Help with a Proportional Valve

[iriegnome]

Ok. I am on my third proportional valve. Not sure exactly what goes on inside these, but they send fluid to the front and rear brakes in the correct level from the master cylinder. Problem... There is a side cap/cover over a little rocker and a couple of valve like pistons kinds of things.
Mine was leaking out of this cover. Replaced it. It leaked again. These both are aluminum block proportional valves. My father-in-law had a cast iron proportional valve that I put in. No leaks and it seems to be working. What are the differences between these? I think the CI version came from an older 89 or so. Mine is a 92.

[bravekozak]

The goal is to have the front brakes lock up a fraction of a second before the rear brakes. The best way to test this is to have a third party observe your wheels while you slam on the brakes in front of them. Brake modifications and different wheel/tire sizes both have a big effect on this. The best proportioning valves are adjustable. Factory proportioning valves are perfect for stock brakes + stock wheels and tires. They have built in restrictors for the rear brake lines.

[iriegnome]

So what would be the difference between the one I took off my car - the aluminum housing with the valve/rocker thing on the side and the one I put on that is just a cast body with holes in and out and 2 holes plugged?