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Advance Auto/Carquest for the win! (UPDATE>) Early B Body Gas Cap Problem Solved.

Big Bad Dad

FBBO Gold Member
FBBO Gold Member
Local time
3:18 PM
Jun 11, 2011
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Fincastle, Va.
Hey guys, I'm finally taking time to update on my problem with the new tank on my 64 Fury sucking in badly.
My original thread on this is here> New gas tank sucked in. "Vented" cap? Hmmm... help!

Anyway, after a bunch of research and looking, it seems like just about everybody is selling this "Motorad" brand vented gas cap as being correct for our application.
Well, WRONG! The darn thing has a really strong spring, and does not allow air to enter the tank as the fuel is pumped out. My new tank sucked in so badly, I got concerned it was damaged.. After looking a lot, I found that Advance Auto Parts has the proper cap that works in their Carquest brand. (Part# 10646) I have had it on the car for a couple months now. I am posting pictures of the Carquest cap alongside the Gates "Motorad" cap. I bent the tangs and took the Motorad apart today. That strong spring shot the plastic retainer somewhere up into my garage trusses! My opinion is, you could probably cut the spring down to half, and the cap "might" vent OK. But I trashed the darn thing and hope to live happily ever after with my Carquest cap.
The Motorad/Gates # 31646 cap is on the left, and the Carquest # 10646 cap is on the right in my pictures.

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Thanks for taking the time to post this for us BBD. I’m sure some folks down the road will find this information useful as well.
Doesn't the car have a vent tube going to the tank?
The outside of the Motorad cap looks correct, the other doesn't.
Wonder if a hole could be drilled sideways in the plastic so the spring doesn't matter.
Might pick one up as a spare; as my tanks are the later vented type, that vent issue shouldn't apply.
The old vented caps should say “vented”. Both of those caps have warnings for pressure build up instead, might be an EPA thing. I’m pretty sure the plastic thing on the left cap is a relief valve.
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Yeah, oops - I missed the lettering on the Motorad cap. The contours seem more like OEM though.
I should look at my '69, which has its original cap...