Distributor wear
Tech Contributor
Joined: Aug 1999
Posts: 14,379
Likes: 6,390
From: At my Bar drinking and wrenching in Lafayette Colorado
I'm assuming you're looking for a tach-drive points-type distributor and not an HEI...
There are a few critical wear areas on the tach drive units:
First, the lower shaft bushing tends to get sloppy. When the lower bushing wears, it usually scores the mainshaft and trashes it. This requires a new mainshaft and a new set of bushings. Cost about $150. There should not be any significant lateral play in the shaft at the distributor gear.
The second critical area is the crossgear thrust surface. When the crossgear spins, it is pushed laterally into the side of the distrubutor housing. The area where it rides can get quite a bit of wear. When the wear goes too far, the crossgear will lock up in the housing, stripping itself out and shearing the gears off the mainshaft. This will require fabricating a custom thrust washer to save the housing, and it will require replacement of the crossgear, crossgear housing, and the mainshaft.
Over the years, different systems were used in the thrust surface area. Early distrubutors used the housing casting as the thrust surface. Later models used nylon thrust buttons. Aftermarket brass buttons are available, but have to be modified in order to fit.
You should assume that the vacuum advance control unit is trashed and will need to be replaced, and the mechanical advance system will be missing the stop bushing and will need to be fully rebuilt.
It would be tough to tell from photos whether or not a distributor is in good shape - you pretty much have to disassemble it and inspect it.
There are a few critical wear areas on the tach drive units:
First, the lower shaft bushing tends to get sloppy. When the lower bushing wears, it usually scores the mainshaft and trashes it. This requires a new mainshaft and a new set of bushings. Cost about $150. There should not be any significant lateral play in the shaft at the distributor gear.
The second critical area is the crossgear thrust surface. When the crossgear spins, it is pushed laterally into the side of the distrubutor housing. The area where it rides can get quite a bit of wear. When the wear goes too far, the crossgear will lock up in the housing, stripping itself out and shearing the gears off the mainshaft. This will require fabricating a custom thrust washer to save the housing, and it will require replacement of the crossgear, crossgear housing, and the mainshaft.
Over the years, different systems were used in the thrust surface area. Early distrubutors used the housing casting as the thrust surface. Later models used nylon thrust buttons. Aftermarket brass buttons are available, but have to be modified in order to fit.
You should assume that the vacuum advance control unit is trashed and will need to be replaced, and the mechanical advance system will be missing the stop bushing and will need to be fully rebuilt.
It would be tough to tell from photos whether or not a distributor is in good shape - you pretty much have to disassemble it and inspect it.
Le Mans Master
Joined: Nov 2004
Posts: 6,128
Likes: 21
From: North Alabama
Originally Posted by vettepilot68
If I were going to buy a used distributor 
, what would I be looking for 
? How do I check it to see if it is worn out or needing rebuild 
?
, what would I be looking for ? How do I check it to see if it is worn out or needing rebuild ?
