55.2-59 Flat Out Engineering brake question

[Eagletucky]

Hi guys,

Looking to see what others have done on here regarding a master cylinder/booster combo after installing the Flat Out Engineering C4 corvette upgrade. I performed this conversion last year and have not been able to figure out a combo that works. I would love to hear what others have done.

I already bought the brake master/booster combo "kit" from Flatout. it didnt work well at all, so im trying to see what other solutions are out there.

Thanks in advance,

[mick53]

I would get as many spec's on the calipers as I could and call Wilwood tech line. They will fix you up on both. When I designed my brakes from scratch they were awesome.

[mr48chev]

I'd say that Mick53 gave about as good of advice as you are going to get.

[svr]

I followed Ogre and went with a hydroboost system in the stock location under the floor. Other than a few trips around the block not a lot of experience but so far i love it. If i remember right the master and booster come from a cobra mustang.

[ndeep]

you did not say what engine you have. i have a 495 horse ls3 crate and my brakes were horrible, engine does not have enough vacuum to support power brakes. since i already had the master cylinder and booster i opted to go with a reed vacuum pump.works great now.

[Eagletucky]

Originally Posted by ndeep

you did not say what engine you have. i have a 495 horse ls3 crate and my brakes were horrible, engine does not have enough vacuum to support power brakes. since i already had the master cylinder and booster i opted to go with a reed vacuum pump.works great now.

Good question. Sorry I didn’t think to include that info. It’s basically a stock 5.3 with a really mild cam. Vacuum isn’t a problem, I’m always near 14 inches when driving.

[daveshilling]

Originally Posted by Eagletucky

Good question. Sorry I didn’t think to include that info. It’s basically a stock 5.3 with a really mild cam. Vacuum isn’t a problem, I’m always near 14 inches when driving.

Well if you want a setup that's definitely going to work, install a C4 master/booster on the firewall...It's not the prettiest but it was designed for C4 brakes, so it should do the work. I contemplated the C3 master booster (what the universal kits are designed after) but I might just crack at the hydroboost first.... I like the idea of short pedal travel and a hydro sounds like it will offer that. Then I can chop the factory pedal.

[daveshilling]

Originally Posted by svr

I followed Ogre and went with a hydroboost system in the stock location under the floor. Other than a few trips around the block not a lot of experience but so far i love it. If i remember right the master and booster come from a cobra mustang.

Yeah I started down this path too, until I realized that we're running a Ford hydro to a GM rack...others are running this to a Tbird rack so its all Ford and pressures differ by OEM.

Interested to hear about your experience with this before I start over with these brakes!

[1project2many]

Hi guys,

Looking to see what others have done on here regarding a master cylinder/booster combo after installing the Flat Out Engineering C4 corvette upgrade. I performed this conversion last year and have not been able to figure out a combo that works. I would love to hear what others have done.

I already bought the brake master/booster combo "kit" from Flatout. it didnt work well at all, so im trying to see what other solutions are out there.

Mick53 gave great advice. Collect information about the currently installed components and contact pros.

There is soooo much that goes into the braking "experience" that it's not funny. I would ask you to consider what you want to happen that isn't. Are you looking for reduced pedal pressure, faster response when in traffic, brakes that you can abuse more? Many folks seem to judge by initial pedal pressure and stopping distance at low speed. Quite often you can change pads and rotors and see dramatic improvement. More aggressive "street" pads and rotors are often better at short distance and cold stopping. Pads designed for towing, fleet use, or racing often require more heat before they stop well so they don't always feel like good pads in traffic. Their strength is in being able to stop when components are very hot.

C3 corvettes had four piston calipers with a huge amount of surface area. The power brake master cylinders used with these systems were 1-1/8" diameter. All C4's use master cylinders with smaller diameter bores. Some used a smaller pedal ratio but it appears that pressure at the caliper is greatly reduced at the caliper if the Flat Out master is the same as the C3 master cylinder.

There are ways to upgrade the C4 brakes to 13" rotors as well. This is another tool to put "better" brakes in your truck. This requires adapters and brackets and new calipers. Is it the right approach? Hard to tell...

My advice is to collect as much information as you can in order to make an educated plan. Get the master cylinder diameter. Get the year of your calipers as well. If you know what pads are installed that would help as well. Whether you call the pros or continue to post here, this information will be critical.

------------------------------------------

I like the idea of short pedal travel and a hydro sounds like it will offer that. Then I can chop the factory pedal.

I've done a couple of hydro swaps but the results weren't quite what I wanted. Braking was improved and I could really muscle the vehicle around better, but I wanted reduced pedal effort during light stops and that didn't really happen.

Most of the GM Hydroboost master cylinders I can find use a 1" diameter piston. When you replace the smaller piston of most stock masters with the 1" piston you reduce pedal travel but you lose a bunch of force at the wheels. I suspect GM applications with both HB and vacuum brake options use a pedal with the master cylinder push rod connection located closer to the pedal pivot for HB. Moving the connection would increase pedal travel and decrease driver effort.

