[Caprimaniac]

Same here. But used a drill instead of the hammer. Made holes in the aluminium valve covers and then glued ("TruWeld"? petroleum and heat resistant) and riveted 1/2" x 1/2" x 1/4" alu pieces on the inside of the covers. No leaking- still after 4 years. It's also well hidden- not easy to spot.

Rune