The car
has a an under floorboard brake system with a seven
inch dual diaphragm vacuum brake booster, a 1 inch bore dual port master
cylinder, 1988 Camaro front disc brakes, 1978 lincoln Versailles rear disc
brakes and 30 inch diameter rear tires. The car occasionally tows a 1300 pound
trailer. The braking power of this configuration was unsatisfactory.
After
consideration of several options, conversion to hydraulic brake boost
(hydra-boost/ hydroboost/HB) was selected.
I went
on-line to do research, then to ebay and ended up contacting seller “sterlingworth16”.
The seller turned out to be Elliott Sydnam of Custom Hydroboost. I explained to Elliott my brake issue and how
space was a limiting factor for this retrofit. To my pleasant surprise Elliott
was a wealth of knowledge and was eager to help me select the appropriate HB
for my car. I discovered Custom Hydroboost could set me up with just about any
adaptor you could imagine to install HB on my vehicle. Custom Hydroboost makes
a wide variety of adaptors, tools and booster related items as well as
maintains a variety of Hydroboost (HB) units in stock. Check out his web site
(Texashydroboost.com) it is full of helpful information. After a couple of question
and answer sessions with Elliott he sent me a unit specifically configured for
my application and a packet of installation information.
Elliott
sent me a new Bendix unit commonly used on the 1984-87 GM Military CUCV
(Commercial Utility Cargo Vehicle) M1008. The trucks were all rated as 1-1/4
ton. It turned out this new HB would only be ¾ of an inch longer than my vacuum
booster.
I next
roughed out a project schedule
1.
Prep car
2.
Vacuum test and Check Valve inspection
3.
Baseline brake pressure
4.
Fit check and retrofit the booster assembly
5.
Remove front fenders, inner fender panels, hood and radiator nacelle
6.
Retrofit power steering pump
7.
Plumb hydraulic lines
8.
Bleed system
9.
Reassemble front fenders, inner fender panels, hood and radiator
nacelle
10. Re-baseline
brake pressure
11. Road
test and adjust proportioning valve
1. Preparation
2. Vacuum Test
I ran
the engine at idle. Engine vacuum at the manifold read 18 inches. I tested the
vacuum booster check valve and found it was operational and not leaking.
3. Baseline brake pressure
I
performed a baseline brake fluid pressure test at front and rear calipers using
a brake pressure gauge. I could not come up with a way to measure the force
being applied to the brake pedal for consistent repeatability of the test so I
applied what I felt was maximum force seated in normal driving position. I then ran a series of tests to establish a
norm. Eight out of the ten readings were within 100 pounds and I recorded that
value.
Front
caliper, no boost (engine off): ~ 500 PSI, with vacuum boost at engine idle: ~ 1000
PSI
Rear caliper,
no boost: ~ 500 PSI, with vacuum boost engine at idle: 800 PSI
4. Fit check and retrofit the booster assembly
I removed
the adjustable proportioning valve which is mounted to the frame just below the
master cylinder (MC). I was then able to remove the vacuum booster and MC assembly
from under the car. I would reuse my 1 inch bore MC so I reattached it to the
new HB unit and attempted to reinstall the assembly back into the car. When I
tried to install the assembly in the upright position, the HB accumulator hit
the inside frame rail and one of the frame crossmembers interfered with the
reservoir inlet fitting of the secondary MC port. I rotated the assembly 90⁰ counter clockwise
and everything cleared. I tried the two other positions but this orientation
appeared to be the best. The sideways orientation of the MC inlet ports seemed
odd at first but with a remote reservoir configuration the MC does not care
what position it is in as long as it gets fluid. Modifying the frame
crossmember was not an option. I was not concerned about removing air from the
MC as long as I pressure bled the MC through the inlet port hoses at the remote
reservoir located on the firewall. I then bolted the assembly in place to fit
check the remaining components. I discovered the reservoir hoses for the MC
were now too short, the clevis on the input rod was too long because the jamb
nut could not be installed on the input rod, and there would be very tight
plumbing space issues (that was expected). I also discovered the bottom MC mounting
stud obstructed the proportioning valve knob when I installed the proportioning
valve back onto the frame. It was also obvious I would need to fabricate new MC
plumbing due to the added length of the HB moving the MC rearward ¾ of an inch and
the new sideways orientation of the MC.
