[Keith Seymore]

Subscribing (so I can find this when I need it).

Just lost the brakes on the GP last night (single system). Made it home safely by downshifting the trans and with what little brakes I had left, but getting the car in the garage was a challenge!!

K

[Keith Seymore]

Some of you know that I was a brake development engineer for GM light truck at the Desert Proving Ground in the early 1990's timeframe. My (professional) experience is therefore limited to dual systems but hopefully it is still ok for me to make some general observations:

a) Not to put words in mkoser's mouth but it seemed implied to me the thread was to discuss drum/drum systems. References to disc/drum systems tended to confound the issue and probably should have been avoided.

b) References to the master cylinder port location should be made from the perspective of vehicle position. That is, the front port is the one closest to the front bumper; the rear port is the one closest to the rear bumper. Any other frame of reference causes additional confusion.

c) In my development experience, even within modern dual systems, there were some that were front to front and some that were front to rear, depending on other considerations like hood clearance and relative reservoir size based on vehicle platform* In those cases it was obvious what the intention was, since the large reservoir would be for the front disc system. My point is that I wouldn't be surprised if early cast iron dual master cylinders had similar variation and it would be ideal if the part itself could tell us which way it was to be hooked up, similar to my aluminum master/plastic reservoir analogy. Since we are specifically discussing a '69 Bonneville m/c I wonder if the '69 chassis manual would provide any insights...

d) I have the brake system release charts for all LD pickups, starting in 1969. I'll take a look and see if they reference which port feeds which brake system (front to front vs front to rear).

e) I believe this thread was an excellent resource and am glad it is still available as a reference.

K

*example - the old M/L Astro/Safari mini van. The sharp hood angle cause the rear reservoir (located toward the front of the vehicle) to be miniscule in height. I tried one of these master cylinders on my Chevelle and, while it worked well for pedal feel/effort/travel, the angle of the installation meant that I had to jack the rear of the car up in order to put brake fluid in the rear system or to bleed the brakes.

[Scarebird]

Originally Posted by Keith Seymore

Some of you know that I was a brake development engineer for GM light truck at the Desert Proving Ground in the early 1990's timeframe. My (professional) experience is therefore limited to dual systems but hopefully it is still ok for me to make some general observations:

a) Not to put words in mkoser's mouth but it seemed implied to me the thread was to discuss drum/drum systems. References to disc/drum systems tended to confound the issue and probably should have been avoided.

b) References to the master cylinder port location should be made from the perspective of vehicle position. That is, the front port is the one closest to the front bumper; the rear port is the one closest to the rear bumper. Any other frame of reference causes additional confusion.

c) In my development experience, even within modern dual systems, there were some that were front to front and some that were front to rear, depending on other considerations like hood clearance and relative reservoir size based on vehicle platform* In those cases it was obvious what the intention was, since the large reservoir would be for the front disc system. My point is that I wouldn't be surprised if early cast iron dual master cylinders had similar variation and it would be ideal if the part itself could tell us which way it was to be hooked up, similar to my aluminum master/plastic reservoir analogy. Since we are specifically discussing a '69 Bonneville m/c I wonder if the '69 chassis manual would provide any insights...

d) I have the brake system release charts for all LD pickups, starting in 1969. I'll take a look and see if they reference which port feeds which brake system (front to front vs front to rear).

e) I believe this thread was an excellent resource and am glad it is still available as a reference.

K

*example - the old M/L Astro/Safari mini van. The sharp hood angle cause the rear reservoir (located toward the front of the vehicle) to be miniscule in height. I tried one of these master cylinders on my Chevelle and, while it worked well for pedal feel/effort/travel, the angle of the installation meant that I had to jack the rear of the car up in order to put brake fluid in the rear system or to bleed the brakes.

You may be able to simply switch reservoirs, from say a 81-87 G body.

[Keith Seymore]

Originally Posted by Keith Seymore

d) I have the brake system release charts for all LD pickups, starting in 1969. I'll take a look and see if they reference which port feeds which brake system (front to front vs front to rear).

Not particularly helpful but I thought it was cool to look at the old document (from back when everything was done by hand).

K

[64catalina]

On my 64 cat I believe the original pushrod was attached with a collar and pin w/clip.
New one had threaded rod and collar.

I have a question with all due respect to everyone here.
I have done the conversion on my car.
I am curious, why would you collect all the parts and pieces versus an established kit?
Not trying to stir up stuff just curious.
for me it was knowing I had what would work so I could be back on the road asap...

There is no good luck, its just what you make out of what you got...

[Keith Seymore]

Is there an established kit?

I have to stay drum/drum because I'm keeping the 8 lug aluminum wheels.