With all that said, I believe Ford HB units use a smaller piston. Much more likely to create a significant reduction in pedal effort. How much pressure difference exists between Ford and GM power steering systems?

[_Ogre]

Originally Posted by Eagletucky

Hi guys,

Looking to see what others have done on here regarding a master cylinder/booster combo after installing the Flat Out Engineering C4 corvette upgrade. I performed this conversion last year and have not been able to figure out a combo that works. I would love to hear what others have done.

I already bought the brake master/booster combo "kit" from Flatout. it didnt work well at all, so im trying to see what other solutions are out there.

Thanks in advance,

brake systems are pretty basic, but probably cause the most aggravation
without me googling it, what is the flat out c4 upgrade? drive train or just a mc?
what hasn't worked?
what have you tried?

[daveshilling]

Originally Posted by _Ogre

brake systems are pretty basic, but probably cause the most aggravation
without me googling it, what is the flat out c4 upgrade? drive train or just a mc?

Swapping the front and rear suspension and power rack from a C4 Vette into a truck using the Flatout engineering kits.

You end up with a GM rack, which is why I haven't finished my Ford Ogreboost yet... I've seen conflicting info on whether they will work together / how they will work together.

[_Ogre]

Originally Posted by daveshilling

which is why I haven't finished my Ford Ogreboost yet... I've seen conflicting info on whether they will work together / how they will work together.

you haven't finished cuz this ogre has trade marked the Ogreboost™

truk uses gm pump with tbird rack and 03 ford hydroboost. if i had it to do over, i would use the ford pump matched to the tbird rack. my steering was always 'twitchy' oversensitive steering, no good way to explain it. it just didn't feel right at 50-100mph. i fixed it with the speedway flow reducer and it's good now. i don't thing the hydroboost gives a rats petootie about pressure or flow

also if you use the ford hydroboost under the floor, get the mc reservoir and adapters off the nissan quest or mercury villager. mounted on the firewall, instead of under the floor makes it easy to see when you have a problem

[daveshilling]

Originally Posted by _Ogre

you haven't finished cuz this ogre has trade marked the Ogreboost™

truk uses gm pump with tbird rack and 03 ford hydroboost. if i had it to do over, i would use the ford pump matched to the tbird rack. my steering was always 'twitchy' oversensitive steering, no good way to explain it. it just didn't feel right at 50-100mph. i fixed it with the speedway flow reducer and it's good now. i don't thing the hydroboost gives a rats petootie about pressure or flow

also if you use the ford hydroboost under the floor, get the mc reservoir and adapters off the nissan quest or mercury villager. mounted on the firewall, instead of under the floor makes it easy to see when you have a problem

If the pump and rack are what need to match, then I should be good to go! Just need some $200 lines now. I did get that MC reservoir per your prior recommendation. I thought about mounting it on the drivers side where the factory floor jack is usually located... I just need to figure out hoses to route through the cab somehow.

[daveshilling]

Leaving this here to possible aid in the discussion:

'85-'87

MC Bore .875"
Wheel cylinder bore 2.1" front 1.6" rear
Pedal arc ratio 3.5 to 1
Line pressure with 100 lb on pedal 1250 front 800 rear

'88-'91

MC Bore .87"
Wheel cylinder bore 1.5" (dual) front 1.6" rear
Pedal arc ratio 3.5 to 1
Line pressure with 100 lb on pedal 1250 front 750 rear

'92-'96

MC Bore .93"
Wheel cylinder bore 1.5" (dual) front 1.6" rear
Pedal arc ratio 4.0 to 1
Line pressure with 100 lb on pedal 1160 front 680 rear

[1project2many]

Additional Information:

68-82 Vette brake system information:

Power
Caliper piston dia: 1.875" F 1.375" R
M/Cyl dia 1.125"
Pedal Ratio 3.38:1

Manual
Caliper Piston Dia 1.875" F 1.375" R
M/Cyl Dia 1.00"
Pedal Ratio 5.40:1

Many master cylinders utilize the same mounting dimensions as the C3 Corvetter master. It is likely a person could find a master cylinder with a piston diameter closer to the C4 piston size that fits the Flat Our booster. A 1973 Camaro master cylinder for example is 15/16" (.93") diameter F and R.

[1project2many]

Additional information potentially useful for Hydroboost swaps (Hopefully to be edited for clarity)



Typical maximum pressure for Saginaw Type I pump: 850 - 1200 PSI.
Maximum pressure determined by flow valve length and flow valve spring.
Typically flows up to 20 gpm. Good info here (focused on increasing pressure).



Type II Saginaw / GM pump typical output pressure 850 - 1200 psi.
Lower flow than original Saginaw Pump, typically up to 15GPM.
Some additional info here.




