bob p

I have a 1962 Super 88 with PS, PB, AT. It has a Bendix booster and master cylinder.

I need to so some brake work, so I'm thinking this would be a good time to change the MC over from the old single-chamber type to a more modern dual-chamber type for safety reasons.

Looking at my Raybestos catalog, the part number crossover for the original Bendix MC is a Raybestos MC35026. It uses the 4-bolt mounting system to attach to the Bendix booster, rather than the more recent 2-bolt system.

I'd like to know if anyone can help me to determine what model of MC would be a suitable dual-circuit replacement for the old-style single-circuit MC. I'm hoping that somebody knows enough about pushrod length to recommend a suitable direct bolt-on replacement. I'm trying to avoid taking apart the booster to change op-rods if I can find the right MC with the proper pushrod spec. Finding a MC that has an outlet port that matches the original outlet port would be an added bonus, as that would simplify the plumbing.

Looking at the catalog, the MC specs list the outlet port size, but they don't say anything about pushrod length.

Any help would be appreciated. Thanks.

bob p

Just in case I wasn't clear, the dual-circuit MC that I need will be for a 4-way drum PB system, not for a disc/drum conversion. I'm going to keep drums on all fours, and stick with the 1.0" diameter MC.

Thanks again.

Oldskeeper

Bob, I was told that the 66 Caddy was a direct bolt in but I haven't tried it yet. The ports are on the engine side so you don't have to carve up the inner fender to clear the lines. I checked a bunch out on evil bay to compare and try to figure out what would work for my 62 wagon.
Steve

bob p

I don't know enough about the differences between the Moraine and the Bendix boosters from the different years to be able to confirm that the 66 Cadillac MC will work.

The Raybestos catalog that I've been looking at says that the correct MC for a 1966 Sedan DeVille is the Moraine-type, MC36373. I have no idea whether there are any compatibility differences in using any particular MC with either a Moraine-type MC or a Bendix-type MC. I also don't know whether there are any year-to-year differences in the boosters between my 1962 single-circuit setup and the 1967-69 dual-circuit setups that will complicate the proposition of a clean bolt-on replacement of a new master cylinder with my 1962 Bendix booster. I'm really hoping that someone who knows about this stuff will be able to help.

The best that I can tell from the catalogs (which don't say anything about the piston and pushrod) is:

* The 1967 Cad and 1967-69 Olds Delta 88 seem to use the Moraine-type power booster with a Moraine-type master, which crosses over to Raybestos MC36234.

* The 1967-69 Olds Delta 88 with manual brakes crosses over to a Raybestos MC36235. (Not interested in that one.)

* The 1967-69 Olds Delta 88 also seems to use the Bendix-type power booster with a Bendix-type master, which crosses over to Raybestos MC26236.

I don't know enough about this to even know if I'm close to being on the right track.

bob p

Before starting this thread I emailed Raybestos Tech Support for help. This morning I called the Raybestos / Brake Parts Inc. technical support line for assistance, and the results were really disappointing.

Last night before I started this thread, I had emailed the Raybestos tech support department about this topic. I asked them if they could help me to determine which dual-pot MC would be a suitable replacement for the original single-pot MC. Here's the email reply that I received:

Now that is odd. For me, it's a safety issue to drive around with a single-pot MC, but for Brake Parts Inc., it's too much of a liability issue to assist in determining how to replace a dangerous single-pot MC with a more safe double-pot MC.

Since they weren't willing to provide a direct answer to the question, I called them on their tech support line to ask for specifications so that I could independently determine the answer to the question. Unfortunately I got different answers from the same guy every time that I called.

Instead of directly asking for a replacement for a specific application, I asked them for MC specifications so I could determine what MC was suitable for an unspecified custom application. Knowing that the stock MC35026 piston diameter for my application is 1.00", I asked for the length of the piston pushrod recess, and for either the stroke distance or the stroke volume of the MC.

