Broken Distributor Gear
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Senior User
Joined: Jun 2003
Posts: 417
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From: Napanee, Ontario, Canada
Broken Distributor Gear
I have a 390 that wouldn't start (74 F100). I thought I was having a spark problem only to find out tonight that my rotor was not turning at all. I pulled out the distributor and found 4 teeth sheared off the bottom gear. The truck is not a daily driver, maybe only 3000 miles a year. The motor has been rebuilt (not by me so I don;t have cam, oil pump etc detail). It was rebuilt about 3-5000 miles ago. The truck did have a rough idle before this happened and was unpredictable (would stall out, poor response etc). The bottom gear is brass. The distributor does look like the original and the cam that the points run on does look rather worn.
Based on this I have a couple of questions (concerns)
1) How did this happen? Is this the distributor or something with the cam?
2) Do I need to drop the pan to get the brass pieces out or is oil change enough
3) Can you buy the gear seperate or should I spring for a new distributor.
4) Suggestions on aftermarket distributors
Current set up is stock points. I do have another stock system in a wreck out back but didn't want to install it and possibly ruin it without some advice first.
Based on this I have a couple of questions (concerns)
1) How did this happen? Is this the distributor or something with the cam?
2) Do I need to drop the pan to get the brass pieces out or is oil change enough
3) Can you buy the gear seperate or should I spring for a new distributor.
4) Suggestions on aftermarket distributors
Current set up is stock points. I do have another stock system in a wreck out back but didn't want to install it and possibly ruin it without some advice first.
Elder User
Joined: Apr 2004
Posts: 545
Likes: 1
From: Shreveport, La.
1- How it happened- Who knows, could be as simple as rough handling when being rebuilt.
Is sheer pin still intact?
Would also be worthwhile (even though it seems like a lot of trouble) pulling timing cover off and checking timing gears/chain for any damage and/or unusual wear.
If you can get dist out of the way, and get in position to look down shaft hole, suggest checking out cam gears one by one, if they are jagged looking or really rough looking, you might as well plan on going back in far enough to replace that also, or have it done.
2- To be absolutely safe, yes. Although chances are good those pieces won't cause any trouble. But they may under right circumstances 'float' up and get caught/washed into driveshaft movement.
3- Gear and sheer pin are available seperately.
4- If all else is stock, and np plans to switch over to electronic ignition, suggest going back with stock.
?? With distributor out, can engine still be turned over by hand?
Is sheer pin still intact?
Would also be worthwhile (even though it seems like a lot of trouble) pulling timing cover off and checking timing gears/chain for any damage and/or unusual wear.
If you can get dist out of the way, and get in position to look down shaft hole, suggest checking out cam gears one by one, if they are jagged looking or really rough looking, you might as well plan on going back in far enough to replace that also, or have it done.
2- To be absolutely safe, yes. Although chances are good those pieces won't cause any trouble. But they may under right circumstances 'float' up and get caught/washed into driveshaft movement.
3- Gear and sheer pin are available seperately.
4- If all else is stock, and np plans to switch over to electronic ignition, suggest going back with stock.
?? With distributor out, can engine still be turned over by hand?
Senior User
Joined: May 2004
Posts: 367
Likes: 0
it could be a couple of things, as mentioned. it could of been age, installed wrong, bad cam gear. be sure to check the camshaft gear for wear. you can by new gears at the parts store. nothing wrong with points, but i preffer electronic ignition over points. i have a mallory dist with pertronix module if interested?
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