I had a slant six in a 1966 Dodge van, and that thing went about 100k miles between and oil change! When we did change it, it came out like sludge, but...damn, that engine kept going! (I am exaggerating, it wasn’t 100K, but it was far more than any rational person would attempt...:)
LOL, NOTHING could destroy those old slant sixes!
I bought mine for $100 back in ‘82, and the engine had a rod knocking in it that was ready to punch through the cylinder. So me and my buddy got an engine winch, I bought another 225 with the tranny still attached, called up a few gearhead friends, and had an all-nighter engine swap party. Pulled the hood, dropped the driveshaft, unhooked everything, and dropped the new one in. Couldn’t get the damn thing to start to save our lives until one genius (who was an actual, paid mechanic for Walmart) discovered that whoever had worked on it last dropped the distributor in backwards, and the timing was 180 degrees off. LOL Ran like a champ after that. I had to firewall it on the freeway to make the speed limit, but it got me where I wanted to go.