The
short reservoir hose was an easy fix. I connected the longest hose to the
primary MC port and reused the ends off of the shorter hose to make a new
longer hose for the secondary port. The input rod clevis was too long and I was
not able to fit the jamb nut Elliott sent with the unit. There was about one
inch of thread in the clevis body so I decided to shorten it by ½”. This would
allow proper pedal adjustment and the incorporation of the jamb nut. In order
for the jamb nut to seat properly against the clevis body I need to cut the
clevis off flat and square. I found a
three inch long bolt with 3/8-24 treads and cut the head off. I chucked it in
my drill press and threaded the clevis on from the pin side. I turned the drill
press on and cut ½ of an inch off using a die grinder fitted with an abrasive
cut off wheel.
I
removed the bottom MC mounting stud from the HB after much time and effort. I
could not get the metric stud to back out. I finally sent Elliott an email
asking for advice. He replied right away with the solution…They seat with left
hand threads!...Duh! After I removed the stud I replaced it with a 3/8-24 grade
eight bolt, two washers and a fiber lock nut. I inserted the bolt from the rear
and fastened the nut from the front. This configuration rendered the space
necessary to allow operation of the knob on the proportioning valve again.
I then fabricated
a new brake line to run from the front brakes residual valve to the primary
port of the MC and a new line from the proportioning valve (rear brakes) to the
secondary port of the MC. Note: Residual valves are used when the master
cylinders are mounted below the level of the calipers. This keeps the brake
fluid from draining back to the master cylinders so you don't have excessive
pedal travel and caliper restriction. They are available in two sizes, 2 lb.
and 10 lb. The 2 lb. is used for disc brakes and 10 lb. valves are used in drum
brake setups. The higher drum brake pressure valve is necessary to compensate
for return spring tension.
I use 7
gauge galvanized wire to mock-up my bends and then I follow my mock-up when
bending the tubing for an accurate fit.
5. Remove front fenders, inner
fender panels, hood and radiator nacelle
In order
to access and remove the power steering pump it was necessary to remove the
body work from the front of the car. The length of the engine and transmission
package left little room between the radiator and engine when I built this car.
I originally
constructed the car with a General Motors Type III power steering pump to
accommodate the low flow and pressure requirements of Ford Thunderbird rack and
pinion steering setup. The Type III pump was fitted with a custom serpentine
pulley to make the pump compatible with the OEM Dodge serpentine pulley system.
I now converted back to the original OEM Dodge pump which has a larger
reservoir, three point mounting instead of the GM two point mounting and a
non-custom OEM pulley that is available at most parts stores. I wanted to keep
as many parts as possible OEM because I have found from past experience using
aftermarket parts create problems when future repairs or especially repairs on
the road are necessary. The Dodge pump was sent out for a rebuild and to have
the flow adjusted to two gallons per minute for the Ford Thunderbird steering
and the pressure lowered from the original Dodge specs of 1615 PSI to 1450 PSI for
the new Bendix HB. The new HB unit is rated for 1500 PSI but it has no relief valve
so I opted to run a conservative pump pressure to avoid pressure leaks or
damage to the system.
My under
floor brake system is configured so the master cylinder and booster face the
rear of the car instead of the front of the car. In vehicles where the master
cylinder and booster are mounted to the firewall, the master cylinder and
booster generally face the front of the vehicle. This rear facing configuration
created some plumbing challenges due to the limited space within the frame
rails, crossmember and floorboard.
8. Plumbing
The
Bendix HB unit was designed to use 5/16 -16mm x 1.5 and 3/8 -18mm x 1.5 O-ring
or “Bump Tube” style hose ends. The 3/8 -18mm port is the pressure supply inlet
from the power steering pump, the 5/16 -16mm port is the pressure supply outlet
which flows fluid to the power steering gear box or rack pressure supply inlet.
There is also a 5/16 -24 thread x 3/8 hose barb fitting which serves as the
power chamber vent line. The power chamber vent line returns fluid to the power
steering pump reservoir when the brake pedal is released after each application.
These hoses
with “Bump Tube” ends work well in OEM applications but where custom
installations are needed these ends are not friendly to fabrication. I was not
able to find a tool to make bump tubes and I was not able to find bump tube
hose ends sold separately other than a few air conditioning pieces and they
were relatively expensive compared to other options. I assume one option would
be to buy wrecking yard hoses and cut the ends off and do flare and unions or
weld them to your plumbing but I opted out of that approach. I finally decided
to use AN or JIC style fittings since I had used these fittings in other
systems on the car and many adaptor and fitting options were available on the
internet and through local suppliers. The following examples are some other
plumbing options I found:
Flare
inserts. These can be used to convert a typical bump-tube style ports to be used
with flare style fitting. Hydratech http://www.hydratechbraking.com sells a
set (part number HBS9106). Set includes one 5/16 Tube Seat and one 3/8 Tube
seat
Flare
Inserts can also be found at Autozone and air conditioning fitting suppliers
Another
option is -6AN to bump- tube adaptor fittings. Sweet Performance Products, Inc.
http://www.sweetperformance.com
714-223-9322 makes a hydroboost fitting kit (Product Code: HYDD246). The kit
includes, one -6 to M16-1.5 bump-tube fitting, one -6 to M18-1.5 bump-tube
fitting and one -6 to 5/16-24 fitting.
