Let the engine warm up and tighten the cap screws with an allen wrench.

You'll find that you'll be able to turn the screws another 1/4 turn or so without a lot of resistance, beyond that it requires quite a bit of force.

You'll want more force than you can apply with the short arm of the allen wrench, but less than the maximum you could apply with the long arm.

I don't know what the actual torque figures are.

It is typical for cap screws to come loose, particularly on engines that have never had this done.