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What do I need to convert my '67 drum brakes to disc
brakes?
First...read the
OLDSmobility.com's disc brake swap page.
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Here is what is different between a manual drum and power
disc-equipped vehicle: An Olds with power disc brakes would have different booster lines
and master cylinder (cylinder inside diameter, typically, would be larger). The PDB system
would use a front proportioning valve, either in line or as part of the distribution block
that would regulate brake line pressure. The front spindles and knuckle assembly is
different as are the front brake hoses (style and length). The rear brake wheel cylinders
are different (smaller).
You must get the front to rear brake line pressure proportioning correct or the first time
you nail the brakes hard the rears will lock up on you and cause the car to drift.
The front spindles might interchange but the Olds parts books show them a different part
number. The fittings on the ends of the lines are supposedly different so the disc brake
proportioning valve probably won't bolt up to your existing brake lines- (at least the
front ones, or so I have been told)--- adapters are supposedly possible to use, If you can
find the correct size (big IF) This was supposedly so the factory workers couldn't
accidentally bolt up the wrong brake lines to a disc car. This is just what i have heard,
haven't done it myself yet. The bore on all the master cylinders
I have found is THE SAME
as my drum MC, but the plunger inside is NOT the same, so you could technically put the
guts from a disc MC inside of a drum MC and it would work fine with the discs. New Master
cylinders are cheap enough where this would just be a waste of time, unless you plan to
convert a newer style dual bale MC to work with your discs. It IS possible. The older
style "fat" dual bale MC may in fact have a larger diameter bore. I have never
had the opportunity to disassemble one of those. |
When swapping disc brakes for your existing drums, any GM A-body through '72 will
bolt right on to your '67. Other suitable donors include the '70-'72 Monte Carlo or
Grand Prix, '67-'69 Firebird/Camaro, or '74 Omega/Nova/Apollo.
When you find an appropriate donor car, you'll need to get everything from the steering
knuckle (spindle) out, including steering knuckle, splash shields, rotor, calipers and
lines, master cylinder/proportioning valve, ALL the forward metal brake lines if they are
still usable, and if it's a Cutlass-type, the brake hose frame brackets. New rotors and
calipers are available but its nice to have the originals to give as a core deposit. Just
re-use your original steering arms.
NOTES
NOTE 1: I've been warned against using a Nova/Apollo proportioning
valve. I was told they are calibrated for a lighter car.
NOTE 2: A stock '67 drum setup has no proportioning valve, only a
distribution block. The '67-'70 disc brake setups used the same distribution block and a
separate proportioning valve mounted on a bracket under the master cylinder. The '71-up
disc brake setups used a combination valve which had the proportioning valve integrated
into the distribution block. You must install the proportioning valve behind the inline
electrical switch that signals the dash light to come on or it will stay on when the
brakes are applied. It must be attached to the rear brake line after it leaves this block.
You can make your splice inside the frame on the drivers side where the rear brake line is
located. There is plenty of room there and hard lines can be routed easily enough.
NOTE 3: Anytime you're doing a swap of this nature, it's best to
replace the brake hoses. The reason I suggested getting the hoses from the donor car was
for length verification. After installation, make sure the brake hoses aren't pulled tight
when the wheels are turned. A friend used brake components from a Chevelle, and noticed
after installation that the Chevelle hoses were too short. However, it was a simple task
to go to the parts store and find the longer hoses with the correct ends. A good upgrade
would be to install braided steel lines from the hard lines to the calipers.
NOTE 4: If you're planning to convert to a stock 10" rotor setup,
the 14" SSIIs will fit fine - they came that way from the factory. The dual-piston
calipers were used on '67-'68 cars only and are somewhat hard to find (read: $$$). The
single piston system used on '69-'72 cars is much more common and easy to find. It is
completely interchangeable with the earlier system (at the spindle level).
In my opinion, the later system is better for two reasons. First, the calipers slide
side-to-side, which allows for slight warpage in the rotor - the four-piston calipers are
hard mounted to the spindles and any rotor wobble causes the pistons to be pushed back
into the caliper, which increases pedal travel upon initial application. This is not what
you want in a panic stop! Second, the four-piston design uses smooth bores in the caliper
and pistons with grooves for the seal rings - just like the pistons in an engine.
