2 bolts aluminum master cylinders.

[Remow2112]

In 1980 there are 2 master cylinders listed for the Volare. 1 for manual brakes and 1 for power.

Cardone 101822 for power
Cardone 101821 for Manual.

They look identical, no one seems to have a 101821 in stock to examine. Does anyone have have a manual 2 bolt aluminum MC laying around? I would like to know how deep the channel is for the push rod.

I am not convinced that there is a difference between the manual and power. All the stats are identical. But finding info on how deep the push rod hole is seems to be impossible without laying hands on 1 and measuring.

 

[BudW]

The manual brake Master Cylinder has pressed in studs to attach to firewall and comes with either the arm or the rubber grommet (called a clip) that holds the arm in place (I've seen 'em come both ways).

This is a picture of a used '78 F-body master cylinder:

Are you looking for a replacement master cylinder for a car with manual brakes OR thinking about converting to manual brakes?

Edit: if looking for an NOS unit, my '80 parts manual shows these part numbers for FMJ's:
4131288 - Manual brake w/clip (no arm)
4205972 - Power brake

 

[Aspen500]

I believe, other than the studs and rubber ring for the pushrod (which generally stays on the rod when it's pulled out), they are the same master. Same pistons, same bore.

When I replaced mine quite a few years ago, I bought and brand new master from Napa (I think it was). It didn't come with the studs pressed in. Had to press them out of the old one. As I recall, there was no choice of power or manual. The reman ones from Napa do have that choice BUT, don't include the studs with the manual one so no idea why they list them 2 different p/n's.

 

[Remow2112]

Thx for the replys.

Since I have no patience, I pulled the power brake master cylinder off a 79 aspen and took a 4 to 2 adapter plate and bolted it to my Volare.

It currently has manual brakes and the reinforcing plate. I had the old style cast iron 4 bolts (500 pound LOL) master cylinder. The depth for the plunger between the manual for a 1977 and a power brake aluminum 1979 is identical. So I bled it and stuck it on the car.

It is awesome and works great. Better pedal feel and less effort to stop then the old cast iron. It is possible that cast iron might have some rust issues in the bore but I don't think so. Pretty sure there is no difference between the power brake and manual master cylinder.

In my case the studs are not pressed in and are on the 4 to 2 adapter I used. I don't have the really cool, long cone rubber piece like budw pic. But it works. So I am not sure exactly why it is 2 separate part numbers but it is possible Chrysler didn't want to confuse the dealership service department.

 

[BudW]

The problem with cast iron is rust (gasp, a 4-letter word)!
Brake fluid should be replaced every two to three years because it will normally absorb water moisture. This is one reason to keep brake fluid in tightly closed containers.
The water moisture lowers the boiling point of brake fluid which is not good for the braking system. Also, it causes rust (water moisture, iron (or steel) and air (when the fluid temporarily evaporates when it gets hot. rubber parts that move across rust (like in a master cylinder, brake caliper or wheel cylinder) causes the rubber to wear out and start to leak, which then snowballs.

Aluminum is much better with this and doesn't have the rust problem nor wears out the rubber seals near as fast. To boot, it is much lighter, as well. Aluminum can corrode if not coated - but corrosion is not as bad of a problem as rust is.


The only concern I have is the '76 to mid-year '78 firewalls (that use cast iron master cylinders) have a different bolt-pattern than the late '78 to '89 firewalls (that use the aluminum master cylinder).
Both have six holes (upper and lower holes are for the brake booster). The iron manual master cylinder uses the two bottom and middle holes. The manual aluminum master cylinder only uses the two middle holes, which are in a different location than the iron middle holes.
That said, if you are using a 4-to-2 bolt adapter, then you might have fixed that concern already. Not having the master cylinder in the correct location will cause it to wear out faster due to unintended side forces.

Here is a picture of the aluminum master cylinder firewall reinforcement plate - which looks different from your cast iron master cylinder firewall reinforcement plate:

This came off of the same car as the master cylinder pictured in post #2
BudW

 

[Aspen500]

At work we used to replace iron masters all the time, when there were still a lot of them on the road. Aluminum masters get replaced VERY seldom. They just seem to last for the life of the vehicle. I only replaced mine with a new one during the big build a few years back, "just because". The original worked just fine yet.

 

[Remow2112]

That is some interesting info. I used to think I knew a lot about the F body till I started reading your posts Budw.

Some info on my race car. It is a 77 Volare Roadrunner that I bought off my boss in October of 90. It was his wife's college graduation car. They were going through a divorce and she just left it at his house and told him to get rid of it. 318 2 barrel console car. First car I ever bought at 60 feet. (Saw it at 60 feet and knew I was going to buy it.

It was my daily driver for 10+ years and then there was this streak that every time I turned around someone had hit it. After the 4 time in 6 months someone tagged it and replacing the drivers door a 3rd time. I pulled her off the road and started fiddling with her for mostly race track duty.

That has lead to multiple engines. (on number 15) everything from mild intake, header, cam add on the original 318 to a 10.5 compression 360. It is currently running a BB 400 and does 12.4 in the quater.

In all the experimenting and various engines and tranny combos at some point I tried to use an A body power booster and master cylinder. Never could get it to work right, but it required drilling some holes. So to make this long story shorter, I have multiple holes in that area and I don't recall what I pulled my manual brake plate. But my brother believes it was 1980 Aspen.

