I re-use the blocks, too. But the copper washers are readily available so I replace them. You are right about the copper washer making the seal where they are used.

"It's just a phase. He'll grow out of it." Mama, 1964

1956 Chevy 1/2-ton 3100
1953 Chevy 6100 "The Yard dog"
1954 GMC Suburban Now with a new proud owner.