! One concern I had with the valves is they might need the hydraulic pressure to actually make the spool shift.[/QUOTE]

I surely don't know a lot about such matters, but I think the spool will shift due to the magnetism of the solenoid, not the pressure. Not at all sure of that though. A few years back I built a system for an old Ford 7.3 for not much money. Spent a lot of time reinventing the wheel, but eventually it worked fine. Keep us posted.

__________________
John Schroader
bio burnin' 83 300D, '83 300 SD, '79 240D
"I've never met a man who was good at making excuses who was good at anything else" Ben Franklin
"You cannot permanently help a man by doing for him what he could and should do for himself" Abraham Lincoln