I've just finished building a twin turbo lq4 motor and the car over heats at idle. I can't figure out what's wrong and don't want to just start throwing parts at it. It's a fully forged 408 iron block with ported 317 heads, ls9 head gaskets and arp head studs. It's got a replacement ls1 water pump from advance auto that was on my old motor and doesn't leak with a brand new slp 160 thermostat. It's got a two year old radiator cap. The car also has a Kurt urban vent port kit. The car doesn't burn coolant and there isn't any in the oil either. I have a brand new griffin radiator with a puller fan and custom shroud. My tuner said the car appears to be running to well to be a cracked block. I'm lost and don't know what to do. Any thoughts would greatly help!

 

Also both hoses from the water pump are hot. When the car overheats it doesn't appear to be boiling out or overflowing the reservoir. The belt does occasional squeal when you rev the car but it's a new belt and has plenty of tension. This may seem out there but I did rattle can the pump black. Could over spray getting on the pulley cause more slippage and overheating?

 

Wrong section move to force induction section

 

Yes please.