SD7 adapter not sealing

[KUL FIR CHICK N]

Vintage Air would definitely know better than a shadetree like myself would on whether the washer is needed.

Those are "dual slim line" seals (DSL). We used DSL and SSL on the '16-22 Ford GT system and we use "single slim line" (SSL) on our Gen 5 TXV, but the SD7b10 compressor uses its own kind of oddball design "o-ring face seal" (ORFS) o-rings. They seal well and are reliable, but they tend to fall out and get lost when you open the system.

OK, that's enough nerding-out on AC seals for one night....LOL.