1930-31 Model A

Ford Garage

Eaton Gas Cap Detail Differences

Pictured here are a pair of original 1930-31 style Eaton gas caps. These are the style with the removable inner cap with the pressed-on stainless shell. They are shown separated from the shells for restoration of the stainless. The inner caps were previously re-plated with cadmium.

What makes these gas caps interesting is that the cap on the left is vented, and the one on the right is not.

The un-vented cap on the right was removed from a Model A which would not run properly and would vapor lock. The cap on the left has the typical venting found on this style cap.

Pictured above is an (upper) inside view of the caps, showing the difference in the stampings for the venting.

The cap on the left clearly shows the two vent holes on the outer perimeter, as well as the two lanced diamond shaped holes in the inner section. This is the typical vented Eaton cap construction.

The cap on the right has no vent holes on the outer perimeter, and also does not have the two lanced diamond shaped holes in the inner section. There is no way for the fuel tank to vent past the cap gasket!

The pic above is the bottom view, as seen when the cap is removed from the tank. The vented cap on the left shows the detail of the two vent paths, and non-vented cap on the right clearly has none.

The close-up also shows the similar-but-different Eaton names and logos stamped in the steel tangs of the two gas caps.

So the question remains:
What is the reason and usage for the un-vented Model A Ford gas cap? It is an original, not a reproduction.

July 2010