Oil return pipes and tappet covers.
 

In the original late Model 'A' parts price list it shows only one tappet cover and it's associated oil return pipe. Pipe A-6645. Cover A-6520. There were two pipes and two matching covers, as we all know. I presume first generation is shown, as there is no 'B' prefix after the part number as other parts. The book states 1928-31 for these parts shown.
My question is, why is the other pipe and its associated cover not mentioned and listed with a 'B' prefix? I would have expected the later two parts to have a 'B' suffix ie; A-6520-B and A-6645-B as other parts in the same book, for instance the Flywheel assembly A-6375-B 1928-31.
If the later parts are shown only, as the Flywheel housing, why show earlier parts?
Your thoughts. (Or am I barking up the wrong tree?)

Re: Oil return pipes and tappet covers.
 

They stopped selling/supplying the early version so they dropped it from thier catalog.

Re: Oil return pipes and tappet covers.
 

Looks like you'll have to replace the pipe and the cover as a pair. If I were doing that, I'd replace the cover with one with an oil filter unless you are wanting to show the car..

Re: Oil return pipes and tappet covers.
 

I think it was pretty normal for parts to be evolved without iterating the part number. You see it in the service bulletins all the time, e.g., "The gas valve handle A-9191 has been changed from a forging to a stamping and the length of the shoulder on the gas valve reduced..." Both the old and new designs were filed as A-9191. Another classic example is the throttle control assembly. All variations of the assembly are A-9725.

I think they distinguished between part changes where the old and new parts are interchangeable except for some small detail (same part number) and those where the new part either doesn't fit the same as the old part or where the old part is deficient in some way where they want to expedite removal of that part from the supply chain.

Re: Oil return pipes and tappet covers.
 

Fords part numbering policy for the model A didn't always include "AR" suffixes for replacement parts. Key parts, such as the difference between Able and Bendix starter drives had to have suffix differences since the early starter was inclusive to the early type multi-plate clutch and transmission set up but they didn't offer the parts for a very long period of time. At some point things like the early service brakes and transmission combinations would have had to be changed to the late configuration for service part availability.

Re: Oil return pipes and tappet covers.
 

The "AR" designation is the least understood and most miss used in my opinion. The slide shows Ford's part numbering system.

Re: Oil return pipes and tappet covers.
 

Except that what we've been discussing in this thread is that Ford clearly did make substantial changes to parts without adding a suffix to the part number.

Re: Oil return pipes and tappet covers.
 

There is a a-6645-r part available to replace a damaged return pipe when using the the old cover. the cover does not have have a -r part. Apparently ford wanted you to replace the broken cover and return pipe as a pair and the change wasn't great enough to warrant a change in part number.

Re: Oil return pipes and tappet covers.
 

It's interesting what part numbers were published in the "green bible" otherwise know as the Ford Chassis Parts and Accessories Catalogue dated November 1950. This included all available parts for Ford vehicles manufactured from 1928 through 1948. A lot of available parts for model A are the latest interchangeable part and many have a B prefix instead of the A prefix. A lot of these parts were used up through 1948 but still carried the old prefix.

Ford's part numbering system made sense to them for the most part so they weren't concerned about what the public at large thought about it. Folks went to their Ford dealer to get manufacture specific parts. Things have changed a lot over the years in this respect and it's mostly due to the restoration and maintenance of these old vehicles. Long after Ford quit producing obsolete car parts, there are still some NOS parts to be found out there so folks still need to know what they are looking for.

Re: Oil return pipes and tappet covers.
 

I suspect that changes made to Model A parts without a corresponding changes in part numbers involved mostly castings & forgings. These two kinds of parts are subject to the pattern makers & die makers individual craftsmanship. The nature of pattern making and die making in days of old caused variations as no two people worked alike. However, it was the finish machining of castings & forgings that made them interchangeable in fit and function.

Re: Oil return pipes and tappet covers.
 

You keep making this claim; it seems like you haven’t reviewed the ample evidence to the contrary, both in this thread and all over the service bulletins, that major design changes were made without changing the part number.