Unfortunately, I was told that BPI's computer system doesn't have computer-searchable specifications. I was told by the support staff that every time I wanted specs on a master cylinder, they had to pull a blueprint and read it for me. The support staff guy seemed to be really annoyed by the idea of having to look at blueprints. When he pulled the MC35026 blueprint I was told that the measurement was "an inch and a quarter."

I called back about 10 minutes later as a courtesy -- to notify their tech department that I had determined that their published specs for WC32071 (front wheel cylinder) were wrong. They had published the inlet thread size as being 3/8-24 when the actual thread size was 7/16-20. This error was present both in their hard-copy catalog and in their online lookup tables. I wanted to pass this information along to help clear up any confusion that might be generated by the web site giving out improper specs. According to the web site, the same brake hose BH36611 is used for both front wheels, even though the hard copy and web site catalog specs both say that the WC32071 and WC32072 inlet thread sizes are different. They are different because the 071 spec is wrong and the 072 spec is right.

The BPI technical support attendant pulled the blueprints on both WC32071 and 072 and verified that the inlet thread size was 7/26-20 and that the catalog's reference to 3/8-24 was wrong. I asked if he could give this information to the catalog people to correct the error. He seemed disinterested in helping to make sure that this mistake got corrected because it wasn't his department's job to do that.

After I passed along the info about the screwed-up specifications, I asked him for additional specs on my stock master cylinder, MC35026. He seemed annoyed about having to pull another blueprint. I think that this is because my phone call interrupted a conversation that he was having with someone else, and he wasn't very interested in helping me. I think their blueprints are computerized images, because the lookup only took him a few seconds, and I could hear him and another person laughing in the background as he did the lookup.

This time he told me that the piston's recess for the pushrod measured 1.562", not "an inch and a quarter" as he had told me only a few minutes earlier. When I asked him to verify that he was looking at the right blueprint because he had given me a different measurement on the previous call, he told me that I was wrong, that he had told me 1.562" and not "an inch and a quarter" on the previous call. That just wasn't true.

Then I asked him to tell me the stroke length for MC35026. He told me that the stroke length measurement was not listed on the blueprint! Because of the discrepancy in his answers about pushrod cup depth, I asked if it would be possible to look at a copy of the blueprint to verify the measurements. I got a strict "no" response from him as BPI won't share their blueprints. I guess that's understandable.

I encountered several problems in getting assistance from Brake Parts Inc.:

1. The BPI tech support person wasn't very interested in helping me on my call. It was obvious that he was in the middle of a fun conversation with someone else at work, and that having to answer my call was getting in the way of what he really wanted to do.

2. Brake Parts Inc. tech support person was totally disinterested in an incoming call that identified an error in their published catalog. He seemed totally disinterested in correcting errors because "that isn't my department."

3. Brake Parts Inc. is totally avoidant when it comes to assisting with a single-pot to dual-pot MC conversion. They want to avoid getting involved to avoid liability.

4. Brake Parts Inc. tech support gives out errant technical specifications. On two different calls that were placed only a few minutes apart, I talked to the same guy and I got two different specifications for pushrod cup depth. When I identified the discrepancy, the support tech lied to me, telling me that I was wrong and that he had given me the decimal spec on my previous call. This gave me pause to ask myself whether this guy was really competent.

5. Brake Parts Inc. either can not or will not give out complete technical specifications. I asked for the stroke distance (or the stroke volume) of a master cylinder so that I could independently determine a suitable replacement. The tech support person claimed that they had no such specification in the blueprints.

It's hard to imagine that a manufacturer's master cylinder blueprint and/or spec sheet wouldn't contain either the stroke distance or the stroke volume. This, along with getting different answers every time that I call, makes me wonder how competent their tech support personnel are, and whether I should trust their responses. It would seem that they are either incompetent, or if they sense that you're trying to do something that their legal department tells them to stay out of, they either purposefully give out bad numbers, or they avoid giving out numbers altogether.

