distributor main shaft

[Werner R.]

delco single point unit. i had a wobbly breaker plate, so, before i took i took the unit apart, i inspected it. i noticed that the upper bushing was snug against the shaft. however, the lower bushing was loose with about .005 side play. after i took it apart, i noticed MANY circumferential grooves where the shaft contacts the lower bushing. it loooks like the grooves of a record, and involves the entire contact surface of lower bushing and shaft. what gives here?? i thought the weak spot was the upper bushing. what kind of problem can cause the hundreds of circumferential grooves?? i am not aware of any lubrication problem. certanily the upper bushing was lubricated by the grease in the well and the contact surface is smooth. help, anyone??
werner

[Brian Monticello]

Re: distributor main shaft

While the upper bushing lacks constant fresh lubrication, the majority of the load is placed on the lower bearing. A substantial load results from driving the oil pump and it is lubricated by oil mist through holes near the bottom of the housing. Sounds like you had some dirt on the bushing or oil mist was not lubricating the lower bushing. Are those holes in the housing open?

Brian

[Werner R.]

Re: distributor main shaft

brian i didn't think to check the lower openings. i will follow up on this. thanks. werner

[Joe R.]

Re: distributor main shaft

Werner,

Probably sometime in the past the distributor has suffered the tach gears breaking. There is only one place for the chips to fall. They destroy the lower bearing. When the new shaft is put in to correct the tach problem, in time the lower bearing will destroy the new shaft. They both need changing at the same time along with cleaning out the housing of metal chips.

It's just a case of doing the correct repair at the right time.

Regards,

JR

[Clem Z.]

oiling the distributor main shaft lower bushing

on cast iron distributors i drill a small hole,.020/.025, from the oil gallery groove in the housing to the bottom bushing so to get pressurized oil to the bottom bushing as there is a lot of side force on that bushing. you can not do this to the aluminum housing distributor because the casting is hollow around the bushing. JR is also correct about the broken tach drive gear.

[Werner R.]

Re: oiling the distributor main shaft lower bushin

clem
basic question. i thought my housing was aluminum. i did not know there is a cast iron housing. is there any way to tell cast iron from aluminum ie magnet etc??
werner

[Clem Z.]

Re: oiling the distributor main shaft lower bushin

magnet is the best bet. i have never seen a corvette tach drive distributor that was aluminum. the HEI distributors were aluminum and that was what i was referring to.

[Werner R.]

Re: oiling the distributor main shaft lower bushin

thank you clem. one more question: i bought this used distributor from "some guy" on the west coast. there is a hole that leads through the housing to the plastic thrust button, for the tach gear. does this tell me the year of the distributor?? did the 63 to 67 units have a hole leading to the thrust button?? did they even use a thrust button?? someone said he threaded this hole and used a set screw to adjust tension on the thrust button.
the problem is i do not know what i bought from this guy. he said it was a rebuilt BB distributor for my car but he was a crook because he sold me a "rebuilt" unit, but it was just used and worn out. it had no felt washer or pastic washer; it has no cam lubricating wick; the cross shaft gear was badly worn; the drive gear is worn; the end play was about .090 inches; the breaker plate was wiggly, etc etc.
clem, always appreciate your insight.
werner

[Clem Z.]

before GM came out

with the plastic thrust button on the inside of the housing we drilled and tapped the end of the gear housing to install set screw with a outside lock nut to set the driven gear end play.

[Werner R.]

Re: before GM came out

thanks to one and all.
werner