Hydroboost install Q's

[BBPanel]

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[saon]

I have a brake help question.
I installed a set up on a '69 impala wagon. Installed the hydra boost (along with the 6.0 and 4l80) from a 2003 1 ton chevy van and the complete brakes from a 5th gen 2010 Camaro ss. Made my own brackets and spacer and got it done.

problem is you can stop the car using your big toe! very touchy and the pedal only moves about 3/4". not very user friendly in the rain on a daily driver. front brakes a lot of dust, more than a stock Camaro, and rears may not be doing much as is.
stock van MC bore was around 1 5/16 or 1 3/8" from what I can find. I switched to a truck master with a 1" bore and zero pedal feel difference.

So I then checked the pedal ratios of the wagon 2.3 to the van 5.5 and a Camaro 3.85.

I did not install a different proportioning valve. wagon was drum/drum car stock.
I am guessing I need a disk/disk generic proportioning valve or a adjustable one in the rear and plumb the fronts direct. and then remount my hydra boost and change the pedal ratio to get a higher ratio in the 5.5-6:1 range?

any other help or suggestions I am open to.

Thanks

[Dragonfly]

I think the bore of the master is your problem , one inch with a hydro boost will make them way too sensitive, try one with a bigger master bore

[Dark Pursuit]

Per the directions on my hydro boost install, a 1 in bore mc will give a sensitive pedal 1 1/8 bore is recommended. (I had to replace the new unused 1 in that I had purchased ) .
Also, a minimum air gap is required at the mc piston to push rod ( .020 to .030 thousands in ) . A dot of clay is recommended for this check.

[RadLS67]

I think the bore of the master is your problem , one inch with a hydro boost will make them way too sensitive, try one with a bigger master bore

Agreed, larger MC bore is needed to work this setup or decrease pedal leverage. Another possibility is to run less pressure from the pump itself.

[alocker]

From your original post you state you tried the van master first then went to a smaller one?

My 68 Impala setup uses a Baer 1 1/8" Master cylinder on an Astro Van Hydroboost. I also use a pump that cam from a van with Hydroboost. The brakes are fantastic. Easy to modulate but tons of power when needed. This is also with Baer disks and their stock compound.

A few things to consider. If you felt no change when changing master cylinder bore, your pump pressure might be too high. Also confirm what pad compound you have, that could be making them touchy. And yes, install an adjustable proportioning valve.

[saon]

I did use the van master first which Its a huge bore, 1 5/16. it has the stock 2010 Camaro ss brembo pads.
thank you for the suggestions. what are my options on how to reduce pump pressure?
also alocker, what is your pedal ratio? I just opened up the center hole and used the stock 4 bolt mounts to mount the hydraboost to the firewall, making a wedge shim to get the hydraboost up as far as I did to get a 2.3 ratio.

[alocker]

I would call a place like Lee's or Turn One to discuss pump pressure.

My pedal ratio is the stock power brake ratio for a 1968 Impala.

I don't know if it's a concern but maybe it's the Hydroboost power unit. There are different ones and mine is from a mid 90's Astro van which has a smaller lower rated accumulator. Maybe a 1 ton van will have the higher rated accumulator and it just provides too much pressure. Not sure how it relates to pump pressure though.