I was driving along today on the highway when the engine spontaneously quit and wouldn't restart. I determined that the rotor was not turning under the distributor cap and that the cam gear teeth must have sheared.

I intend to replace them with all metal gears. Does anyone have the part number to a set of metal gears that would work on my truck? How much more work would it be to put a new cam in it? I've done cam swaps on V8s but am not too familiar with the inline 6.

For now, the engine is all stock. Eventually, I will rebuild it entirely, maybe increase the compression a little bit, swap on a 4 barrel and EFI manifolds. I just figure if I can pick up some power now with a cam swap, this would be the time to do it, unless it's a ton of extra work. I also read that the cam gear can be stuck on the cam pretty good and thought it might be worth it to put a new mild cam in it.

 

Before you tear down the front of the engine, pull the valve cover and make sure the cam isn't turning. I've seen a couple that sheared the roll pin on the distributor gear.

If it is the cam gear that's toast you really need to drop the oil pan and pull the pick up tube. You need to thoroughly clean them both out. If you don't all that crap usually ends up plugging up the screen on the pick up tube and causes more damage.

I personally prefer to pull the engine and throw it on a stand. That way it's easier to do the work. I hate pulling the oil pans off of a 300 in a 80+ truck with it still in the truck.

The cam gear is pressed on, not bolted on. And I found the best/easiest way to deal with pulling the cam gear, is to pull the whole cam out. Then press the gear off with a shop press. When doing this you need to be careful not to break the cam retainer plate.

If you are considering a cam swap. This is the time to do it. Just make sure to transfer all the hardware over from the old cam.

If you do pull the engine to do this. It's also a good time to pick up a complete gasket/seal set and replace them all.

 

Man, I'm glad I made this thread before ripping into it! I pulled the distributor out since I figured if it was the culprit, it would certainly have to come out, and even if it was the cam gear, it would have to come out anyway. Well, the distributor - which is a new HEI piece only a couple months old - came out in pieces. The roll pin holding the gear to the shaft had sheared, just like you said!

I am still scared of the phenolic timing gears shearing. This engine has been abused and is tired, but at least I can keep driving it until something more serious breaks! Thanks for the sound advice!

 

Glad to hear you found the problem. When I have an issue like that, I like to start by checking the simplest/cheapest items to fix and work my way up to the "Oh crap" items.

It sucks that you had the issue on such a new item. But it's not totally unexpected on a lot of the new parts. Imported hardware isn't the best quality. So sometimes things fail. It sucks but it's getting to be the new normal.

I wouldn't worry too much about the timing gears until they fail or you tear into the engine for some other work. Then install a good set of metal gears.

 

Here is what I have done to prevent the roll pin from shearing, which is especially a problem with my race cars since I use a magneto that takes a lot of force to spin, putting a high load on that pin:

Remove the broken pin.
Ream out the gear and shaft pin hole with a 1/8" reamer.
Use a piece of 1/8 welding rod - which has high strength and good ductility, and just as important, is solid, not hollow - in place of the roll pin. I first melt a globule on to the end of the rod with a TIG torch, cut the rod so it will just stick out the gear hub when inserted into the gear hub, then melt a locking globule onto the other end of the rod to lock it permanently to the gear and shaft. Be sure the globules do not stick out too far to interfere with the gears meshing. Grind them down a little if needed.

P.S. The engine is free-wheeling, meaning if the gears shear no valves will hit the pistons so damage is generally contained to replacing the gears.

 

That's great! Thank you all for the help. I got her running again today. This new, new distributor is much better anyway. It has more total timing with the same 12* base and it feels snappier at low RPMs. I never messed with the timing curve on the old new distributor, but I'm glad I didn't because of how it fell apart. I'll still fix it and keep it as a backup. Oh, and my vacuum advance actually works with this new one, too.