replace head bolts with studs without removing head

A higher tq value for the stud [ v bolt ] does not necessarily mean that the clamping force exerted by the fastener will be greater. Stud probably has fine threads for the nut, which requires more tq to overcome the friction of the additional area of thread engagement; actual clamping force on the head could be the same.
I would doubt that re-torqueing is going to fix a weeping issue because it will take substantially extra clamping force to stop the weeping. May work if the original fastener was under-torqued.