I have used those on engines with CAST IRON intakes.Use a good bolt and thread it down as far as possible,and tighten it.The threads will engage more and hold stronger if you tighten them,instead of just firnger-tightening.But in MY OWN persoanl opinion,there is NO WAY that I would use a lift plate on an aluminum intake,especially a big block.6-700 pounds is really not that much weight.Spread the load out over 4 bolts,that's only a little over 150 pounds per bolt.And what are they,5/16" bolts?You could probably do it and be okay,but I wouldn't with an aluminum intake.Cast iron,wouldn't scare me.Just my $0.02