The brake plate I have and the 4 to 2 adapter all lined up correctly and the brake push rod is perfectly level. I have a 78 Duster in the backyard. When get a chance I will pull the power booster take a look at the firewall holes. I am curious.

It is good info about the iron master cylinder. I live in Tucson, AZ and we don't get a lot of rain and very little humidity. So it is surprising to me that water would get into the brake fluid. But it must have because the rear wheel cylinders were rusted. So if the rear wheel cylinders are rusted then most likely there is rust in the master cylinder.

 

[Aspen500]

Water get into the brake fluid from the air. A little leaks in through the caliper/wheel cyl seals over time and can even migrate through the castings to some extent, and of course, the master caps are vented. Probably not as big a deal in Arizona as it is here in WI where the humidity is higher. Brake fluid absorbs moisture anywhere it can get it, unfortunately. DOT 5 doesn't absorb the moisture, you end up with water bubbles basically. In Tucson no problem really. Up here on a winter driven vehicle, big problem. At -20 water bubbles in the brake system would be a very bad thing, lol.

 

[Remow2112]

Yikes. Water bubbles does sound like it would be not good. LOL

 

[Mikes5thAve]

So I am not sure exactly why it is 2 separate part numbers but it is possible Chrysler didn't want to confuse the dealership service department.

It's probably the parts they came with or some difference that doesn't really make a difference.

 

[BudW]

DOT-3 and DOT-4 brake fluid is one of those things that loves to pull water moisture out of the air. There is a name for it, but can't remember what (and too lazy to look).

The problem with brake fluid absorbing water, is heat and what happens to iron when around water. I think it would be a very good thing to put brass sleeve inside of an iron master cylinder, brake caliper and/or wheel cylinder - for then rust wouldn't be as much of a factor.
Honestly, aluminum might be the best thing to happen to master cylinders. I think there are some important factors why aluminum is not widely used for brake calipers or for wheel cylinders.

If wheel cylinders were not as cheap as they are (um...China), I think pressing in a brass sleeve then re-drilling it would make for a lifetime fix (with the occasional broken/damaged bleeder).
Aluminum for a master cylinder is a no brainer. A lot of dead weight there vs. the cast iron version and, again, maybe one of the best upgrades a person can make (if you have an iron one.

If you do have your brake apart again, I would recommend at least looking into the smaller K-car brake booster setup. I have one for my '86 Fifth Ave big block change-over.
Not yet decided about keeping power brakes on my '77 wagon (before its big block change-over) which why I have the manual brake parts for it, now. I might change it to manual brakes first before coming to a decision on it. That said, the FMJ brake booster is just too big physically and too powerful for most of us, so if keeping power brakes on my wagon, it will also get a K-car booster.

Note: there are a few posts in this forum board, that I have contributed to, that talks more about the K-car booster.
BudW

 

[Remow2112]

Actually have read your stuff about the K car booster. I actually have bought a booster and plan on giving it a try this coming winter.

 

[DCAspen]

Slant Six Billy put a K booster on his 76'

 

[BudW]

I actually have bought a booster and plan on giving it a try this coming winter.

For whatever reason, most brake boosters come un-painted. It makes sense to give it some (paint), unless you are going for the rusty look (in a short time frame).

Powder coating would be best sense (DOT 3 and 4) brake fluid "eats" paint BUT powder coating needs heat to set the powder (I "think" about 400' F (200' C) for about 15 minutes) - which might be too hot for the rubber diaphragm(s), seals and/or plastic separator inside of the booster.
I don't recommend taking one apart due to the spring inside - but there is not much inside of a booster. It is mostly empty.
BudW

 

[Remow2112]

What is the least vacuum you can have and still keep it functional? I believe I am right around 12 - 13.

 

[BudW]

I can't answer that (someone else might, though). I've never had an engine not produce vacuum before (except for my diesel pickup).

The dual diaphragm booster should help (over the single diaphragm).
If nothing else, some car companies are making an inexpensive electric (bolt on) vacuum pump to run the vacuum brake booster (think turbocharged gas or diesel engines). My '97 diesel has a timing gear driven vacuum pump, and not helpful to your case.
BudW

 

[Mikes5thAve]

The diagnostic chart in the service manual seems indicate you need min 12" of vacuum for it to work.
Don't forget that it usually holds pressure and you can get a pump or two out of the pedal after the car is shut off so if you are producing more vacuum while driving it might keep that higher level.

 

[Bill Park]

The 505 that we are building will not make 12 inches . Oh well the booster is in the way anyhow.

 

[Aspen500]

BudW, I think the term is hydroscopic for a substance the absorbs water or moisture.

 

[BudW]

BudW, I think the term is hydroscopic for a substance the absorbs water or moisture.

That's it!
I was too lazy to look it up.

I have a 3-D printer and some of the plastic filament (what the printer uses to build projects with), which is 1.75 mm (1/32") in diameter, that is also hydroscopic - which means if I don't extensively dry it before use (which is a pain) or find a way to keep it dry (in a vacuum), then your print jobs fail miserably (it looks like someone took a torch to plastic). The print head is twice the boiling point of water and the steam escapes when heated.
Not quite the same thing, but materials absorbing water is not always a good thing.
BudW