Other
options are high pressure hose kits. I found several companies who make
hydroboost hose kits.
Yet
another option is steel tubing. Since all of the tubing on my car is stainless
steel I did not investigate mild steel tubing pressure ratings. I would not
hesitate to use mild steel tubing on another project as long as I verified the
pressure ratings first. The tubing I looked at was 304/304L Stainless Steel
Tubing - 3/8" OD x 25' .020 wall
In order
to use tubing with AN or JIC fittings you must first flare the end of the
tubing to 37⁰ and use a sleeve and tube nut.
Common 45⁰
flaring and double flaring tools are made for Standard brake and fuel lines will not work with AN or JIC
fittings. AN and JIC fitting ends are machined to 37⁰ and therefore require a matching 37⁰ flare on the joining tube.
I
decided on the stainless steel tubing option with the bump-tube to AN adaptors.
I did consider hoses but tight turns were a possible kink or flow issue for my
particular installation. I also was concerned about long runs of hose and the
diameter of the hose passing through the available narrow routing passages to
the front of the car. I purchased the tubing off of ebay and the adaptors from
Sweet Performance Products.
I also need a low profile piston vent fitting.
I ended up fabricating an elbow from brass fittings I had on hand. I started
with a 1/8 pipe thread (NPT) to 1/8 tube compression fitting. The compression
cap threads were 5/16 -24 which would thread into the HB body and the other end
was male 1/8 NPT. I then took a 3/8 hose barb elbow fitting with 1/8 male NPT threads
and cut the male NPT threads off. I drilled the hose barb body with a 21/64 bit
and taped the hole to 1/8-27 NPT. I then examined the bore in the hose barb
that came with the HB and discovered it had a 1/8 inch bore. The compression
fitting I was using for the base of my elbow had a smaller bore so I drilled it
out to 1/8 inch to match the original HB fitting. I wanted to assure there
would be no flow issues. I assembled the elbow on the HB unit mounted in the
car so I could tighten the pipe threads to a point where the hose barb was
pointing in the direction I wanted the return plumbing to go. I would later add
an O ring upon final assembly to assure a proper seal at the HB body.
It was
now time to fabricate the HB hydraulic lines. I cut a five foot piece of 7
gauge mock-up wire and began laying out the pressure supply line. I then bent
the tubing to shape, flared the HB end and connected it to the banjo fitting on
the HB. I then repeated the process for the pressure return and the power
chamber vent line. Due to the tight clearances above and on the right of the HB
I ran all of the tubes rearward then made 180⁰ bends to go back forward close
to the right side of the HB body and through an existing slot in the HB/brake
pedal mounting bracket.
I left
them long and devised a way to bundle and support them to the frame.
I had
connecting points for the power steering pump and the steering rack but I did
not have a point for the reservoir return. All of the installation instructions
I found recommended a reservoir with two independent return inlets, one for the
steering and one for the HB. My
reservoir only has a single 5/8 inch hose barb return. The second choice was to
use a Tee fitting. Many articles I read cautioned against Tee fittings due to
possible pulsing or other anomalies when applying brakes and turning at the
same time. A third option would be a Y
fitting. Several manufactures make Y fittings but they were not available in a
configuration I could easily use. Because my OEM Dodge reservoir has a 5/8 inch return
inlet, I was confident it could handle the flow of two 3/8 return lines so I
opted to make my own full flow Y fitting. I salvaged a brass heater core inlet
tube and two 3/8 steel tube bends from a scrap power steering hose. I cut the two
3/8 steel tubes to length and inserted needle nose Vise-Grips inside the tube
openings and clamped them together. I then held them in place under the
reservoir return inlet and adjusted the tubes until they were pointing in the
direction I wanted. I took them to the bench and tack welded them together. I
then cut the brass heater core tube to length and stretched the end opposite
the barb to an oval shape and brazed the two 3/8 steel tubes to it. I cut a two
inch piece of hose and joined the Y fitting to the reservoir inlet.