Unfortunately, the cast iron caliper bores are susceptible to rust and pitting, which is
why companies like White Post make a tidy profit lining these calipers with stainless
sleeves. The single-piston calipers reverse this by having the seal
ring set into a groove in the bore. The sliding surface is the OD of the piston, not the
ID of the bore. To further improve this, the pistons are chromed, which minimizes their
likelihood of rusting. More importantly, it's pretty cheap to replace the piston verses
having the caliper sleeved.
QUESTION THIS:
A lock-up problem can be attributed to
a mal-adjusted proportion valve. Did you remove and relieve the restrictor valve in the
master cylinder on the front brake side? I pulled mine out of the master cylinder with a
makeshift slide hammer and drill it out so flow to the front brakes was not restricted.
NOTE 5: A popular upgrade is to use stainless steel lines. If you do
so, you really have to tighten (read over-tighten here) just to get the ends to
seal properly because the stainless is so hard.
NOTE 6: Check out www.p-s-t.com for
another option. They sell a drum-to-disc conversion kit with 2" drop spindles.
NOTE 7: From what I understand, power discs also require a larger
diameter hard line. The connectors on the end of the lines should have been different as
well. I was told that this was a obvious indicator to the factory workers that the correct
lines were installed to the proper type brakes. You can buy the conversion line set that
goes from the master cylinder to the front discs. These lines connect up to the
proportioning valve and to each brake area.
NOTE 8: If the components you're purchasing are at a local swap meet,
and you want to verify the year of the parts, look at the steering knuckle.
'72-and-earlier had a two-piece unit (the steering arm bolts onto the knuckle), while the
'73 and later one-piece units had the steering arm cast into the knuckle. Make sure the
master cylinder was from a disc-brake-equipped vehicle. They are different.
NOTE 9: Be sure to bench-bleed the master cylinder before installing it.
As for bleeding the brakes alone in your garage, use a one-way inline valve on the bleeder
hose. I put the bleeder hose in a jar containing some brake fluid so there is less chance
I can draw air back into the system too. Then I crack the bleeder just a little. I then
bleed them myself starting from the point farthest away from the master cylinder and
working towards the nearest (right rear, left rear, right front, left front.) Never had a
problem. Just remember to add fluid during the bleeding. You'd hate having to start over
because you sucked it dry in the middle of the bleeding process, re-introducing air into
the system.
What
aluminum brake drums will fit my '67s rearend?
9 1/2" x 2" aluminum rear drums were used on S-10 pickups and G-bodies. These
will fit your '67. As for usefulness, anything that reduces
unsprung weight will be beneficial for handling.
How about converting to 12" disc units?
Are things any different?
The spindles in question should be for a '77-'90 GM B- or C-body with 12" disc
brakes -- that being any C-body, any station wagon, or anything with a police package.
'91-'96 will also work, but the parts will cost more because they are made for ABS. All
those cars use different ball-joints than '64-'72 A-bodies, so you have to buy ones
specifically for the swap. These spindles are also taller than the originals, so you may
have problems setting camber without using Hotchkiss or other upper control arms
specifically made for this conversion. Global West kits have the correctly turned-down
lower ball joint and tie rod ends.
Secondly, you'll need Camaro 1LE rotors with a 4.75" bolt circle, since the full-size
cars have 1/2" studs on a 5" bolt circle. The 1LE rotors cost $90 each at the
part store. They come with metric studs and are on the desired 5 X 4-3/4" bolt
pattern. You can pop out the studs and put in 7/16 studs but you'll have to widen out the
holes. (Or if you prefer, GTRotors has CNC milled and drilled 1LE steel rotors for a
reasonable price.)
Lastly, the 12" brakes won't fit 14" wheels, and they won't fit some 15"
wheels (definitely not 15" SSIII wheels, since they have the same centers as the
14" version).
While it is possible to put the '73-'77 spindles on the '64-'72 cars, this is NOT a
bolt-in swap. The ball joint size and taper was changed, which means that you must use the
'73-up ball joints. This will require machining the body of the lower ball joints to fit
into the early control arms. The '73-'77 spindles are also taller than the early spindles,
which will require either excessive shims on the upper control arm or the custom
fabricated arms sold by Hotchkis or Global West. Finally, the '73-'77 spindles will also
require the later outer tie rod ends, again to match the different taper.
The bottom line is that after all this work, you will still only end up with the same size
discs as if you had used the '67-'72 brakes. It would make more sense to get your hands on
a set of B-body spindles with the 12" rotors. The work to install them is the same,
but the brakes are bigger.
How do I remove and install the
rear suspension bushings?
