Overheating with rebuilt engine
 

Hey I just started noticing the coolant Reservoir boiling when I rev or drive the car really quick ...I'm gonna change the thermostat but any other ideas would be great

Coolant overflow should not be getting coolant in it until the cooling system pressure exceeds the cap spring pressure (16 PSI, I believe). Verify your cap is opening at the correct pressure and not early

Yea I think it's early but this never happened before

If the over flow tank over flows onto the ground after shutdown, could be the head gasket going. Check the there is no air in the system and that the fluid is drawn back into the radiator when cooled. I had the hose at the radiator develop a air leak that prevented the normal fluid drawback. If you want to check the block thermostat, take it out and heat it to boiling in water. It should be fully open by 190 deg F. Water boils at 212 F. The little jiggle valve goes up when installing. Be careful not the over tighten the 2 screws (or use ones that are too long), the aluminum in the head strips easily. I use a thin layer of silicone as well here. Antifreeze should be 50/50 to 70/30 (antifreeze/water) using distilled water to dilute when 100% concentrate is used. Floating ball testers can be helpful to test what you have in the system now. Never use tap water. Walmart has distilled water for 63 cents a gallon.

If it is hitting normal operating temps very rapidly and really seems to be trying to overheat then double check your timing both mechanical and ignition... start with the ignition and distributor's timing.