram mitch // pa posted the link to was missing from my distributer part number 17 was there the upper plate that the spark advance is connected to what is the bracket for on the bottom of the bottom plate (number 13) doesn't show in the diagram. I would put it back to original and replace a part at a time but I need to redo the wiring under it all and the lower plate was not even in the distributer

[Bob C]

One end of the condenser is mounted to the bracket on the lower plate, the
ignition switch is also connected to the lower plate.

Bob

[peter schmidt]

ok the modern upper plate moves the condencer up there so i guess i dont use the bracket on the plate. what wire should hook to the bottom plate then? the one off the coil? or just a 12v ign source? he has the condensor mounted outside the distributer with a wire going from the coil to the point block pigtailed off to the condensor then had another wire from the starter to the other side of the upper plate on the points. ill post some pics

[peter schmidt]

first two pics are of the new bottom plate that was missing originally


the condencer no longer mounts here as it is now on the new upper plate shown here

here is a picture of the old upper plate

the cloth wire goes from the - side of the coil to the pointblock where it pigtailed off and ran outside the distributer to the condencer (purple wire) in previous pics
the blue wire that came from the other side of the points to out the distributer then connected to turn into a yellow wire to go down to the starter in this pic

i doubt this wiring is correct so how many wires should go into the distributer and where do they connect on eaither end

[montanafordman]

Yikes! Looks like you have a dangerous mess of wires there... You are wise to tear it all out and replace with a new wire harness. I don't understand why people go crazy splicing random wires in when a new harness isn't all that expensive. Sacramento Vintage makes their own harnesses and I've heard people like them the best, I got mine from Snyders and was also impressed and it works great. I don't run a modern upper plate but the pigtail wire from the lower plate connects to the stud on the points, and the armored wire from the ignition switch is the only wire from the outside other than the coil wire to run INTO the distributor.

[peter schmidt]

i think the points should be grounded through the body of the distributer correct? so i should be able to just hook up a new wire to run from the coil to the bottom plate which will go from the bottom plate up to the points. should this be hooked up to the - or + side of the coil on a 12 v negative ground setup?

[Mitch//pa]

12v neg ground system hook up wire to - side of coil to dist

[700rpm]

I have never heard anything good about the new upper plates. They seem to consistently be the cause for ignition problems. I suggest you go back to an original setup, including 6V system and a new harness.

[montanafordman]

Originally Posted by 700rpm

I have never heard anything good about the new upper plates. They seem to consistently be the cause for ignition problems. I suggest you go back to an original setup, including 6V system and a new harness.

Me too.

[peter schmidt]

well anything is better than what was in there if the modern upper plate dont work i can always swap it out.

[Tom Wesenberg]

I can't see enough of the wiring to know how it's wired, but for sure it looks confusing!

Ford had a good basic wiring and ignition system. The coil power comes from the starter switch to the terminal box post on the firewall, then goes through the ammeter and back to the other terminal box post, then up to the coil. The other coil terminal leads to the ignition switch, and from there through the armored cable to the lower plate. From the lower plate through the short wire to the points. Each time the points close they send the ground to the coil so it can build up a good magnetic field. As soon as the points open this magnetic field RAPIDLY collapses and causes high voltage to be generated in the secdary windings, which get sent to the correct plug by the rotor.

If the lower plate was missing, was the spring between the top and lower plate also missing? She spring pushes the top plate against the slots to help ensure a good ground. A missing spring might will leave the top plate loose and might casue missing from a poor ground.

I've found using the original top and bottom plates (with a good fine strand wire on the bottom plate) to be the most reliable ignition system.

Be sure the terminal on the bottom plate wire (that screws to the points terminal) has a 90* bend, so it doesn't contact the cast iron body, nor the spring.

[Purdy Swoft]

I agree with 700rpm . I would switch back to the original setup. The wiring harnesses are not expensive and good wiring diagrams are available. I like the diagram in Brattons catalog on page 92, it is easy to follow. I use the cut out to terminal box harness part number 20500, price $12.05, page 91 .I use the terminal box to dash harness, part number 20350 , price $10.50, page 90. Coil wire to terminal box wire, part number 20260 , price $2.00 page 90 . These wires are all color coded as original and the wiring diagram is easy to follow. I run 12 volt positive ground with the original generator and use the original diagram and original wiring harnesses as listed above with no change. Negative ground will actually be easier to live with if you use the one wire alternator . The coil and ammeter connections will need to be reversed to show a charge at the ammeter and have correct spark at the spark plugs , if you run negative ground. I use the new improved ignition switch and cable part number 16330, price $62.80 Page 72 . Lower cost switch setups are available but use the cheap mswitch that often causes problems. I never use the original pop out switch because it is a difficult connection at the dash and is stiff and hard to work with. Besides that, the original pop out is a closed assembly and a problem waiting to happen. I use Brattons catalog as an example because it is easy to navigate and has good diagrams and info. Many others cary the same good parts but the part numbers will be different. This is really simple and works for me. The modern upper plate setup is a jury rig at best, I've tried it and there is no advantage. The modern set up will cause many model A's to never run again !!!!!!! Hope this helps.

[Tom Wesenberg]

Peter, those hoses in the last picture in reply #10 look like they should be replaced, but save those good original clamps on them. With a sandblast and replate they will look like new again. I've used the Caswell home plating kit to do mine.

[peter schmidt]

looks like ill be switching to the original style upper plate soon or at least redoing my original one. i got to wait a wile to get all the wiring but thank you for the info. the car needs gone thru i will be putting all new hoses on soon but i want to get it running right first its my first model a so i have alot to learn