Gas cap finish

[Roger Coen]

I'm trying to find out the finish on the gas tank cap for my 67 BB. Its unfinished now but suffers from severe rusting everytime it gets wet. I can't believe that GM would deliver it that way. Any help? Anything I can do to keep it from rusting?

Thanks, Roger

[Joe L.]

Re: Gas cap finish

Roger----

The original fuel cap for your car, GM #3843576, was zinc plated. Many of these caps that I have seen appear to have been possibly galvanized rather than electroplated. No matter, though, in either case the finish is zinc; just a possible difference in the method of application. When new, these caps were relatively shiny. However, the zinc oxidizes rather quickly and the finish becomes more of a dull gray.

I don't know how your cap became bare metal subject to rust. It may be difficult to refinish in the same manner as original since the cap is an assembly of parts. Originally, the pieces were finished individually, then the assembly was rivetted together.

The current GM replacement cap, which is the original cap for 1968-69 models, is GM #3952708. This cap is very similar to your original cap. One difference is the fact that the original cap uses a thick fiber gasket whereas the 3952708 cap uses a neoprene rubber gasket. Functionally, the neoprene gasket is superior.

[Joe L.]

Re: Gas cap finish

Roger----

The original fuel cap for your car, GM #3843576, was zinc plated. Many of these caps that I have seen appear to have been possibly galvanized rather than electroplated. No matter, though, in either case the finish is zinc; just a possible difference in the method of application. When new, these caps were relatively shiny. However, the zinc oxidizes rather quickly and the finish becomes more of a dull gray.

I don't know how your cap became bare metal subject to rust. It may be difficult to refinish in the same manner as original since the cap is an assembly of parts. Originally, the pieces were finished individually, then the assembly was rivetted together.

The current GM replacement cap, which is the original cap for 1968-69 models, is GM #3952708. This cap is very similar to your original cap. One difference is the fact that the original cap uses a thick fiber gasket whereas the 3952708 cap uses a neoprene rubber gasket. Functionally, the neoprene gasket is superior.

[Gary Schisler]

Re: Gas cap finish

I just replaced the cap on my 66 with a repro from Volunteer Products and it is identical to the one I am taking off. It has a bright, semi-shiny zinc finish and is correct, as I read the 66 judging manual. It also has the correct gasket.

[Gary Schisler]

Re: Gas cap finish

I just replaced the cap on my 66 with a repro from Volunteer Products and it is identical to the one I am taking off. It has a bright, semi-shiny zinc finish and is correct, as I read the 66 judging manual. It also has the correct gasket.