Different distributor sizes?
 

I have a RS spec'ed motor and acquired an extra distributor )Bosch 231 184 001)and had it recurved/rebuilt as a spare. When I went to install it to dissassemble and clean the current dizzy I found that the refurbished one will not fit in to the case. When I calipered it I realized it is several MM larger diameter across the long portion of the dizzy case. I don't have the other dizzy handy to measure but I believe it is a 231 184 005. The new distributor measures about 3.05cm diameter for the "shaft" I have heard these can be machined down, if so who do you guys recommend for this. Also what cases is the larger distributor designed for..Is there a site that gives the dimensions of all Bosch dizzys? .. I may want to sell it.

Supertec offers a full service distributor service.
There are only two different shaft sizes. You have them both.
Early small shaft 2.0-2.2 63-71
The larger shaft fits 2.4-3.6 72<
There are of course many different distributors and some even rotor counter-clockwise.

Great Henry, I will be sending the dizzy out to your shop.
I am confused as to why my 2.7/2.8 would have the small shafted dizzy

Is your 2.7/2.8 built on an aluminum 2.0 case?
Is was a very common conversion built by amateur engine builders in the 80s.

the paperwork that came with the car when i bought it three years ago spec'ed a 7R case.I have not dropped the engine nor even looked at the #'s closely but will do so this weekend. It was built by Farmer in Indy about 6 years ago...seems kind of odd doesn't it

No 7R case came with a 27 mm distributor.
It is possible that someone installed a reducer sleeve.

The only reason I could imagine doing that is to use a special distributor. I.E.: twin plug?

I wish it was twin plug Henry!
I am going to get it back down to the garage this weekend and measure everything...now that I think about it this is really odd. I will get case number and measure the existing dizzy and all