We have used qute a few sets....the quality was decent at first...that of which would be comporable to a procomp head. Than on 4 sets of there SBF heads we built a mild 347 stroker...410hp and cracked 4 sets a row on the dyno! Right above the head bolts on the rail. The BBC heads had there share of problems as well as the Vortec heads we had to retool. Stay way IMO unless you buy bare and have some install quality parts and machine them right.