The resto shop put in a 4 way Wilwood disc setup on my Charger, but after a huge amount of experimentation that just can't seem to get them working right and now they're hearing from their vendor to maybe switch to manual instead of power. They have tried 4 different boosters. The setup right now is 4 piston front discs and 2 piston rear discs, with an OEM master cylendar, hemi-booster, 1" bore.

I have not tried it myself, but they say the problem is the pedal pressure, there is initial pressure, which then drops an inch and I guess when the pedal is on the floor it's stiff with no movement, though the breaks do engage, in fact so much the engine can stall. All the breaks lines are new and they've bled it to death.

Anyone have this combo working?

What type or perportioning valve are you using...ect..how is your LL plumbed????

Just went through this on a customer car. The solution - Hyrdroboost!

Hydroboost is a hydraulic assist setup that runs off the power steering pump. This has been used on many domestic cars and trucks as an OE piece for years. It allows you to generate WAY more line pressure than ever possible even with a vacuum booster under any circumstances. We sell them here at XV for 875, which includes the line kit and a master cylinder. Forget about the vacuum, and the manual options. IMHO they aren't options...

It's possible that the calipers require more fluid volume than the 1" MC can provide, this would explain the low pedal.

What is the pedal ratio?

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What type or perportioning valve are you using

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You don't need a valve on 4 wheel discs.

I suspect John is right about the MC running out of fluid or the MC is bad and dumping pressure past the piston.

I have 4 wheel discs with the Wilwood 4 piston calipers in front and a 6-1 pedal ratio. I'm running a 7/8" piston Wilwood MC and the brakes are great. I like manual brakes because they are always there and the pedal feel is always the same even with the engine off.

I am no brake expert by any means, but, how do big brake, multi-piston cars like Vipers and Vettes manage to work with regular vac boosters? And if a vac pump is not enough, why would a manual system not work? There is something going on here that does not make sense and it sounds like a mechanical defect, ie; bad M/C or wrong or plugged distribution/proportioning valve.

The OEs can do this with vacuum, because their boosters and pedal linkages have the right amount of assist as well as pedal ratio designed to work with the brake system. Also, OE vehicles have vacuum, with out cammed motors do not, or not enough.

A good place to start is by using vise grips or line clamps. On the rubber hoses by the connection from the metal line clamp all three. (you should have a solid pedal) if not its either the proportioning valve or master. if you have soild pedal clamp the line on the other side and check again.(if you dont have solid pedal) your lines are stretching use stainless steel braided lines. Also oem master is fine but you must make sure it is for disc disc setup or remove residual pressure valve.

Or use brake pressure gauges and find out the real pressure and F/R bias...

Brake pressure gauges only tell you the pressure at the calipers or wheel cylinders, it wont tell you where to start(low pressure= mc,pwr bd,prop vlv,lines,cal,wheel cyn,etc). After piching line at the calipers and you still have solid pedal then you need to look at the distance between the pads and the rotor you should not have hardley any room between them if you do check to make sure hardware isnt binding. Keep the rears pinched while checking the front first. trying to go step by step Thanks

We have seen a lot of problems similar to this and it had nothing to do with the brake system it's self.In many cases it was a bracket alignment or rotor hats that werent seating on the axle flange properly.Make sure your calipers are centered and parallel to the rotor,check the wheel studs to hat hole clearence,you may have to enlarge the rotor hat holes.Make sure the brackets and caliper paralell the rotor.Some times a bent house tube or end will cause you fits.You will have good pedel then loose it.