[patrickt]

Originally Posted by wrench87

... i guess i will run the mallory gear and just keep an eye on it

Whether you go with steel, bronze, or composite you might be interested in this factoid on Mallory roll pins by RobbMc found here: http://www.network54.com/Forum/74182...butor+Gear+Pin

Mallory distributors for Ford engines have been famous for shearing roll pins for 30 years. I tried to get them to do something about it for the entire eleven years I worked there.

To be fair, the problem started decades ago for the best of intentions. The story goes like this:

Unlike all other domestic makes, stock Ford distributors have gears which are pressed onto the shaft AND pinned with a .125" roll pin. The press fit takes 3/4 of the torque. All other makes of stock distributors have a slip-on gear. Most slip-on gears (including Chebby) use a larger .187" roll pin. The only slip on gears that use the smaller .125" pin are Olds and Mopar. However, unlike Ford, Olds and Mopar gears DO NOT TRANSMIT THE TORQUE REQUIRED TO TURN THE OIL PUMP. Mopar distributors don't even have a gear on the distributor and Olds gears have a hex in the bottom of the gear so the torque required to turn the oil pump is not taken by the roll pin.

In the 1960's when Mallory got into the performance aftermarket in a big way, they originally pressed the Ford gears onto the shaft just like OEM. But besides being a pain in the butt to do on the distributor assembly line, it also makes it very difficult for the customer to change a gear in the field (if the gear is damaged or if the steel gear needs to be replaced with a bronze gear for a roller cam). So, to appease customer complaints and to make the distributors easier to assemble, Mallory quit pressing the Ford distributor gears on the shafts sometime in the 1970's. The problems started soon after that.

About one in four Mallory distributors for Ford engines will suffer a roll pin failure at some point. Thick oil, high volume oil pumps and garbage in the oil pump all make a failure more likely. I ran a Mallory Unilite with the .125 pin for several years in a 289 '65 Fastback and never had a problem. But I ran standard weight oil, stock oil pump and I was lucky.

To be fair to Mallory, some of the newest Mallory competition series distributors for Ford use the larger .187 pin. But most of the common Mallory Ford distributors continue to use a slip-on gear with a .125 pin. Mallory does not really want to change the roll pin size because it would greatly complicate the replacement gear situation for the service department. Plus, the OEM gears would no longer interchange.

To fix the problem, simply drill the holes in the gear and shaft to .187 (3/16) and use a 3/16" roll pin. If you are worried about the shaft being too weak, use a .156 drill and roll pin. But do not rely on the .125 diameter roll pin. Install the larger pin BEFORE the smaller one fails.