Unfortunately, this poor performance from Brake Parts Inc. makes it very difficult to perform a safety upgrade on a car that has a single-pot master cylinder.

Prior to this, I had been a big fan of BPI products. I've used their Raybestos or NAPA products for total system rebuilds on 5 of my cars. Now that I'm getting such poor performance out of their tech support staff, I'm having serious doubts about whether or not my brand loyalty has been misplaced.

Back to the original topic -- can anybody help with the dual-pot conversion specs?

bob p

Update: I called BPI tech support again, this time to check pushrod depths on a different MC. I talked to the same guy, who seemed just as disinterested in being helpful today as he was yesterday. When I asked for pushrod cup depths for a specific MC, again I got two different measurements out of him. I gave up on Brake Parts Inc.

I called Dorman. The fellow there was very helpful. Unlike the guy from BPI, when I told him that I was trying to do a single to dual pot conversion, he was willing to help. When I gave him a Dorman part number for a MC that I was interested in, he pulled a stock MC from their shelves, took a precise measurement for me, and called me back within a half-hour.

The long and short of it is that the guy at BPI was a total numbskull who wasn't interested in helping, and the guy from Dorman was both well-informed and helpful. I ended up ordering the Dorman master cylinder.

Oldskeeper: it looks like the 1966 Cadillac MC will work for me. Lines that exit on the fender side just won't fit, and lines that exit on the right side are essential. Also important is the pushrod depth (headspace) adjustment. I was a bit worried about the fact that I have a Bendix booster and the 1966 Cadillac MC is designed for a Moraine booster, because I have read that the power brake pushrod lengths were different between Bendix/Moraine, but later became the same, and I don't know the year that the changeover took place.

I tried to find the booster pushrod adjustment specs for the 1966 Moraine unit but I was unsuccessful in finding the 1966 Cadillac service specs. Because the 1966 Moraine booster specs weren't available, I decided to compare MC specs. I did some homework comparing the actual pushrod depth of my single pot original MC's piston and the dual pot Dorman MC's piston. The measurements according to specs are within about 75 thousandths of one another. If you have an adjustable pushrod (Bendix booster) then you should be able to tweak-in the proper pushrod headspacing using the pushrod adjuster threads.

Oldskeeper

Good to hear that it will do what you need, I have both bendix and moraine here on my 62s and 63s, my 62 starfire has a dual master cylinder that it came with and I plan on switching it over to my 62 super 88 wagon. When I get to that point I'll let you know how it worked out.
Steve

Higgins

Bob p, so what Dorman part number did you order>
? I have a 63 Starfire I would like to change out to a dual as I lost my brakes a couple years ago because of a leaky rear cylinder, barely made it home.

Charlie Jones

Bob , The difference between Bendix master cylinders and Moraine is that Bendix cylinders used 4 bolts to bolt the master to the booster and Moraine only used two .
A 66 Cadillac master cylinder is a Moraine cylinder and will not bolt to or work with your bendix booster.
However , if you can scout out a 1962 Olds Moraine booster it will work with the 66 Caddy master cylinder.
It must be a 62 booster as 61 and 63 were both different.

bob p

My comments are going to be specific to my 1962 Super 88. I don't know anything about 1963.

It's very easy to become confused by the differences Bendix vs. Moraine brake systems. As a general rule it's a good idea not to mix and match systems designed by different companies, but in this case I *have* to do this, because Bendix didn't make any 4-bolt, dual-circuit master cylinders, that were designed for my 1962 Super 88.

I agree that Moraine used a 2-bolt mounting system and that Bendix used a 4-bolt mounting system. I also agree that a 1966 Cadillac MC is a Moraine-type unit. Based upon the extensive research that I have done into the problem, I have to disagree with all your other comments that a 1966 Cadillac MC will not bolt to or work with my 1962 Bendix booster.

I guess it's fair to say that so far I'm only basing my opinion upon extensive research on the subject, and dry-fitting the actual products on my totally-original 1962 Super 88 to verify fitment. I suppose that I could run into some unexpected problems when I energize the system, but so far the fitment looks just fine.

