Customer of mine had a rotted core plug in his 440. He gave me shallow brass 1 5/8 plugs. Had a little bit of an issue getting it in (headers) but I thought it was good. Came out the next day and had some coolant in the drip tray. Barely leaks but it leaks. Removed it , when out and bought a steel deep ( 1/2 inch ) Dorman (aka China) and went to install and it also just slide into the block ? Checked the part number on the bag and it is indeed an 1 5/8. Only seemed to tighten up when the last 1/8 inch or so at the edge hammered in. Really don't trust it. Never experienced this before. Are deep plugs on a 440 a no no, or do I just need a different manufacturer freeze plug? I only put water in at the moment and was going to pressure check tomorrow. Thoughts?