I swapped from my chevy double hump heads to AFR 195CC. I now run about 20 degrees hotter according to my autometer gauge. The car runs about 210 with the griffin 31x19 1-1/4" tubes. I think this is still a little warm. My guage on the speedo reads about 160, that sensor is located on the intake manifold on the miniram instead of on the head like the original one.

 

You might just be making more hp, what kind of waterpump do you have?
Aluminum heads are over-rated in my opinion. For the price they aren't worth it. What happen swith al. heads is all thermal. If you had 2 identical heads only one was iron, the iron would make more hp with less timing and less compression. The aluminum heads loose energy through it's material and is why you have to run more compression to get the same power. A better way to understand is is like trying to have a really hot furnace to melt sand into glass. Would it make sence to put heatsinks all over the outside of the furnace if you were trying to keep the heat? Anyways, the advantage of al over iron is weight. I would love to have al heads with a thermal shield insert or coating. Same stuff they use on top fuel and HO racing engine pistons. The hotter the burn the better expansion properties results in greater force.
This is probably why the better flowing fastburn heads only make 8 more hp than the smaller vortec heads with less compression, the hotcam and a standard 350 shortblock (same intake).
So if GM is reading this, vortecs good, fastburns are a rip.
What kind of power are you pushing?

 

Not to mention the coefficient of expansion of the two different materials. Something about torqueing a bolt to the point of breakage still worries me.

 

I have a edelbrock victor series water pump #8881. I'm beginning to think that the coolant passages are the problem and need to be enlarged. They look like someone chiseled them. They are much smaller than my old chevy heads.

 

All things being equal, you'll always need more cooling capacity with aluminum heads. Aluminum is like a little heat sponge. It sucks it up from the combustions chamber and gets it QUICKLY to the coolant. Effectively, it does run hotter. Assuming your cooling system is adequate, however, your operating temp should always be within a few degrees of your thermostat temp, regardless of what heads you run. The thermostat is the regulator. If the radiator or the water pump isn't up to the task, however, THEY become the regulator and that's when you start to flirt with overheating or temps continuously well above the thermostat temp.

 

I have a 180 thermostat with two 1/8" holes drilled into it.