I then
began connecting my HB tubing to the respective points. The diagram below
illustrates how the hydraulic circuit is connected.
The
Thunderbird rack was also designed to use bump-tube style fittings. My steering
rack was converted to bump-tube to -6 AN male adapters during the original
construction of the car. I needed to install a 16mm to -6 AN adapter on the new
power steering pump but the shoulder on the OEM outlet fitting was too deep and
it would not allow the O ring on the adapter to seat. I removed the OEM fitting
from the pump and chucked it in my drill press, turned it on and cut ¼ inch off
using a die grinder fitted with an abrasive cut off wheel. I cleaned and
reinstalled the fitting into the pump and installed the AN adapter fitting on
to it. I then took measurements for the two pressure hoses. Each would need to
be fitted with a 90⁰ full flow fitting on one end and a straight fitting on the
other. I discovered it was less
expensive to use crimp on fittings rather than the field serviceable type so I
measured and had the two Teflon/steel braided high pressure hoses made at a
local industrial supply center. The low pressure return hoses I fabricated from
3/8 I.D. oil resistant hose typically used with transmission coolers. I flared
the pressure supply and pressure return tubes coming from the HB connected them
to the pump and steering rack using -6 AN unions. On the steering rack low
pressure return line and the HB vent line I used spring clamps to secure the
hoses to the tube and fittings.
I ran
hoses to the engine and rack to provide movement and vibration protection.
Notice the loop on return hose rather than short straight run.
I then
snugged the banjo fittings on the HB, disconnected the tubes and removed the HB
from the car. On the bench I marked the HB banjo fittings so I could reinstall
them in the same position. I removed the banjo bolts and applied blue Loctite
to the threads and reinstalled them. I
torqued the 16mm banjo bolt 40 foot pounds and the 18mm bolt to 45 foot pounds.
The brass piston vent fitting I gingerly torqued to 10 foot pounds.
installed the dust
cover over the input rod, added the jamb nut and clevis then reinstalled the HB
and MC back into the car for final assembly. I connected and adjusted the
clevis for proper pedal height, and connected the brake light switch spring to
the pedal arm. I reconnected tightened all of the hydraulic and brake lines and
torque the MC banjo bolts to 25 foot pounds. I pressure bleed the brake lines
and refilled the MC remote reservoir.
To bleed
and prime the HB and steering system I disengaged the serpentine belt from the
power steering pump and filled the pump reservoir with fluid. I then turned the
steering wheel from lock to lock four or five times. I then used a low speed
drill motor fitted with a 5/16 ball hex inserted in the pump shaft to spin the
power steering pump clock wise. As I spun the pump I watched the fluid in the
reservoir as it bubbled at first then turned fizzy for a few seconds and then
ran clear after about one minute of priming. I then turned the steering wheel
lock to lock a couple more times and spun the pump with the drill again, no
air…good!
I
reassembled the front end of the car and ran the engine. I checked all fitting
joints for leaks, cycled the steering several times and applied the brakes and
looked for leaks again, all was good. I shut off the engine and checked the
steering and brake fluid levels.
Note: in
some cases where leaking joints are a problem you can use copper inserts that
go between the fitting and the tube flare called Flare Savers or Flare Inserts.
They act as a gasket and will usually stop leaks.
3/8"
Flare Savers or -6 AN Flare Insert
Next I
installed the brake pressure gauge on the front caliper and began my before and
after comparison test. The front caliper with Hydroboost and engine at idel: ~
2400 PSI
Rear
caliper with Hydroboost and engine at idel: 1600 PSI
Front
caliper pressure before Hydroboost was 1000 PSI. Pressure with Hydroboost is
now 2400 PSI; yield 140% increase. Rear caliper before Hydroboost was 800 PSI. Pressure
with Hydroboost is now 1600 PSI; yield 100% increase. Note the adjustable
proportioning valve setting was not changed between the before and after tests to
assure consistency. Changing the proportioning valve will shift more pressure
to the rear if needed when the car is road tested for braking balance. It should also be noted that when the engine is off idle the pressure will increase.
I
finished assembly of the car prepared for the road test. Road
test achieved four wheel lockup balance with the proportioning valve set at one
turn open. The new HB system has phenomenal braking force with the eight inch
wide tires in front and eleven inch wide tires in rear. The pedal feel and
control is very good, not under responsive or over sensitive.
I highly
recommend Hydroboost systems to people who want or need higher performing brake
systems on their vehicles.
