Otto,

FWIW, here are some pics that add info to the "filler cap" mystery. Thanks Bill H. for your input!

1st pic is noted to have been for a 1931-42 Chevrolet cap with the handle, which is what was apparently used on the '51 GMC I grabbed a pic of. Would not have been a "stock" item on the '51 GMC engine.

2nd pic is of two slightly different GM NOS oil filler caps noted to be 1931-62, GM part number 836450 which I confirmed using GMpartwiki search as the same number for both Chevy and GMC.

The 2nd pic shows the cap with just a cork seal. Whatever baffle material was down inside the draft tube itself remains a mystery to me at this point.

Dan

EDIT: Tom's pics of the "Closed" road draft tube system was an option to the open road draft tube setup on these engines. Thanks Tom for your input too!
Attachments
1931-42 GM oil filler tube cap with handle.png (211.69 KB, 138 downloads)
Handled filler cap
1931-62 NOS draft tube oil filler cap without handle.jpg (11.19 KB, 140 downloads)
No handle filler cap

Last edited by Gdads51; 04/25/2023 5:13 PM.
~ Dan
1951 Chevy 3 window 3100
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