Although I can't think of why your having this issue with the Holley seals,
Statoseals would work for your application.
All Seals Inc. - The Sealing Specialists
https://www.pegasusautoracing.com/pr...p?Product=3245
Earls Stat-O-Seal Sealing Washers | JEGS
I use them on bulkhead fittings where a normal oring just wont work.
We use them with great success in bladder type fuselage tanks.