Distributor rebuild

[toytron]

Hello group,

I was wondering what it would take to remove the bearing from the distributor housing and installing two bearings for the added benefit of closer side play tolerances.

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[Scott V]

if your talking about bearings............thats going to be a really hard job. if your not a good machinist - not a job for you to do.

if your talking about bushings............its not too bad but to do it right youll need to line hone the bushings to fit the dizzy shaft.

you can also buy housing w/2 bushings installed. http://www.corvair.com/user-cgi/search.cgi?part=C5388

-Scott V.

[66vairguy]

On the other forum someone had a distributor shaft seize up in the housing above the oil pump. The distributor had the two bushing modification. It was thought the extra bushing caused the distributor shaft to bind in the oil pump housing - possibly from side loading.

While the extra bushing seems like a good idea it really isn't needed in my opinion. The DELCO distributors of the 60's were durable and well regarded, compared to distributors from other manufacturers. Typically a single bushing DELCO distributor can go 50,000 miles or more without issue, IF the engine oil is changed on schedule. Most of us will never put over 50,000 miles on a rebuilt distributor.

Bottom line - it's easier and adequate to replace the one bushing. Also check the other moving parts in the distributor as they can wear.

[toytron]

Thanks for your inputs Scott V and 66vairguy.

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[wbabst]

I took my distributor apart and rebuilt it.

I drive my cars everyday and while the single bushing is very adequate the second bushing helps keep the shaft aligned. I don't know about the seizing up, that would have to be the result of the bushings not being reamed to size after installation to ensure alignment and proper fit on the shaft. If you want to do it you will need access to a lathe, the bushing in the bottom of the housing will not fit until you turn the opening is machined to the OD of the bushing.


Clark's provides the service and sells distributors with the two bushings already installed for you.

[Steve62]

I may be wrong, but it seems to me that the shaft is held in alignment by the bore in the rear cover, where it enters to drive the oil pump. Is the second bushing really necessary in the distributor housing? Would it prevent, or at least hinder, oil from reaching the upper bushing?

[66vairguy]

I may be wrong, but it seems to me that the shaft is held in alignment by the bore in the rear cover, where it enters to drive the oil pump. Is the second bushing really necessary in the distributor housing? Would it prevent, or at least hinder, oil from reaching the upper bushing?

I agree that shaft play is not an issue as the lower hole in the oil pump housing that the shaft fits in is rarely worn. Replacing the top bushing takes care of the shaft wobble issue at the points cam. This is why adding a second bushing doesn't seem necessary and of course if the lower hole, and two upper bushings don't align you are going to have a failure - as was suspected in the seized distributor shaft in the oil housing I mentioned earlier.

So a little play in the distributor shaft before installation is actually a good thing to allow for tolerances of the machined oil pump housing. Once installed the shaft play at the points plate should be within spec. with a single new bushing, assuming the points cam is good.

[toytron]

I was reading some info from some fly corvair people and they kinda came to the same conclusion about the second bearing not being necessary. They said that they worked well for 50 years and that replacing them and making sure the shaft is good is probably one of the best things you could do. For heavy duty use a second bearing might be good but it must be align bored/reamed. I just disassembled and cleaned one and the difference just cleaning it up made is amazing. The shaft and bearing seemed in good condition. I need to replace one of the mechanical advance springs but I'm going to replace them as a pair. I did notice that the weights could be put in two different ways so we need to make sure that we don't reverse them.

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[wbabst]

I am not trying to convince anyone that they have to convert their distributor to dual bushings. I chose to do so because my upper bushing was very loose and figured if I am going to overhaul the distributor why not do it. If you do not line bore your bushings they will more than likely bind. A bushings ID tends to get smaller as a function of being pressed into the bore. That is why you often ream to size after installation. With two bushings you have to ream or line bore them to that they are on the same axis. The bottom bushing fits in the housing with openings all around it allowing oil fumes to get past it to lubricate the upper bushing with out any issues. It is all a matter of trying to keep that shaft as stable as possible. The more stable the shaft the better your points will work if you still have them. That said, I have driven many cars, many hundreds of thousands of miles with an original distributor with a single bushing and everything was fine.

[toytron]

Oh no Wbabst. I think the dual bushing is a great idea. I will probably use it for one of my other cars. I plan on building one that I might go all out on and I will probably do the dual bushing in it. I was just looking for ideas and I think the dual bush is a great one. I don't see any real problems with it if it is done correctly. I also want to thank everyone for their input and the pictures of the dual bushed unit. I didn't know if it was done on both ends or that the original was just lengthened by adding a second one.

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