Ford Model-A Notebook|
Is there such a thing in Model A Fords? There sure is and it is peculiar to 1931 Model A & AA vehicles. The indented firewall was phased into factory production starting in April 1931 and reached 100% production use in May 1931 according to a factory service bulletin. However, the indented firewall was only one part of a much larger design change that encompassed replacing the gasoline tank in all Model A & AA production. If you have the Ford Service Bulletin for May 1931, page 560, refer to it while you read this article.|
The bulletin starts out with, "A new design cowl tank A-9002-E is now being used in all Model 'A' cars and 'AA' trucks. The new tank replaces the previous design A-9002-C tank which will be obsolete after present stocks are exhausted."
Ford's bulletins use some "horse & buggy" era terms that need translation into Model A hobby jargon we can understand. So here are some definitions:
Figure 1 - Straight Firewall, 1930 - April 1931
Figure 1 shows the traditional flat firewall typical of Model A & AA vehicles produced throughout 1930 and until about April 1931. Now compare the flat firewall in Figure 1 to the indented firewall in Figure 2. There are several differences apparent: the indent; the stiffening ribs; the patent data plate location; the new gasoline shutoff valve. This discussion is not about the engine clearance recess in the center of the firewall, common to all Model A & AA vehicles.
Figure 2 - Indented Firewall, April 1931 & Subsequent
Figure 3 shows the "as built by the factory" arrangements of the old A-9002-C and new A-9002-E cowl tanks. Observe these differences:
New Gasoline Tank Arrangement
Figure 3 - Factory Built Gasoline Tank Arrangements
Suppose a dealer was confronted by a customer owning a Victoria with a straight firewall. Suppose this Victoria suffered front end damage in a collision and as a result, the cowl tank was leaking at the steering column support. The dealer likely would have retrofit the new A-9002-E tank into the damaged Victoria as shown in Figure 4. Figure 4 is like Figure 1162 of the May 1931 Service Bulletin.
Factory Built Installation of New Cowl Tank
Figure 4 - Dealer Retrofit Cowl Tank Installation
The retrofit installation makes use of the old carburetor by mounting the new side filter bowl directly into the gas inlet port. Compare the carburetors in Figure 4 and note the difference in filter bowl locations. Although mounting the new filter bowl in the inlet port of the existing carburetor dictated the special retrofit gas line A-9240-C, the special line saved the customer the cost of replacing the more expensive carburetor.
Also note the special retrofit A-9074-R adapter. As far as potential gasoline leakage is concerned, the adapter was a step backward, but it too reduced the customers cost. The alternatives Ford avoided would have been considerably more expensive to the customer, (a) producing a cowl tank with a special fitting to reach the straight firewall or (b), retrofitting the indented firewall.
There are 2 different styles of indented firewall. At the time the new cowl tank installation started going into production, Ford had a stockpile of straight firewalls. These were re-stamped to add the indentation. As a result, some of the stiffening ribs, shown dark in Figure 5, were flattened. The patent data plate was relocated, but the 4 patent plate attachment holes in the old location were left open.
Figure 5 - Re-Stamped Firewall
Indented firewalls, including re-stamped ones, are found in both straight and slant windshield Model A's, and in Model AA's. It appears no effort was made by the factory to direct re-stamped firewalls to commercial vehicles. The presence of an indented firewall is a piece of significant evidence that helps narrow in on the body assembly date of a 1931 Model A or AA.
Hopefully, this article clarifies the indented firewall which is often confused with the more common indentation for the engine found in all Model A & AA vehicles.
Updated 12:02pm Sunday, Jan. 24th, 1999
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