explorer 8.8 in an a-body: experience needed
Based on the article above, those of us putting an 8.8 with discs where there were drums should be making sure we have no residual valve. I've read everything I've seen on the 8.8 swap here and not seen this discussed.
I agree, because if I remember, the residual pressure check valve is needed to keep aout 8-10psi on drums to prevent dirt and debries from entering the brake system through the wheel cylinder.
I was once considering an 8.8 swap and retaining my front drums till I can afford a BBP disc swap.
To do that, I would need a an inline proporting valve (adjustable) to control brake bias, as well as an inline metering valve to keep the discs from activating untill sufficent pressure (60-80psi) is on the drums to overcome to springs to prevent the rear wheels from locking up under hard braking. Lastly the MC would have to be changed because on vehicles with 4-wheel drums, the residual pressure check valve is built in to the master cylinder and the residual pressure on the rear circuit would cause the brakes to drag back there.
Moreover a vehicle considering this swap with front disc brakes, adding the 8.8 with discs to the rear would eliminate the need for a residual pressure check valve as well as a metering valve. The only thing required would be the adjustable proportioning valves on both circuits.
Residual valves don't have a damn thing to do with keeping dirt or any other nonsense out of the brakes or wheel cylinders, and residual valves aren't used with drum brakes, please do not advise anyone on brakes, YOU are going to get them KILLED...
Prop valve is different than a residual valve, there are many different residual valves...
Drum brakes are ADJUSTED and held within a measured amount from the drum by a slack adjuster at the bottom between both shoes, the springs hold the shoes together and push the pistons into the wheel cylinder and that gives you that amount of throw on the master piston to move enough fluid to activate and work the brakes... This adjustment also helps warn you when they need adjustment as the pedal will no longer be high and firm..
Now you add discs into a drum disc system and what happens is everytime you release the brake the piston in the caliper retreats, it does so by the rotor bumping the pads and instead of the caliper floating with the pads over the rotor the piston retreats to far and you have a problem, now without a residual valve holding some psi on the line it retreats to far and the pads become to far from the rotor and then when you hit the pedal you do not get the right amount of psi on the piston BECAUSE you do not have enough fluid flow for the amount of piston travel in the master and that in turn has less force on the pad and that in turn has YOUR front pads now doing 90% of the work all the time, and you THINK you have rear brakes...
I didn't go thru all of that because you know, i went thru all of that because i know you don't know and thats why i bothered to interject to the unknown of how brakes work since i seen NO ONE knew..
Now you do, and you NEED a residual valve.
I answered the op also, whether or not you like the answer is another issue.
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