I suppose I didn't really answer your question with my first response: I completely removed the entire proportional block and tossed it in the trash.
I copied the majority of my write-up for you to ponder upon. Pluses and minuses to everything, my friend. This thing I did drives a couple of people crazy that I "illegally" removed my brake warning light. These same guys have probably cut out their catalytic converter. Anyhow:
MY SITUATION: Original front disc and rear drums. Height Sensing Valve (HSV) half-assed deleted by PO. Still had 2 old crappy rusty brakes lines running to rear. Acceptable brakes as a whole, but redoing it all because I already have the truck apart anyway and didn't like the rusty, brittle looks of things. Plan is to renovate brake system for added reliability and maybe even get some added performance as a bonus.
I chose to start things off by trying Cruiser54's front Proportional Valve (PV) trash and replace procedure. This seemed logical as a way of simplifying things and perhaps improving front brake performance.. Plus He's got real-world experience doing this and it has worked for him multiple times.
I figured at least to me, that the MJ PV was designed to work a system that included the additional second brake line to the rear (to be used in cases of front brake failure) AND a system including a well-working HSV. Since I now have neither, the MJ PV is no longer being used exactly according to its design with those two aspects missing.
The MJ PV meters the front brakes down considerably after the brake line run into it from the master cylinder. Just look up some of Cruiser54's pictures of those tiny little orifices in there. Remove entire PV and then T-off to your front calipers, using an inverted flare brass T. You should get better braking because the small orifices of the prop valve to the front brakes are eliminated. You're now running near-full opening size of the hard brake lines that are coming off direct from the master cylinder. Makes sense to me so I did it:
and here's a view from side/bottomp:
Now technically I should experience slightly better front brake because I have larger interior diameters running from the master cylinder on through to the calipers.
Because I am eliminating some front and rear "bottle-necking" I used to have at the now-removed PV, I agree with many others here that an Adjustable Proportioning Valve (APV) may be a good idea FOR THE REAR BRAKES. This should eliminate any rear brake lockup that I may experience if I am running a heavy payload. The original intent of this thread was to see where other guys were mounting their APVs. I ended up deciding on mounting mine under the hood after all. Even though TJ1 had a cool location on his rig, I ultimately sided with HOrnbrod's opinion of not having brake lines inside my cab. Mounting near the rear of the bed would likely affect longevity and stable function due to full exposure to elements.
I completely eliminated my two old hard rear brake lines and ran a new single line back there the the axle. So here's where I ended up mounting my APV:
I chose the Speedway APV because it is compact and appears to be simple and tough. Another cool feature is that it allows for full shut down of fluid to the rears, which can possibly come in handy when working on your brakes.
REMINDER: If you've read much on the topic of HSV deleting/PV deleting/running a single line to your rears, keep in mind that you'll lose that safety feature that allows full braking to the rears in cases of front brake failure.
Speedway didn't have comprehensive flow specs on that mini APV that I show in the picture. it shows gpm and max psi and states that it can be completely shut down whatever line it is controlling if desired. I was curious of flow characteristics during "fully open" setting.
FYI for the benefit of anyone interested in this particular device, I sent them a message and here's their response:
Perry, I just spoke with one of my techs and he stated that it will not be fully open when the valve is fully open, there will still be some restriction there.
Thinking around 20% restriction, so it'll flow 80% of the fluid that a straight line will.
As far as I know, we do not offer a proportioning valve that will flow as if there is nothing there while fully open, however the purple proportioning valve might flow a little better as it is not a complete shutoff valve while fully closed, there will likely still be a bit of resistance there.
My brakes ROCK now! Got my MJ running last night and took her for a spin. My brakes were not so bad to begin with. But now they are excellent! Feels like I have 4-wheel disc brakes.
Many thanks to Cruiser54 for the advice on ridding the front proportional block. I have killer good brakes, and I now have the ability to adjust the rears (or shut them down if I choose to)""
1. It took some active shopping around to find the correct sized fittings/adapters to use stock flare fittings and MC orifices with new....I didn't want to have to cut double flares on new and factory brake lines, so I had to use my brain a bit during shopping to avoid cutting/flaring.
2. By design, I certainty now have isolation of from and rear brakes, for sure! Front and rear have two different and very separate paths. They obviously already have two different reservoirs inside your master cylinder. My system continues from there to NOT cross paths with each other. As I had mentioned in my original comment on this thread above, there are advantages and disadvantages to nearly anything you do. I'm pushing full volume to my front brake calipers now instead of dealing with a factory bottle neck. Overall, front-and-back, I can say that I've got superior braking ability compared to what I originally had. And at great cost and time savings. Disadvantage is that I may lose some "fail-safe" capabilities, if you will. I will no longer have a working brake warning light. I weighed perceived consequences, and then decided on my course of action. This method works for me, no regrets.
3. If I lose my front brakes, I still have rear brakes, although the addition of the aftermarket adjustable prop valve doesn't give me full 100% use of the brake line ID. I do not know to what degree my rear brakes assist my stopping if I suddenly lose my front. In my 35+ years of driving, I don't recall ever running into the loss of brakes of either end, so I'm not too worried. I can shut down my rear brakes totally if I want to. If you like to show off and do burn-outs, then this is a nice feature! This isn't me, but I give it as an example. Shutting down rears is also nice if you're working on your rear brakes and want to shut off fluid completely.