Usually I wouldn't ask such a stupid question here.

I built an 84 7 a while ago. Has factory power brakes. I put all new brake parts on except for the booster and the factory prop valve.

It has ford f150 disks and calipers in the front and f150 drums in the back... once again all new moving parts. New master as well

I cannot lock up the brakes. the pedal feel is mint. feels like a million bucks.

The booster is working because you can't stop it at all w/ out the vacuum hooked up.

I've run this same brake arrangement w/ a stock yj booster and master... it would lock em up w/ a tap.

What's the deal... is the cj booster/master garbage? or should I think there's something wrong in the prop?

So are you running 44's front and rear, and I am assuming single piston caliper on the front. I would start with basics that you may have checked, like checking brake pads, bleeding the brakes and making sure the calipers are not holding air bubbles, etc.

As far as the booster, the CJ is not that bad, but I think the stock MC sucks balls. I wouod start with a better MC, and get rid of the factory prop valve n favor of an adjustable (if later on you end up throwing discs in the rear). I ended up throwing a Dodge MC on my YJ, and it is a night and day change, and I could do endos on 40's before adjusting the prop valve :D

Hydroboost and some bendix pads FTW!

Actually, I have quite a few factory prop valves seize up inside. One of the Jeeps couldn't get any fluid to one front caliper. My dad's was getting very minimal to both fronts, and it also took a while for the brakes to release after letting up because it had to bleed back through the system, kinda acted like a residual valve... Anywho they come apart really easy, check that, make sure your calipers are sliding on the slides, etc...

-Dave

are the rotors/calipers clean of grease/oil?

I've seen new masters internally bypass, so it could be a defective master.

What's the size of the MC anyway? With stock F-150 2 7/8" Calipers you should run in the 1.125-1.250 range of master cylinders with something in the range of 1.00"-1.125" wheel cylinders in the rear.

It shouldn't have any problem locking up the rear brakes, however locking up the fronts on some rigs is tough on the street. I can't get my GPW's fronts to lock with 37 x 13 boggers on the street but I suppose that's a good thing.

If you are running a factory proportioning valve, I would take it apart to make sure it isn't corroded shut. Most of the factory ones I've seen have been rusted completely shut. The stock one on my Bronco (same brakes as those) had the rear pressure adjusting valve corroded shut so it didn't lower the pressure to the rear brakes. Occasionally if you bleed the brakes the transfer-safety circuit (the sliding block that blocks the flow to a weak circuit via sliding piston) will get stuck.

I would recommend you pull it apart and check it before purchasing new parts. I never run the factory style on swapped shit anyway as it usually corresponds to standard use on the OEM vehicle. If it is corroded, go with an adjustable one.

Face it, the CJ stuff sucks. There is no way around it.

You need more fluid to the brakes, Replace the master with something bigger, like what ever ford master people are using or the booster version of the corvette master and your brakes will have rock solid braking power. Both will bolt to your current booster.

so the prop valve could get blocked up or something like that? The pedal is hard... like I'm pushing fluid hard against something (not the calipers and wheel cyls though.

I guess I'll tear that out and see what the dea is. otherwise I have a 1 ton ford master I guess I could try.