Question about tollerances on Dragboat Motor

[Speedin' Ian]

Well my new motor is getting close to completion and of course I am stressing out because I want to make sure everything is perfect. So here is my question. I hear a lot of people talk about setting up marine tollerances on their motors, and I think they mean they are setting them up a little looser because the motors don't generate a lot of heat so the pistons and other rotating parts expand more than the block. Is this correct? If so do the same principles apply to a dragboat motor.
My engine builder has built some boat motors in the past, but definately has more experience building motors for drag racing on the asphalt, so I want to maek sure the tollerances are right.

[Infomaniac]

I give an extra .002 piston to cyl wall.
Mains .003 - .0035
rods .0027 - .003

[Speedin' Ian]

Thanks for the heads up.
Was my assumption correct as to why the extra clearence is added?

[HammerDown]

Because the block runs cooler in a non thermostat marine engine, doesn't expand as much...however the pistons and other internal components pistons etc due to extreme load/heat run hotter and expand more.