A radiator filler neck is a cap opening that is installed in between the upper radiator hose fitting and the fitting on the engine. It allows  you to fill up the cooling system with coolant by removing the cap. It usually has a pressure cap and is secured with hose clamps.You have finally finished that sweet engine swap, everything is assembled and you are now in the testing and tuning phase. You now have one last problem to diagnose - OVERHEATING!.You have the big aluminum radiator, the g … read more