After purchasing our 51 3100 1/2 ton a couple of weeks ago I decided to do a fresh oil change. The motor is an upgraded 253 from a mid 50's sedan. What has got me perplexed is the contraption at the drain plug and I am wondering if anybody has seen this before? Clearly aftermarket. Its not a petcock. if I remove the screw it is not threaded all the way into the drainplug. Then you can see the adaptor as well. Is this some type of anti back out device? the center drain plug has an o ring on it and not a gasket. Curious what you all think.
