RNation0001

iTrader: (2)

ok im finishing up my 5.3 t56 swap into my 67, i opted for a hydroboost setup. car has front disk back drum. i got the corvette master cyl that everyone uses and my problem is that im driving along and i barely press the brake and they lock up. its very hard to keep it from locking up. what can i do to increase pedal travel or reduce pressure so theres a medium between off and lockup

thedrill

iTrader: (1)

I just converted an old jeep to hydroboost and had to put a brake bias valve in the rear brake line to stop it locking up.

It hauled up great after fitting the valve with no brake lock ups.

ls1nova71

iTrader: (4)

I would say the problem is in the Corvette master cylinder as they're for 4 wheel discs. Are you locking up the rear, or all four wheels?

HILROD

You just need to get a larger bore master. The smaller one makes the brakes way too touchy.

RNation0001

iTrader: (2)

its locking em all up. at first it was the back more (i know this is gonna sound bad but its just for testing reasons) then i introduced some air into the back brake system to use the front more and now all four are lockin up at the same time.

if i go with a larger bore master cyl. wont that require less pedal travel though?? cause i already dont have much pedal travel. is it possible to get more pedal travel and make it lock up less??

HILROD

I can't remember which hole my brake rod is in, but the larger master will make a huge difference. On my camaro I use a larger master and have wonderful brakes. On a buddy's camaro, I kept the manual master when it was converted and his brakes are like yours. When he get's tired of it I'll switch to the same master I have on mine.

poorhousenext

What year model corvette master cylinder are you using?

C2's Prior to 67 used a short pushrod

67 C2 & 68 up C3 up use a long pushrod

Hydratech say both of those can be used with front disc & rear drums. Also offer 1.0" or 1.125 MC Bores.

If you purchased as a kit check part number to see if MC uses a short or long pushrod.

They also list a camaro master cylinder speced for disc / drum with residual pressure valve equip for disc/ drum setup.

* GM Camaro Style Master Cylinder
* 1.125” Bore Disc / Drum Spec
* 1/2-20 Front Port – 9/16-18 Rear Port
* 65 / 35 Nominal Front to Rear Output Bias
* Residual pressure valve equipped for use with front disc / rear drum brakes
* 3.400 GM Spec Stud Spacing with 3/8” Bolt Holes
* Features a .250” MC pushrod hole for use with power brake only
* Front Port = Front Brakes / Rear Port = Rear Brakes
* Conventional flare style ports – brake line tube nuts included with MC
Hydro

RNation0001

iTrader: (2)

i believe its the 78 corvette mc.

RNation0001

iTrader: (2)

ok guys thanks for helping me i found the problem. im not sure what the problem was but im goin to say there was air trapped in the hydroboost somewhere. one day i decided to take the belt off and drive up and down the driveway a few times using no help from the hydroboost to see if it went from slight brake to lockup just like when i used the hb. well i did it about ten times and it braked really well with the exception on me having to press hard. after that i put the belt back on and bam. awesome brakes now with no lockup unless i press pretty hard. but now its great i can stop and go without using the manual tranny as the main brake lol. just thought id let everyone who helped me know what the problem was