Trying Hydroboost, much needed advice PLEASE

[BillySS]

I just purchased a manual brake set up from TRZ. I hate it!! It took me until the last turnaround at Etown to get it slow enough to make the turn. Anyway I just purchased a remaned Hydroboost booster from an earlly 80s regal/monte carlo. I also just ordered the new lines from Rockauto. Any advice and tips on what else I need to convert my brake system???

 

[t5montecarlo]

Did you raise the pin on the brake pedal to the hole for manual brakes?

 

[BillySS]

Yes 1" above factory hole.

 

[BillySS]

I did some reading in the forums and some people say to get rid of the stock PV. I bled the brakes at least 10 x and then again when I got to the track sunday. It seems like its using more of the rear brakes to stop. I did put the front brake lines in the rear port on the master like the instructions say.

 

[malibudave1978]

What is your brake system setup? Stock front calipers and stock rear drums?
What size brake master cylinder are you using?

Stock size calipers have a 2.38 piston and are quick take up calipers after the 1981 model years for g-bodies. This size is small for the size of our cars and the quick take up design requires a step bore master cylinder. These calipers should be upgraded to a oversized 2.75" piston. These oversized calipers are not quick up design. Even though the caliper is upsized from 2.38" piston to a 2.75" piston, it still would only need a 7/8" master cylinder or less.

There is a 15/16" master cylinder from a dodge dakota that can easily be adapted to the TRZ manaual brake set up. But I still think it is too large of a master cylinder. There is the step bore master cylinder from the s10 with a 24mm primary bore and a 1 1/4" step bore, but I think this is too large for a stock g-body braking system or with the upgraded larger calipers. This master cylinder would require modification (elongating the mounting holes) to bolt to the TRZ manaul brake plate.

Stock g-body manual brake pedal ratio is 6:1
TRZ manual brake pedal ratio is 5.5:1
Stock g-body power brake pedal ratio is 5:1

The higher the ratio = less pedal effort and more leverage to get fluid to the caliper.
Smaller the master cylinder = less pedal effort and more pressure to the caliper.

 

[BillySS]

It's the Strange master with 1.032 bore. I raised the pin hole 1" over factory according to TRZ instructions. I also have SSBC dual piston front calipers on drilled n slotted rotors factory drum in rear with GN High Boost wheel cylinders.

 

[malibudave1978]

What is the bore size on those calipers? Are those calipers used on the stock rotors and spindles?

IMO, I would step down on the size size of the master cylinder. A master cylinder from a 1995 Dodge Dakota has a 24mm or a 15/16" bore. If you have a choice choose the smaller 15/16" bore. You should be able to get this master cylinder new from the auto parts store. I don't know if you run brake line adapters on the Strange master cylinder, but the Dakota master cylinder has 1/2-20 and 9/16-20 outlets. G-bodies have 1/2-20 and 9/16-18 outlets. You will need an adapter to convert to the GM brake line fittings.

 

[BillySS]

I will look into it Thx

 

[LS6 Tommy]

It's the Strange master with 1.032 bore. I raised the pin hole 1" over factory according to TRZ instructions. I also have SSBC dual piston front calipers on drilled n slotted rotors factory drum in rear with GN High Boost wheel cylinders.

IMO you may not be building enough pressure for manual brakes, especially since that master is designed for a disc/disc setup, not disc/drum. I'd go to a smaller master, maybe even as small as 7/8".

Tommy

 

[malibudave1978]

It's the Strange master with 1.032 bore. I raised the pin hole 1" over factory according to TRZ instructions. I also have SSBC dual piston front calipers on drilled n slotted rotors factory drum in rear with GN High Boost wheel cylinders.

IMO you may not be building enough pressure for manual brakes, especially since that master is designed for a disc/disc setup, not disc/drum. I'd go to a smaller master, maybe even as small as 7/8".

Tommy

Tommy,

Is there any other low cost 7/8" aluminum master cylinder alternatives? I know there is some aftermarket units, but they seem to be $180 and up. I know of some mopar style 21mm and 7/8" bore MC, but they have small 3/8-24 line outlets.