Like the GM 4.2 liter inline 6 that was in the Trailblazer? At the time I was working for a company that made the leak test equipment for the lost-foam casting blocks for those. Once they 'gross' leaked (porosity in the foam casting) they sent them into a secondary process to seal the pores. They were allowed to fail three times (being re-cycled thru the sealing process) before they were scrapped. Oil was leaking out of the sides of the engines....