Distributor drive gears

[Jack Bowser]

Does anyone know if new distributor drive gears are available anywhere?

I don't see them on Mark II Enterprises. Only the tach drive gear.

A good friend who is very knowledgable about engines etc, saye he can build me a new distributor that will vastly improve the engine performance.

These double vacuum distrubutors were not very good to begin with which is why Ford went away from them.

A new distributor will also allow a change of Carburetor if I ever want to do that.

Since these distributors were designed to work specifically wiith the Holly Carburetor, changing the Carburetor is not easily accomplished if this distrubutor is still in the picture.

[Mark Norris]

Does anyone know if new distributor drive gears are available anywhere?

I don't see them on Mark II Enterprises. Only the tach drive gear.

Here are a couple of pictures of the driven gear for the distributor shaft;

20598 20599

Its part number 12390 and has 15 teeth on the gear.

They come up on Ebay occasionally as NOS which is where this one came from.

[Jack Bowser]

Thanks, Mark.

my friend made some TP calls and located one.

[Jack Bowser]

We just found out, The hard way that the gear we located has the teeth cut in the opposite direction because it is for the truck version of our engines.

Ford replaced the timing chain in the trucks with gear drive which necessitates the cam to rotate in the opposite direction so the distributor drive must be the opposite cut.

Some trivia for everyone.

[Jack Bowser]

Mark, This part number might be for the truck version of the gear.

I hope to have the correct gear coming so I will post the number if it shows it.

[Egenolf]

Hello,

Mark is right, the exact part number is FAB 12390 C (15 teeth).

[Mark Norris]

We just found out, The hard way that the gear we located has the teeth cut in the opposite direction because it is for the truck version of our engines.

Ford replaced the timing chain in the trucks with gear drive which necessitates the cam to rotate in the opposite direction so the distributor drive must be the opposite cut.



I'm not sure sure thats right.

Our car 368 Y-blocks are timing chain driven so the cam shaft rotates in the same direction as the crankshaft. I have no idea if they used gears instead on the truck versions such that the camshaft rotated in the opposite direction but if they did it must have caused real havoc with the oil pump.

A picture in the ignition section of the official Mark ii manual shows the distributor with the same driven gear teeth orientation as the part I posted (ie. viewed from the front surface the teeth slope right to left from top to bottom);

20609 20610

The distributor driven gear to my recollection "rests on top" of the camshaft driving gear;

20611

Naturally the driven gear is positioned 90 degrees to the driving gear. The teeth on the camshaft are shown on the above diagram to be sloping left to right from top to bottom and hence meshing orientation is correct for the rear surface of the driven gear.

Since the crankshaft rotates clockwise (when viewed from the front of the engine) then the camshaft rotates in the same direction. This drives the distributor anti-clockwise as designed.

As far as I can tell the driven gear part in the photo is correct.

...and what do you know here's one NOS on Ebay (FOMOCO FAB 12390 C at $99), worth double checking its ID vs. the distributor shaft OD;

https://www.ebay.com/itm/NOS-1963-1964-1965-1966-1967-FOMOCO-406-427LR-427MR-DISTRIBUTOR-GEAR-FAB-12390-C/203072456396?epid=1423245199&hash=item2f480fc6cc:g:FgMAAOSwokBfMEfX

[Egenolf]

Here is a picture of my 56 distributor gear drive:

20612

https://up.picr.de/39196795xi.jpeg

[Mark Norris]

Thanks Holger, thats the definitive picture.

[Jack Bowser]

Thanks for all the responses that help.

I think I have the correct gear coming now so I will be able to put it on my old distributor to Save in original condition.

Today we removed the gear from my original distributor and installed in my new HEI distributor that is now installed and running my car beautifully. My off idle stumble is now gone so it was the distributor and not my carburetor

I hope I’ve downloaded the correct pictures.

[ATTACH=CONFIG]20613

[Jack Bowser]

With the distributor drive gear cut correctly with the cam going the other eay, the distributor will rotate the correct direction and the oil pump will be turning the correct direction.

[Milsteads Garage]

I have had this problem. I had a customer years ago with a 57 premiere that wouldn’t start after installing a new distributor. It turns out the distributor had the wrong gear which was 15 teeth. The distributor needed a 16 tooth gear and of course I broke a tooth off the gear moving it to the new distributor. How I ended up solving the problem was installing a drive gear from a 352 FE engine.