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Like I said in your thread. I appreciate the effort but this was unnecessary.
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Plenty of people ask Hydroboost questions from time to time and in this forum there really isn't a thread for it. It only seemed appropriate. Wasn't trying to come of like an a$$ (though I probably did), just realized there might be a need for an informative thread that wasn't project specific.
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In relation to my truck. I'm running a 14 bolt ff rear w/drums and an 8 lug 3/4 ten bolt front. Both with new brake parts. My pedal is pretty stiff and seems to have little assist. The vacuum source is the big port at the back of my 600 cfm edelbrock carb and has plenty of vacuum present. I got the booster/proportioning valve/master cylinder set up that was recommended for disk/drum. The pedal has never felt like it had much assist. Although the pedal feel in my other truck takes some getting used to, it stops that fat pig pretty well. If I had to stop the '57 in a hurry id be in trouble.
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Lotsa stuff that can come into play. Without specifics I can only throw out general advice.
If you're using an aluminum master cylinder from a newer vehicle then it's probably designed for "quick takeup" calipers. It's supposed to reduce drag on the rotors but the design really slows pedal application. It seems to take for-ever to apply and then you (well, I) don't feel much assist when they hit. Switching this type master for an older iron version usually makes for better pedal feel but it can increase pedal travel, too.
If your truck has 73-87 front calipers there are a couple of different size pistons available. You want the largest pistons to reduce effort at the pedal. If you accidentally ended up with 1/2 ton calipers (they bolt up) then you've got 2.94" pistons. 3/4 ton calipers are 3.15" diameter and make all the difference.
GM used the same basic rear drum on the 14 bolt 3 1/2" X 13" brakes from about '70 to at least '02. There aren't many variations. Like calipers, larger diameter wheel cylinders make for less effort at the wheel. One ton dualies usually have the largest wheel cylinders so if you're using the 1" or 1 1/16" cylinders you can move up to the 1 3/16" version for better rear braking.
On the master cylinder side you want a smaller bore to create higher pressure and reduce pedal effort. The tradeoff for all of this is in the distance the pedal has to travel before it builds pressure. If you're not careful you'll end up with a system that doesn't build a pedal until it's halfway to the floor when it's fully adjusted. And it gets worse as the brakes wear.
Master cylinder, caliper, and wheel cylinder sizes are published in many brake catalogs although that information is getting harder to find. Sometimes it takes some digging on a manufacturers' site or at the part store to get it. I do have several references at home and am happy to look up dimensions from time to time.
HTH