Higgins, I didn't mention the Dorman part number because the Raybestos and Dorman part numbers are the same. The application that I used was 1962-1966 Cadillac. IIRC almost all of the Cadillacs in that period used the same master cylinder. Any Fleetwood or DeVille in that period should cross-reference to 36373.

Oldskeeper

Bob, can you use an adaptor plate clamping the moraine M/C to the bendix booster?
You could bolt a plate to each side clamping the M/C against the booster so you still get a seal and if it is over the ends it would hold tight the same as being bolted directly to the booster keeping all of the dimensions correct.
Steve

bob p

Steve, I don't want to jump the gun and go giving out bad advice that I don't even know is bad advice, because I haven't finished this project yet. for all I know, all of the research that I have done could have made me draw the wrong conclusions and I could be totally wrong and Charlie could be totally right. So when you read this, bear in mind that you shouldn't take my word for anything until I have a chance to report back after I finish the conversion and test it for proper function.

That said, the 2-bolt Moraine-type MC bolts onto my Bendix booster just fine. Using the bottom two mounting studs the MC bolts-on with the proper geometry for the booster pushrod to enter the MC's pushrod cup. I haven't done a precision measurement to compare MC piston pushrod cup depth, but my preliminary measurements agree with the tech specs, and it looks like the headspace is going to be fine. If it's not, my Bendix-type booster does have adjustable headspace on the pushrod.

Regarding the O-ring seal: it's too early for me to comment about that. Maybe someone else can comment about any o-ring differences between bendix and moraine type boosters.

I was planning on not saying too much about this until the conversion is done, but here are some pictures that demonstrate the fit:

bob p

As you can see there is no way that a master cylinder that has exit ports on the wheel side will fit. The exit ports on the engine side turn out to be very close to other components, so routing of the brake lines will make things crowded.

Charlie Jones

Bob, Get a Moraine booster or forget about changing to a dual system.
WHAT YOU ARE THINKING ABOUT DOING IS DANGEROUS . I TOLD YOU IT WILL NOT WORK.
Bendix and Moraine components are different and cannot be mixed.

D. Yaros

Being a 62 owner with a Bendix booster, I can say this is a project I and others would be interested in. Understand you hesitancy to give out bad info without even knowing it is bad.

So, when you do get it all figured out I and others would appreciate your documenting the project with photos, part #'s and text so that we might also undertake it.

Goof luck and I shall be following developments.

bob p

Maybe this thread belongs over at The HAMB.

Charlie, can you offer any specifics about why this combination can not work, and specifically point out what deficits in the system would render it unsafe? Or are you just repeating rules of thumb that you're familiar with?

FWIW, I'm not blindly mixing and matching parts and hoping for the best. I've spent many days and nights pouring over numbers and calculations, deciding which components should be candidates for the conversion. Once the specimens have been obtained I've taken great care to disassemble all of the required components, take measurements, and do the engineering math to verify that things should work properly.

I'm looking at obvious things like pedal ratio, boost, linear piston travel, piston diameter, squirt volume, hydraulic pressures and the geometry of the sealing of the booster to the MC. This project is still very much in the design stage and it is by no means complete, so I'm open to anyone's suggestions and comments. If there is something specific that you can identify as being a problem, I'd appreciate as much specific detail as possible so that I can double check everything.

It's unfortunate that there are no turn-key solutions to the problem of upgrading from a single-pot MC to a dual-pot MC. That sort of safety upgrade requires deviation from the OEM/stock configuration or it's never going to happen. In the worst case scenario, I'd feel a lot more safe eliminating the booster completely, and driving a car that has a modern 2-circuit set of manual brakes than a car that has an inherently unsafe single-circuit set of power brakes where the braking system is at risk of going into total failure mode should it develop a leak.