When you remove the upper control arms you'll notice that the
upper-control-arm-to-differential bushing is pressed into an ear ring which is part of the
differential. You can remove these bushings easily enough by cutting it out with a torch.
However, speaking personally, having fire in that close a proximity to the gas tank always
freaks me out, and since there's only a few additional attaching points left holding the
differential in, it's probably better for peace of mind to simply drop it out completely
so you'll have access to everything and can comfortably work on it.
So, how the heck does Joe Average press in a new one? Put the bushing in the freezer
for a while until it's good and frozen. Then heat the hole in the rear up with the torch.
You should be able to tap it right in. Don't worry about banging on those ears on the
housing...they're tough.
Another option is to use a bushing
installation kit, but it can be a pain. The way GM
intended for it to be done was to press it in or out using a pushing socket that is same
diameter of bushing sleeve, and have a receiving cup, larger than sleeve, on the other
end. You can recreate this principle with a bushing installer that has the cups and a
c-clamp that is driven by a socket wrench. It moves slow but eliminates all risks to the
differential ear rings. Heating will work with frozen bushings, and even with the
push-pull method described by service manual above, still freeze the bushing for easier
install, 24hr. Remember that heating any metal too hot will change its grain structure and
material properties, potentially weakening it. Also, Snap-On and Mac Tools (as well as
Harbor Freight) sell these bushing installers, $50-70.
What do I need to properly lower my 442?
Hotchkis makes a spring kit that will drop the car 1-2"" and make it handle
better for about $250. The car will have a very nice stance and corner a good bit better.
NOTE: Never ever heat springs with a torch! This will destroy the
temper in the springs and WILL cause them to fail.
What causes my car's body
to lean?
Body lean is a common problem with Cutlass/442 owners. It seems to be almost always
leaning to the drivers side, even after rebuilding the front end with bushings, springs,
shocks, etc. When tracking down the culprit on your car those are always the most obvious
things to look at. FYI, there is no difference between left- and right-side springs.
When replacing the front and/or rear bushings, do NOT tighten them up with the car up
on jackstands. They MUST be tightened with the vehicle sitting on level ground. Otherwise,
the bushings will be pre-loaded and could cause a lean to one side or the other. Bolt on
the tire/wheel combination you plan on using, place some weights corresponding to the
approximate weight of the driver in the driver's seat and floorboard, bounce the car up
and down a time or two to level it out, and then tighten the bushing bolts to the correct
torque specs.
It could be the body bushings or the body mounts themselves. The car should have 7
bushings per side, including the radiator supports.
The frame should be checked for straightness as well. The only way to know is to put it
on a frame machine. You cannot "eyeball" the dimensions. If you have the frame
out of the car it is a joy to straighten. A guy can get at all the measuring points and
get a true datum line. Having the control arms is an asset because the ball joint
measurements are also very important. The non-convert frame has very little stiffness and
relies heavily on the body for its strength. If you get a person on each end and twist you
will see what I mean, so the body must be "square” as well. You can also measure
a datum from the mount points on the body.
When measuring your car you must have a level floor. Also make sure the body is square
on the frame. Being low on one side is not as bad as low on opposite corners. That almost
invariably points to damage. When checking your heights, scales are almost imperative.
With them you can determine if your low corner is "low and heavy" or "low
and light”. If the corner is low and heavy it is being pushed down by the opposite
corner of the car and is not being caused by a dead spring or mounting. If it is low and
light, the car is falling to that corner and a dead spring or mounting area could be at
fault. Think of it as a short table leg. The opposite corner can cause the problem. Bound
up sway bars or bushings can cause trouble, but as one poster stated, these cars are
almost always leaning left. You should do your checking with the bushings loose and the
bars disconnected. I have also seen bent, twisted sway bars. Many guys buy bars from
wrecks and introduce a problem that way. If you can get the car on a scale set when
measuring you can really get an idea of what is going on. You will quickly see that the
left side does weigh more and with the Olds soft spring rates it will take very little to
make it lean. Try having some one watch the front while you push one or the other rear
corner up or down, doesn't take much does it?? If you are on scales you can trim or shim
springs if necessary to level if the chassis and frame are check out. By having the wheel
weights you can do this with out creating a dangerous handling situation. In fact the car
will likely handle better. But you need to have the weights to know if you add to one
corner or remove from the opposite.
Want to really feel bad? Have some one sit in your drivers seat when you look.
