Weird pedal feel, low vacuum??

[TheChief]

Hey guys,

I have a set on wilwood 6 pistons up front and 4 on the rear, all running on the 12.2 in drilled and slotted rotors. The master cylinder in a Detroit speed master/booster.

So far been very underwhelmed, the pedal feel is very off. On long straights where there is little need for braking, when I come to brake the pedal is soft and the brakes are snappy, under heavy braking in twisty roads the pedal is very hard and brakes are soft and unresponsive.

Could this be low vacuum/vacuum leakage? or does it just need a good bleed, or both...

It's powered by a 383.

Any help would be much appreciated as I don't feel entirely safe driving it

Cheers

Jonny

[Sieg]

Engine idle speed and manifold vacuum at idle?

Pedal ratio?

Proportioning and residual valves?

Bleeding method(s) and number of times?

Type of front and rear caliper mounts?

[WSSix]

The vacuum booster assists in applying the brakes. Low vacuum would make the pedal harder to push as if you had manual brakes.

This sounds like a bleeding issue. Sitting in the drive way, can you pump up the pedal? By that I mean, press the pedal steadily repeatedly. Does the pedal get harder? If so, you have air in the lines. From your description, this is the first thing I would check. Sometimes, you can have a tiny leak that wreaks havoc on your system. Or, it could simply be a system that's going to be difficult to bleed.

[FETorino]

Bleeding the brakes again would be a good starting point. Did you bench bleed the Master Cyl when you installed it? If not I'd start there and then rebleed the whole system.

[Sieg]

Originally Posted by FETorino

Bleeding the brakes again would be a good starting point. Did you bench bleed the Master Cyl when you installed it? If not I'd start there and then rebleed the whole system.

+1