.....

 

head gasket no doubt ur oil may not be mixed with coolant but it can still be blown does ur cars overflow back up with coolant

 

does it run like complete ****??? Blowing white smoke a lot out of tail pipe?????

head gaskets id go with


best case scenerio...u didnt bleed the system properly when doing the intake...and u have a big air pocket trapped in the system

 

Or you can double check the thermostst and make sure you didnt put it in backwards.That will do it,good luck