Ford HB Mustang Pump specifications:
Power Steering Pump — CIII
Flow 9.8 liters/minute (2.6 gpm)
Fluid @ 74°-80° C (165°-175° F)
Engine at 1,500 rpm Pressure 1,034 kPa (150 psi)
Fluid @ 74°-80° C (165°-175° F)
Engine at 1,500 rpm Minimum capacity 4.7 liters/minute (1.25 gpm)
Fluid @ 74°-80° C (165°-175° F) Engine at idle Pressure at 5,171 kPa (750 psi)
Relief pressure 8,274-9,510 kPa
(1,200-1,380 psi)

Saginaw rack sensitivity is entirely dependent on flow. Altering pressure alters maximum level of assist available. How to make Hydroboost and Saginaw rack play nicely together? Typical complaint is that steering rack loses assist when applying HB brakes. Possibly this is why 3/4T and 1T GM trucks are supplied with Saginaw box instead of rack? Looking at numbers it appears the best method might be to use GM pump with an accumulator attached to the HB supply line to prevent rapid pressure drops. How much volume is enough? Manually adjustable flow control valves are available as well.






More info here:
https://www.hotrod.com/articles/ccrp...ering-secrets/

[Eagletucky]

Thanks to everyone that posted. Lots of good thoughts here.

I like to idea of the hydroboost, but the cost and looks kinda kill it for me. My Wilwood Master cylinder is the same size as a factory C4 unit (7/8"). The booster i just installed yesterday is a dual diaphragm 8" unit. the truck does stop better, but i still can lock up the brakes. I believe the factory booster for the c4 is a single diaphragm 9" unit. I would have assumed that the dual 8" would have provided more pressure.

I will continue looking. If anyone else has any had any success with c4 brakes, i am all ears!

[1project2many]

Originally Posted by Eagletucky

Thanks to everyone that posted. Lots of good thoughts here.

I like to idea of the hydroboost, but the cost and looks kinda kill it for me. My Wilwood Master cylinder is the same size as a factory C4 unit (7/8"). The booster i just installed yesterday is a dual diaphragm 8" unit. the truck does stop better, but i still can lock up the brakes. I believe the factory booster for the c4 is a single diaphragm 9" unit. I would have assumed that the dual 8" would have provided more pressure.

I will continue looking. If anyone else has any had any success with c4 brakes, i am all ears!

I would also expect the dual booster to help more but I think it's important to look at the pedal ratio as well. The pedal ratio is what converts pressure at the master cylinder into foot feel.

Could you clarify this please?

the truck does stop better, but i still can lock up the brakes.

What pads and rotors are you using? Sometimes the difference is very noticeable.
Also, which year calipers are you using?

[daveshilling]

Originally Posted by Eagletucky

I like to idea of the hydroboost, but the cost and looks kinda kill it for me.

If you mount it on the frame, you'll never see it...that looks better than any firewall brake setup, but I'm assuming that you've already gone firewall mount so moving to the frame would be ugly in a different way. Price-wise I think it's pretty similar.

If you're on the firewall already, just run a factory C4 setup as a baseline. That will be your "control" since in theory it should operate your C4 brakes perfectly. If you still don't like the brakes, then something else is up.

[mick53]

On my 53 3100 Wilwood recommended the 8" duel diaphragm booster. I have 12.88" disk, 6/4 piston Wilwood calipers. Master cyl is 1 1/8". I also have a MP vacuum pump due to my blower. I don't know what all that means I just thought I would throw it out there. This was custom designed by Wilwood over a few weeks and many phone calls at no charge. Then they sent me to Summit with part numbers to buy the parts because they said they were less expensive, $650 less for all of the major components so about 10%. I ask them why Summit was less money than buying direct and they said "It's not our thing and they sell a lot of brakes". Thank you for your time.

[mick53]

I'm glad I went with electric P/S.

[_Ogre]

not sure how you mean to run the hoses thru the cab
firewall pic shows how i mounted the remote reservoir
2nd pic you can see the reservoir to the right of the mc, the lines come out the back

Originally Posted by Eagletucky View Post
I like to idea of the hydroboost, but the cost and looks kinda kill it for me.

not sure what looks you mean about the looks, i like the clean firewall look myself
you can mount the vac booster under floor, but it has to be the small 7" dual diaphragm
i've heard mixed reviews on them, thus this ogre went full hydroboost

[daveshilling]

Originally Posted by _Ogre

not sure how you mean to run the hoses thru the cab
firewall pic shows how i mounted the remote reservoir
2nd pic you can see the reservoir to the right of the mc, the lines come out the back

Yes, I'm considering mounting in the cab, on the drivers side, where the factory jack mounts, and not on the lower firewall. Less hose, less crowding in the column/brake/exhaust area.

[_Ogre]

ah, sometimes you gotta draw a picture for me