It’s even worse than you thought. In a perfect world you want the car level side to
side with equal side-to-side corner weights with the car loaded as driven. Unless you are
going to physically shift weight in the car to make up for driver and components (battery
in the right rear and stuff like that), the next best thing is nearly level with somewhat
equal nose weights. In my opinion on the street getting the nose weight right is the most
important due to braking and handling. Drag racers (which I am not) place more importance
on rear weight balance, and rightly so. Sorry to ramble on, the above are some of the
things I have seen but it is at times tough to figure some of these out hands on let alone
by the net. If nothing else they will give some insight into the situation
Many Cutlass/442 owners 'fix' the problem with airbags. The owner of a '68 reported the
assembly manual shows a spacer for the left side only, but even after installing it, there
was still a lean. He got a set of airbags for the rear springs, and was told by the vendor
that it would be OK to put a spacer on top and bottom of the bag so once inflated gives a
little lift too. Fixed the problem .
Incidentally, air shocks are not the way to correct this problem. The shock mounts are
not made to take the weight that should be in the spring housing. Besides, if you have the
air shocks connected with separate lines and one blows out while your driving, you can
lose control. Try the airbags!
Here's another thought: In an Olds-related messageboards there was a discussion about
the rear sway bar. Overtightening the rear sway bar, or mounting it without the necessary
side spacers would also preload the chassis, and could conceivably tweak the rear chassis
area. From what I understand, early racers found that by putting a rear sway bar on the
Cutlass lower control arms that were NOT boxed, they could overtighten the attaching
bolts, which would preload the rear chassis in such a way as to act as a cheap traction
device. They reported it did seem to help traction a bit, but made the car really
squirrelly to drive. So...you might want to eliminate those two ideas as culprits.
Collapsed spring pockets in the front cross member are a distinct possibility, but this
usually happens from an impact and not age.
How do I convert from DOT3 brake fluid to
silicone fluid?
First of all, any non-silicone brake fluid is hygroscopic. That means that these fluids
will absorb moisture over time. That is why silicone is good for a car that sits more than
it is driven. Silicone brake fluid, contrary to what you might read, does absorb water to
an extent -- but rather than mixing with the water it absorbs, it tends to surround the
water, sort of like a drop of water in cooking oil...the water can't touch any thing
metal.
DOT3 and silicone fluids don't mix well. However, I did exactly what you want to do. I
probably pumped about 2 quarts of silicone fluid thru the system, and did not have any
problems over the next 8 years that I owned the car. Obviously, the best approach is to
start with new and dry parts. I think if you purge the system thoroughly, however, you will
be OK....
Due to the design of the proportioning valve in a 1969 GM disc brake design, stay away
from silicone fluid in one of these-it will be impossible to bleed the system. The valve
sits in a position to trap air bubbles, and the junctions will actually cause bubbles with
the higher viscosity silicone fluid. Simply install DOT 3 or 4 fluid, and flush it every
two years or so. This is much cheaper, by the way. Its also far better to use the vacuum
method to change fluid in a 1969 GM disc setup -- they were notoriously hard to bleed in
their day.
I put a new brake power booster in my Cutlass. When I
hit the brakes, the brake pedal goes to the floor and stays. The brakes work but the pedal
will not return.
This sounds like you've got the wrong master cylinder/booster combination. Oldsmobile
used both Moraine and Bendix boosters and master cylinders, and the master cylinder for
one type doesn't work with a booster for the other type. The pushrod recess in the master
cylinder is deeper in one type, and if you put it on a short-pushrod booster the pushrod
has to travel a short distance before it will actuate the brakes and then won't return.
(The master cylinder return spring will only push it back to the point where the cylinder
plunger is in the fully retracted position, which might not be giving you the proper pedal
height.) Another variation to this problem happens if the shallow-recess master cylinder
is put on a long-rod booster. This will lock the brakes before you've pushed the pedal
more than an inch or so and pedal will be very hard. These problems are more often seen on
full-size cars, but it can still happen on A-bodies. The bottom line: verify that the new
booster or master cylinder you purchase is the same style as the original version. If you
purchase a booster and master cylinder together as a unit they will be correct either
way...otherwise, you need to check before making the purchase.
I want to convert to a
quick-ratio steering box. What are my options?
The mid 70's
Firebirds and T/A's have 15:1 or the WS6 'Birds have 14:1 steering boxes. The
Monte Carlo SS has 12:1 as do the Hurst
Olds. I installed a '83 Monte manual steering box in
to my '67 F-85. You will need the coupler
clamp from the Monte and the pitman arm from the
'67.
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