how much heat would the collision of two c-class asteroids produce?

I know it will create or at least release some. "4 Vesta  has been
studied recently with HST." "There is a gigantic impact basin so deep
that it exposes the mantle beneath Vesta's outer crust."

The simulator at:
http://spacetethers.com/spacetethers.html

in examples 68-70 has asteroids hitting earth and how much energy 
they have.

you need to know the velocities and masses of the two asteroids and
how they collide.  for a perfectly inelastic collision, you conserve
momentum and depending on the angles of impact may need to do some
vector math to find the momentum of the resultant asteroid.  you would
then find the energy of the origional asteroids (ke= 1/2* m* v^2) and
subtract the KE of the resultant asteroid.  this is the energy lost to
heat.

also, I am not sure how much I remember from astromony but isnt class
3 simply reffering to carbonaceous?  to me it sounds like the
calculations would be very messy because you could not really have a
near perfect elastic or inelastic collision, some more context would
help

Neato, thank you both for the info thus far.

I guess...well, let's assume that the two class-c asteroids (you are
correct, they are caronaceous; I chose class-c simply because they are
the most abundant type)are perfectly spherical, 1 kilometer in
diameter, 500,000,000,000kg and impact at a velocity of, oh, lets say
20 kilometers a second.

To add, my original question -I now see- is flawed. Whereas I thought
the mantle of vespa was glowing from the impact, it actaully appears
that vespa has a molten core and that the impact simply exposed this
already heated interior. Nonetheless curiosity still remains.

Again, thank you. And Proz, I apprieciate your taking of this
low-value question and on the NEW YEAR! very cool, very. I was your
last comment of 2003 and first of 2004!
(pacific standard time)

Another thing not to forget about is rotional enegry (both about it's
own center of mass and about it's "instant zero"