Gary49eight wrote:
Sorry, I just don't get it. I cannot fathom the idea of using oil like 10W30 in one of these old bangers. I am sure the teenager at the parts retailer thinks it is good oil, yes it is, for a 2020 engine. As Scotty from Star Trek kept reminding Kirk, ye cannae change the laws of physics. The physics here is called Couette Flow, which in a nutshell means the greater the clearances the higher viscosity oil you need. More recent engines have much smaller clearances, so they can use lower viscosity lubricant, this reduces bearing friction. Engines made 70 years ago were never intended for anything less than 20W50, unless you are north of the Arctic Circle.
The lower viscosity oil will escape more easily from hydraulic lifters too. maybe that is the cause of your lifter rattle. If anyone has been running a Packard engine on low viscosity oil and tears it down for a rebuild, please post photos of the crank and bearings. Additionally hydraulic lifters don't like gunk in them, so one suggestion is use Diesel engine oil. Diesels are filthy, so oil for them has a high detergent content. You will be unlikely to get blockages in the lifters or galleries. Avoid the low viscosity 'water", this is poison.
Gary (mechanical engineer)