Worn Distributor gear pad

[PaulProe]

helping someone with their FE in a replica, ran into a ignition problem. Seems the gear support pad for the distributor gear is worn enough the gear is lowered about  .050" and is wearing very prematurely. Cast Iron on cast iron, less than 200 miles and it already is 25% gone.

Any suggestions on how to fix something like this. The picture shows the wear on the bearing pad. Engine builder probably should have caught this but now, it's water over the dam.

Click on the attachment and you'll see the wear pattern.

Thanks

Paul

[C6AE]

In this case, where the block is already bushed I would probably make up a bronze thrust bushing or remove the existing bushing and press one onto the distributor shaft.

[wayne]

Just  make a .050 washer that fits on the dist gear lock tight jt on so it dont fall off when it goes back in.

[Nightmist66]

What kind of distributor? Unless the pad was already like that, I would say the distributor/gear was set up incorrectly. Should not see any kind of wear like that....

[KMcCullah]

Bummer! I'd be pulling this one apart. The bore appears to be bushed. Did the oil hole get drilled after the bushing was installed?

[C6AE]

Just thinking out loud now but is the oil pressure hole to that bushing open and working?
I wouldn't think the gear would care if if was lowered by .050, the mesh should still be well onto the face of the dist. gear.

[wayne]

Is it a 391 truck block they need a bushing to use a car dist

[PaulProe]

It's originally a 360 block, now bored & stroked. Current distributor is an MSD but we believe the damage was done prior to all of this. Suspect the block was probably bad in the beginning and the machine shop missed this - kind of hard to reconstruct. Everyone wants to blame the other guy.

As far as gear mesh, helical gears don't like mismatch, and .050" on this small a diameter gear is really a big deal. Imagine the ring and pinion being mismatched by the same amount. It would howl like a banshee.

The hole is not bushed, that is just the way it appears in the photo. Everyone would like to be able to fix it 'in place', but to do it properly, it probably is going to involve pulling and tearing down the motor.

Open to any othe ideas, thanks for those that have been offered.

[67xr7cat]

If the gear is located correctly it does not ride against that pad. Ford and MSD have instructions on how to properly locate the gear on the distributor shaft.  Is a common problem problem where the gear is in the wrong place. Do make sure the oil hole in the pilot hole is there as that is how oil gets to the distributor gear for lube.

[67xr7cat]

Look at reply #13 in this old thread

http://fepower.net/simplemachinesforum/index.php?topic=958.0

It explains how to properly set up your distributor. Get your distributor right and don't worry about the wear on that pad as it does not matter. Is only there because at some point someone had a distributor in there with the gear in the wrong spot.

[C6AE]

Ring and pinion gears are hypoid.
Helical gears only need to be parallel or at 90°. The exact height of the distributor gear should not matter.

edit to add; If I remember correctly, the thrust force on the distributor gear is downward toward the block pad, so in that regard it may matter that it will need contact, but the exact position is non-critical.

[KMcCullah]

Look at reply #13 in this old thread

http://fepower.net/simplemachinesforum/index.php?topic=958.0

It explains how to properly set up your distributor. Get your distributor right and don't worry about the wear on that pad as it does not matter. Is only there because at some point someone had a distributor in there with the gear in the wrong spot.

Hey I remember that old thread. I remember it because the FoMoCo spec for distributor gear location (3.071-3.078) differs from the MSD spec (3.045-3.050). I'm guessing the difference is due to the MSD being a ball bearing unit with no end play. Just something to be mindful of.

[blykins]

Look at reply #13 in this old thread

http://fepower.net/simplemachinesforum/index.php?topic=958.0

It explains how to properly set up your distributor. Get your distributor right and don't worry about the wear on that pad as it does not matter. Is only there because at some point someone had a distributor in there with the gear in the wrong spot.

Hey I remember that old thread. I remember it because the FoMoCo spec for distributor gear location (3.071-3.078) differs from the MSD spec (3.045-3.050). I'm guessing the difference is due to the MSD being a ball bearing unit with no end play. Just something to be mindful of.