The way this thread is heading, I'm beginning to think that I need to stop disclosing what I've been doing, especially if the results end up being as good as I'd like them to be. Unfortunately, taking that approach would require that I keep all of the information to myself, and leave guys like Steve and Dave out in the cold.

Oldskeeper

Bob, I sent a PM,
The wheel cylinders are non specific as they work on both types so that won't be a concern. The M/C bore is the same s the single M/C so the volume of oil is the same, correct?
The booster is the same dia. with either system. So the only variable would be position and peddle travel, the rod is adjustable so if set to the correct length then it should function properly and staying 4 wheel drum the new master cylinder won't require a proportioning valve and should still have the correct ratio between front brakes and rear ( 60 front 40 rear)
What am I missing?
Steve

bob p

Charlie's warnings are exactly the kind of warnings that you'd expect to hear from a professional mechanic.

Steve, knowing that you have enough stroke volume to fully extend all 4 wheel cylinders is essential.

Knowing that both masters are 1" diameter helps, but that doesn't give the complete picture. Stroke volume will depend not only on the MC piston outer diameter, but also upon the MC chamber's inner diameter (outer diameter of the piston where it is skinny inside of the chamber), chamber length, and piston travel/displacement. I don't assume that everything is the same just because the bores are all 1.0". Knowing the fluid chamber inner/outer diameter, bore length and the stroke displacement are all needed to calculate stroke volume.

Another way to estimate squirt volume before disassembling and/or volume testing the dual-pot master cylinder candidate is to compare the volumes of the wheel cylinders. As a simplistic example for screening purposes, the Olds application uses a pair of 1" wheel cylinders in back and a pair of 1-1/8" wheel cylinders up front. The 66 Deville uses (according to Raybestos catalog) a 1" rear wheel cylinder and 1-3/16" front wheel cylinders. If the systems were adjusted so that the linear displacement of the wheel cylinders were the same, the Cadillac would require more stroke volume than the Olds application because it has 1-3/16" wheel cylinders vs. the Olds' 1-1/8". In other words, looking at wheel cylinder specs suggests that the Cadillac MC offers more stroke volume than the Olds setup requires. That sort of guesstimate is OK for MC screening purposes, but it needs to be followed-up with real-world measurements of the master cylinder.

Bear in mind, these are just seat of the pants numbers for use as an example -- I'm not providing all of the calculations that you'd need to do to design your own setup. Before trusting a real-world application it would be good to look at system pressures and volumes.

I need to stop typing and get outside to do some work.

Charlie Jones

Bob , I worked on these cars as a mechanic back in the sixties and seventies .
If we got a master cylinder that was the wrong type we would send it back and never make an attempt to "make it fit". Why ? Because it was on a brake system and modification would open us up to "a real can of worms" as far as liability if the car was ever in an accident.
All it takes is a scheister lawyer to point out that you made an unauthorized modification to the brake system, whether or not it was the real cause of the accident , and you can be liable for the damages.
There is nothing inherently unsafe about a single master cylinder system. IF IT IS PROPERLY MAINTAINED. If you use new cylinders, new brake hoses, and make sure that the steel lines are not rust pitted anywhere , you can be confident that you can stop every time you put your foot on the pedal . We did so for many years before the advent of dual master cylinders.
If you do decide to do the conversion to dual M/C a 1962 Olds MORAINE booster can't be that hard to find.

bob p

Thanks, Charlie. I understood your message to be that it would be a liability problem for a mechanic to make any non-factory-authorized modifications to any brake system. As far as the lawyers are concerned, anything that is different from factory spec -- like a disc conversion which might actually improve braking performance -- is BAD BAD BAD. Any amount of change from factory-spec only exposes a mechanic to shop liability.

If the lawyers had their way then no car would ever deviate from factory spec, and the entire world of rod and custom cars wouldn't even exist.

I understand where you're coming from. But I still can't find a 1962 Olds Super 88 Moraine booster. If anyone can point me to a place where I can buy one, please do. I've been looking and haven't found a source. This thread wouldn't even be here if I could find one.