Race cars often have three (3) master cylinders side by side on the firewall- front brakes and back brakes connected with an adjustable bar connecting the brake pedal arm to the two master cylinder rods, and the third one for a hydraulic clutch. As the gas tank gets empty the driver adjusts the bar and proportioning valve to compensate for less weight in the rear.
I bought a booster and master kit w/mounting bracket, combination valve and residual valves from CPP. Next time I'll probably assemble the stuff myself and save a few bucks, but this time I decided it was worth an extra hundred for someone esle to do it.
There are different dual master cylinders and combination valves: drum/drum, disc/drum, disc/disc.
The purpose of the dual master is to have two circuits, front and back, so that if you spring a leak in a brake line you don't lose all your brakes.
The purpose of a dual diaphram booster is to get more boost for less vacuum, which is what you need with an engine with a 3/4 cam, deisel engines and smaller ones too, like 4 bangers, 'cause they produce less vacuum. So, if you look at a mustang II brake booster, for example, it'll probably be dual diaphragm. In these trucks to keep the stock pedal you need to mount the booster on the frame rail where the original master was, which means you need a smaller diameter booster- 7" dual diapraghm is about as good as you get.
Isusu has an alternator with a vacuum pump mounted to the back of it that they use in their diesel trucks. If I have problems with my set up I'll swap my delco 10si for one of those, since the mounts are the same. Here's one on ebay for $150
http://cgi.ebay.com/ebaymotors/New-...QQitemZ8065888469QQrdZ1QQsspagenameZWDVW There are three valves necessary in a brake system- metering valve, proporting valve and residual valves.
The metering valve is also known as a hold off valve, it delays the pressure to the front brakes a smidge when you step on the pedal.
The residual valves are in-line pressure valves retain a minimum brake line pressure to help eliminate excessive pedal travel in both disc and drum brake systems. The two pound valve is used in disc brake applications where the master cylinder is mounted below the horizontal plane of the calipers and fluid drain back occurs from gravity and vibration, thereby causing excessive caliper piston retraction and a longer brake pedal stroke. The minimal two pound residual pressure prevents fluid from flowing back without causing the brakes to drag. With drum brakes, a ten pound valve is used to compensate for return spring tension in the drums.
The proportioning valve regulates pressure in the rear brake line- You can buy screw type or lever-type adjustible proporting valves to set the right amount of pressure for your system. The proportioning valve does not contain residual valves.
A combination valve does three things usually: It is a proportioning valve, metering valve and sensor for low pressure you can hook a warning light up to. The compbination valve does not contain residual valves.
The last thing that comes to mind with boosted brakes is to use a filter in the vacuum line to the booster to keep fumes from the engine away from the sensitive booster diapragms. NAPA has them on blister cards and so do many FLAPS in their HELP parts line.