The specs are different because the shaft is pushed in on the msd spec and pulled out on the ford spec.

[67xr7cat]

Ring and pinion gears are hypoid.
Helical gears only need to be parallel or at 90°. The exact height of the distributor gear should not matter.

edit to add; If I remember correctly, the thrust force on the distributor gear is downward toward the block pad, so in that regard it may matter that it will need contact, but the exact position is non-critical.

 If you are high or low you will have less tooth engagement. I can say from past experience with bronze distributor gears they wear a lot faster when you don't follow Fords instructions. As for thrust pull the shaft out of the distributor and you will find a bushing designed to take the thrust you are talking about. Ford did all the engineering. Steve

[C6AE]

 If you are high or low you will have less tooth engagement. I can say from past experience with bronze distributor gears they wear a lot faster when you don't follow Fords instructions. As for thrust pull the shaft out of the distributor and you will find a bushing designed to take the thrust you are talking about. Ford did all the engineering. Steve

I'm going to suggest that the (non lubricated) oilite thrust bushing in the distributor is not designed to take the thrust load of the distributor gear. (A look at the bottom of the distributor gear, will show an obvious heavy duty thrust surface with pressure lubrication)
   When I assemble an FE, I confirm that the lower distributor shaft actually lifts off of the inner distributor thrust bushing a couple of thousandths. If it doesn't, the thrust bushing inside the distributor will overheat and fail. I have seen this failure on more than one of the old YL Mallory type distributors which were not built to as accurate a tolerance as the oem Ford stuff.
The actual location of the intersection along the axes of the cam and distributor gear allow for significant tolerance variation of each.

[67xr7cat]

 If you are high or low you will have less tooth engagement. I can say from past experience with bronze distributor gears they wear a lot faster when you don't follow Fords instructions. As for thrust pull the shaft out of the distributor and you will find a bushing designed to take the thrust you are talking about. Ford did all the engineering. Steve

Sounds good. Do what works for you and I will do what works for me which is setting the gear height based on what Ford specs.

I'm going to suggest that the (non lubricated) oilite thrust bushing in the distributor is not designed to take the thrust load of the distributor gear. (A look at the bottom of the distributor gear, will show an obvious heavy duty thrust surface with pressure lubrication)
   When I assemble an FE, I confirm that the lower distributor shaft actually lifts off of the inner distributor thrust bushing a couple of thousandths. If it doesn't, the thrust bushing inside the distributor will overheat and fail. I have seen this failure on more than one of the old YL Mallory type distributors which were not built to as accurate a tolerance as the oem Ford stuff.
The actual location of the intersection along the axes of the cam and distributor gear allow for significant tolerance variation of each.

[Faron]

In a perfect situation the gear DOES ride on the Pad, with about .010-.015 end play ( pushing up from the bottom )  , its not designed to be constantly pulled down , if it is,  it will wear out the top of the Dist bushing , i would set up a dummy dist with the gear at 3.050 at maximum depth ,( i prefer the MSD spec I've verified it with a block and its the easiest way to measure )  I would measure the distance to the worn area of the block and make something to replace the worn area , some type of spot face tool would make a flat surface then perhaps a flange style  brass bushing inserted in the hole , this would of course require a complete disassembly of the block , but a good machine shop should have no problem doing it

[C6AE]

It is often overlooked how much work that gear does driving the oil pump. A high volume pump with a cold engine can tax the assembly. The thrust force must be great and torsion will occasionally shear the pin through the drive gear, or; twist up the driveshaft... I run the larger pump but keep this close to mind when the engine is cold.
To check the end play, I disassemble the advance mechanism and insert the lower part of the distributor in the block and measure with an indicator, comparing (subtracting) the number from the actual endplay in the distributor itself.

(Another fix, which I hinted at earlier is to remove the existing bushing from the block and press a steel sleeve with a shoulder under the gear on a passenger car distributor.. I have done this and it works perfectly with a drop of locktite for insurance. You are left with a steel shaft running in a cast iron bore, which is what Ford intended from the start.)