A guy asked me why the 4.1/4.5/4.9 and the Northstar don't have freeze plugs. It seems he was worried about cracking the block if he ever had the coolant freeze...Here's the real deal...They really aren't freeze plugs. Those plugs that people call freeze plugs are really plugs that seal up holes left in the block casting by the sand cores. The cores need support during the casting process...they are supported via extensions on the core that leave the holes in the side of the block... So, those holes have to be plugged. The holes are machined and the cup plugs are pressed into the holes. I have no idea where the idea that they are freeze plugs came from. I suppose that someone looking at them figured that they would pop out if the block coolant froze and protect the block from cracking. Unfortunately, if you test this theory you will find that the block will still crack when the coolant freezes. The plugs are really core plugs...not freeze plugs...so not having them on the 4.1/4.5/4.9 or the Northstar does not put you at a disadvantage. I hope this clears up what is one of the most common bits of misinformation about your engine.