GM Brazil bought the rights to produce I6 engines. They redesigned the 250 (4.1L). Of note is that the head has 12 ports and port fuel injection with fuel rail. Along with a different camshaft, GM Brazil changed the low RPM high torque "tractor" engine into a modern engine but this was only for 4 years '95-'98. Apparently the engine design improvement was not enough to compete in a modern market. So, I hope they sold enough of them to pay back for the R&D and the manufacturing costs.
(Valvoline) On the issue with direct injection (the wording sounds marketing-ish):
"Designers found that GDI (Gasoline Direct Injection) engines don't have the fuel molecules touching the intake valves on their way to incineration in the combustion chamber. Intake valves have seals on them that keep oil lubrication, where they meet the camshaft or rocker arms that press the valves open, from running down their stem and dripping into the intake port. However, no matter how good they may be, a tiny bit of oil still makes its way past and runs onto those intake valve stems. Without gasoline washing them clean, that oil can bake onto the valve and accumulate into carbon buildup."
+++This is an excellent example of a technology improvement that generates an unforeseen problem (too much carbon build-up).
I like logical improvements, with known good payback results, that don't require a major redesign.
