Are distributer shaft failures common to the 335 series engines at all? Any major oiling issues down there with these blocks?

Background:
My 79 F-250's engine gave out on the freeway last night, actually ignited the brush on the roadside and started a good size fire that almost engulfed my truck which was stuck.

Engine had two brief hesitations and seemed to start losing a little power, this is at 75mph with a 4 speed, no tach so don't know the exact RPM. Then it popped and crackled real loud for a few seconds and shut down. As I coasted I saw multiple small fires to my rear on the exhaust side.

After fire was put out me and a few of the volunteer firemen who were mechanics started going over the truck/engine. No visible problems, engine turned over, fuel getting to the carb, coil firing. Took off the distributer cap and the rotor turned free - major problem!

So, it looks like there was a failure somewhere in the distributer shaft, possibly the shearing of the drive gear. When that happened the timing immediately went way out of whack and raw fuel made it into the exhaust, ignited and blew out the tail pipe igniting the fires. Engine shut down fast due to no timing at all.

I am going to pull the distributer tonight and see what I can find. Has anyone had this happen at all? Wondering if the engine will be ok otherwise, and if the shaft sheared would bottom pieces remain in a bore with a bottom or would they fall free into the oil pan?

 

There is a roll pin that goes thru the distributor gear, and the distributor shaft. It has sheared, pull the dizzy, get a new roll pin, feed it thru the hole, trim it, and put it back in on number 1. Thattl take care of it. Make sure you put the gear back on the dizzy shaft the same way it is when you pull it out. I dont know if it is common, but this has happened to me 2 times, all one on floyd hill, one in my town, west of denver. I think the roll pin is 12 cents at any car parts store.


---JOHN

 

Thanks! Glad to hear it will probably be something minor. Mine happened just outside of Ft. Morgan, $250 tow to Denver.

I've never re-stabbed a distributer before. Do I turn the eninge until the timing marks are at 0 degrees, then put it in with the rotor on #1?

Is the sheared pin most likely in the oil pan where it is safe from blocking any passages?

 

That's right but you have to make sure your at top dead center.Number 1 piston should be at the top of it's stroke with the timing marks at tdc. Then you have to allow for the fact that the gear will cause where your rotor points to turn in relation to where you started at as the gear engages. Then make sure the star fin in on the shaft is precisely lined up with the pickup. Fire it up, oops, sorry, and set the timing with a light.

 

The oil pump may have seized up to make that pin shear.

 

Any way to check on that easily? Would it develop enough pressure to trigger a reading on the stock guage just cranking it with the starter?

 

The distributor drives the oil pump. While you have the distributor out, put a tight fitting 5/16 socket on your 1/4' drive extension, you should be able to turn the oil pump if its free, ccw rotation.

 

Ive always just used compression to drop the dizzy back in. Get a helper, pull the dizzy, get it ready to go in. Pull the number one plug, that is the one on the front, on your left side as you are facing the front of the truck to work on it. Have your helper, or you bump the key untill there is pressure coming out of the #1 plug hole, your then on number one. Then just rotate the rotor to the number one position inside the dizzy, and drop it in. Then set the timing with a light. Its a little more inepth than this, but it is real easy. Hasnt failed me yet. And also, if you stomp on the gas alot from a dead stop, or roast your tires, it can put sudden torque on the roll pin, and shear it. But deffinently check the oil pump as mentioned by other users here.


---JOHN