K

[64catalina]

I looked around a lot and master power brakes was the only one I found that would guarantee fit. disc upfront original drum in back.
uses calipers etc from a late 70'early 80's chevy all new parts with power $900 give or take
Came with everything but the ability to bend a really tight brake line..

[Keith Seymore]

Any input on why I'm crashed hard into the wheel apron?

It looks to me like I need ports on the inboard side of the master cylinder.

K

[Jeffs64Cat]

Used everything the Op did. Had to persuade the fender to give a little but in the end it saw it my way. I hooked the front to the front and the rear to the rear. No testing yet as still rebuilding the Cat.

Thanks to the Op for the write up!!!

[RAM YAK II]

I have a 62Cat that I put Scarebirds front disc conversion on. My lines were hard into the inner fender too. My son found a Corvette MC with the proper lines, prop. valve and provisions to mount the prop. valve under the MC. That eliminated the problem. I'll have to dig the info out and pass it on. If I remember right it wasn't very expensive.

[WQ59B]

RE my post 3-posts back, I have a couple of issues ~

1. the closeness of the inner fender and the adapters required on my MC to connect the lines to (which then moved the lines farther outboard), forced me to loop the brake lines at the MC UP, and I think that's trapping air. I think the answer may be to swap in another MC with the standard size ports, and rebend those lines.

2. which reservoir feeds the front brakes, the one closer to the booster or the other? The MC I current have has different sized outlet ports (hence; the adapters), which seems to strongly suggest there's a preference. Recap: '69 Bonne MC for power 4-wheel drum brakes.

[misterp266]

Here’s the MC I ended up getting for my ‘63 Catalina.
Fittings on both sides and can be used with or without a booster and can be used for drum-drum or drum- disc setup. I got the aluminum version for less weight and no rusting. Going to change to a cad plated cover.
No, it has not been plumbed yet. Plan to use the outside ports and an adjustable distribution block. Scarebird disc on the front and drum rear. Manual brakes.

https://piratejack.net/gm-universal-...ster-cylinder/

[MOJO Catalina]

Originally Posted by Keith Seymore

Subscribing (so I can find this when I need it).

Just lost the brakes on the GP last night (single system). Made it home safely by downshifting the trans and with what little brakes I had left, but getting the car in the garage was a challenge!!

K

Scary situation.. I lost brakes in my '63 GP pulling into a parking space at a grocery store.. Luckily there were bushes in front of the space that were about 5 feet tall and had been there for 10 years. I usually park just anywhere but on that day Chief Pontiac must have been watching over me.. The pedal grabbed for a split second then went right to the floor.. I sailed right into the bushes.. No damage, just bent the bush out the other side.. When I pumped the brakes a few times they started grabbing again.. the seals in the MC must have gotten some rust buildup around them, allowing the fluid to blow by them.. I abandoned the grocery run and drove home slowly with one foot on the Emergency brake... It could have been bad if I'd plowed into a car or someone and their cart.. Did the dual swap the next day.. ( car sold years ago) Now both my drivers have them. The '60 Cat is manual drum/drum and the '63 BV is power drum/drum..

[Young Pontiac Guy]

Ramyak, did you come up with a. Part number?

I am doing a front disc brake conversion on my 62 Catalina. It currently has power drums and a single master cylinder. Want to get a new dual master cylinder and be nice to add a prop valve. Would a later Catalina with front disc and back drums setup work out ok? Any other suggestions?

Thank you,
Joel

[WQ59B]

Have bit the bullet and procured a '65 Cadillac MC- it's ports are on the engine side and aren't oddball-sized / requiring adapter fittings. Hope to mount next week and resume bleeding.

[Keith Seymore]

Originally Posted by Keith Seymore

Subscribing (so I can find this when I need it).

Just lost the brakes on the GP last night (single system). Made it home safely by downshifting the trans and with what little brakes I had left, but getting the car in the garage was a challenge!!

K

Ok - so I've gathered all the parts and have started the teardown....and already hit a couple snags.

a) I'm using the Autozone M-1328 master cylinder for a '69 Bonneville. I've added the adpater fittings to the outlets and, when I position the master cylinder, I've got hard contact with the wheelhouse inner. There's not enough room to add a brake line and make the turn. Anybody else experience this?

b) The removed single pot master cylinder has a very deep bore in the piston for the push rod; the new master cylinder has just a small dimple to position the push rod. I'll need to take quite a bit off the push rod but - how does it come out from the booster? When I pull on it it comes out a bit but feels like it is attached to a/the diaphram and sucks back in when I let go.

c) I sent a note to one of the brake engineers relative to the port placement. He was off for the GM shutdown but I'll let you know once he replies.

d) Do you all have a preference - should I keep posting here or should I start a new thread specific to my conversion?

K