I found a '86 225 with approx. 77,000 miles on it for my '73 Dodge Powerwagon. I had it installed and am trying to get the kinks out. One disaster that I encountered is when I changed the oil (black in color after 251 miles). When I started it up, my oil pressure went up to 10 lbs. and then it started to drop back to zero. I figured it was just a loose wire on the sending unit until it started knocking. After I quickly shut it down, I observed a 'lake' of oil under the truck which turned out to be from a bad seal on the oil filter. The previous gasket was stuck onto the oil pump and was perfectly centered. I even wiped it off with a rag before I put in the new filter. ALWAYS make sure the old gasket is removed!! It's been throwing a lot of blue smoke (even before the mishap with the filter) but stops after a few minutes. Do you think using something like Mobil 1 or Castrol 5-50W or 15-50W would hurt it?? I'm currently running 15-40W Rotella Oil in it now. Any suggestions would be GREATLY appreciated it!! I don't want to go through the expense of putting another engine into this and I really like the benefits of synthetic oil. Have a GREAT Day! Kevin

Oil smoke to me sounds like valve seals are worn or missing. As far as synthetic oil goes, I am a firm believer in Mobil 1, but you may end up using more oil than normal if you use it. The 5w-50 would be too thin and may cause oil leaks or not be heavy enough viscosity for an older engine like the slant. Plus if you're changing your oil every 3k anyway its extra money spent for little gained. I would stay with a conventional oil like Castrol GTX or Valvoline 10w40. If it was a fresh rebuild with tighter tolerances than original specs, I would use the Mobil 1.

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"That thing gotta HEMI in it??"

I also think it's valve stem seals, pull off the valve cover and take a look. If the stem seals are hard and / or cracked, that would do it.
The good news is that you can replace these from the top if you get the proper spring compresser.
DD