My parts books list the cap 1838100 as fitting 29-32 and all using the same distributor number. I have 4 caps that are black and two spare bodies and all interchange correctly. My guess is that the cap you received is not a 1838100 . Also all my distributors are 633 J . I don't have a 4 cyl parts book but saw a listing for a 533G  distributor on Ebay for an 24-25 Chev. 

The Super Chevrolet Service 1929-1934 Parts Manual for Automobiles and Trucks.

Key item is that the effective date is 1934.

It would be nice to find an earlier parts book prior to 1934 to see the distributor and cap part numbers listed in it.

More homework!

my parts book is Feb.32  Chev cap part number 822465 for 29-30-31-32  dist. # 828317 for 29-31 and 1843839 for 32. No Delco numbers are listed. The 1838100 listed above is the Delco number for the 822465.  My 29-42 parts book list the cap part number as 1838100. Please read the above post and advise if your dist. is a 533G. Not sure when Delco became a part of GM. Looks like 1918 according to Google so the next question would be when did Chevrolet switch to using Delco part numbers vs. Chevrolet part numbers in their parts manuals.

I tried to reread the distributor model number and I feel that it is a 633G and not a 533G The date plate is not clear. 

Also,

Kettering founded the Delco (Dayton Engineering Laboratory Company) in Dayton, Ohio around 1916.

He sold Delco to General Motors in 1918 and became head of General Motors Research.

I ordered a 1929-1932 Chevy parts manual from Faxon today as a reference tool 

@paul-baresel I would contact the vendor you got the cap from and let them know the issue. Also I checked the Faxon site and it appears the 32 manual they list is a reprint of the January Price list. It would be best if you can find a later one if you are using it for a 32 as the January print version will have very little info on the 32. Even the Feb. copy I have is not complete as Chev. was in the middle of the production year. I think the later 32 print was August of 32.

I agree with you and tried to find an early parts manual for 1929 itself, or within a couple of year ahead of 1929. My goal was to see if there was any information to help me to see what the parts numbers were back then.

I did talk with the person who I bought the parts from and sent him photos, etc. That person has always dealt with the new black caps. That person was not familiar with the "brown cap". 

What is bothering me is that I know that this issue was probably brought up before me, but I am not a good computer user, so I really appreciate everyone's input to try to resolve this conundrum. There must be a reason for the change in caps, but I am running out of ideas where to look. So, any suggestions are appreciated.

@paul-baresel 

Hi Paul

This may or my not be relevant here, but...

I bought an NOS GM Delco distributor cap (in the original box) for my '46 with it's original engine and distributor.

The cap SHOULD have fit everything from about 1934 up to the last of the 216's in 1953.

When I got the cap, it wouldn't quite fit down on the distributor and was cocked up a little on one side.

And that meant the retainer would snap in on one side, but not on the other.

I thought I had a fluke cap, so I bought 2 more NOS caps from another source.

Same problem.

After a little careful work with a small file around the smaller diameter of the stepped edge around the lower edge of the caps, they do fit.

But I still think it's pretty strange that several genuine GM caps didn't quite fit without some work.

And I've never experienced this before.

@paul-baresel Did you try the used cap from the 1930 distributor? It has to be either the cap or the distributor body that is different. If you have a digital caliper you could measure the the height of both caps at the clip seating area . Also be sure the cap is seating fully in the recess . It could be the locating tab in the cap is slightly oversize and not allowing the cap to seat.

I have found the same problem with some caps (they don't fit down on the housing until a little excess Bakelite has been filed off. The original caps on 1931-32 were what I call oxblood or a reddish brown. The original Delco-Remy caps are very hard to find. Some after markets are easier to find. The black caps are later production.

Relying on part numbers can be unreliable. Part numbers are not changed even though the parts are not identical. Then there are instances where the part numbers are changed without any noticeable changes in the part.

It is nice to know that I am in good company with this dilemma. I have to call this Monday and talk to The Filling Station. The company was closed for the holidays. I also contacted Gary Wallace earlier and he has not come across this issue. The caps Gary orders are black. I did send the photos of the brown/oxblood caps to Gary as well.

The Filling Station only sells the black cap as well.

I never thought of filing down the Bakelite until Chip and Stovebit talked about filing down the caps a little to make them fit. I have the black cap from Gary that I can experiment on to make it fit.

I agree with Chip about part numbers. I was trying to find an earlier parts book and really did not come up with what I wanted on eBay so I bought from Faxon. It is still a good reference tool.

I will let you know how I make out filing the black cap down.

Yes, I also bought two extra caps that are black. The caps did not fit.

I plan to call Gary and tell him what I have learned about the caps. 

Thanks for everyone’s input to this discussion 

Paul

I solved the distributor cap dilemma. I bought a copy of the Chevrolet Master price list from Faxon books. It covers the years 1929-1932. The book is the earliest years I could find for part numbers.

Page 108 shows the breakdown of the distributor and the oxblood cap that is used on my car. The significant identification marks are the small to large circles in the cap.

Page 107 identifies the part numbers for the distributor body.

The cap number is 822465.

There are two distributor part number.

     828317

     1843839

The letters in the very first column is known as “Telegraphic Code” for ordering part

I am thinking that my distributor body has the wrong tag on it, or someone was using spare parts to make my distributor labeled as a 633-G??

@paul-baresel The photo is the same as my Feb 32 parts book. The letters in the first column are actually the year identification-I=1929 international  U=1930 Universal  Ind=Independent 1931 and C=1932 Confederate.