I just finished up upgrading the brakes on my father’s 1980 El Camino. This is a daily driver that I am testing several different master cylinders for a manual brake conversion swap. His brakes worked good before exchanging out all the parts, but I wanted to take out most of the variables when testing master cylinders. First and foremost, I wanted to make sure this 1980 El Camino did not have quick take up front brake calipers. In my research, quick take up calipers will make it difficult do get good pressure to the caliper when using manual brakes.

Here is the rundown of the parts I used:
• Speedway Motors Big Bore Metric Calipers - PN# 91031040 $59.99 each
• Bendix Titanium metallic front brake pads (FF Rated) - PN# MKD154 $38.22
• Turned the stock rotors $30 Local Auto Parts Store $15 each
• Edelbrock/Russel Stainless Steel Braided Flex Lines PN# 692100 $54.80
• Wagner 7/8” Wheel Cylinders from an manual brake S10 PN# F110261 $13 each
• Wagner Thermo Quiet Rear Shoes (EE Rated) - PAB514R from O’Reilly’s Auto $32.99

The Speedway Motors big bore metric calipers (2.75” bore v 2.38” bore standard) came with brake pads, but the pads did not have a rating on them. I DID NOT want to use a brake pad that would need a lot of heat to be effective. The weight difference between the two calipers is less than ½ of a pound. This is a daily driver and not an autocross car, so I chose the Bendix Titanium pads because my research and reviews showed them to have good cold clamping friction. Based on the EE rating, the rear shoes should also have good cold stopping abilities. Look on the pads or shoes when you buy them to make sure they have a rating on them. The higher up the alphabet you go the hotter the pads will have to be to work effectively. Pads or shoes with no rating on them should be avoided.

It was surprising to me to find a 24mm strait bore aluminum master cylinder on this 1980 El Camino. I didn’t know they made aluminum ones with a strait bore for g-bodies. I had always been under the impression, because it was aluminum, that this was a step bore master for quick take up calipers. I do know for a fact that any NEW replacement master cylinders for g-bodies will for than likely be cast iron. So if you want aluminum master cylinder for power or manual brakes that bolt up to your brake lines, a rebuilt master cylinder may be your only option.

I changed out the 30 year old rubber brake lines with the braided stainless. The front lines were a little longer than the originals, but I routed them so they were not touching any suspension pieces. The rear was a little more difficult to replace because the clip that holds the rubber line to the frame was difficult to get at. The new braided rear line was fairly easy to install also.

The hardest part to the entire swap was installing the rear wheel cylinders. Getting the clip off was not too bad, but getting the clip back on was a pain. I did it with two c-clamp, and open ended wrench, and the lid off of an old battery terminal cleaner (don’t ask for these details because I do not recommend doing it this way. G-H-E-T-T-O).

After the system install, bleeding the fluids, and bedding in the pads and shoes I took it out for a spin to test the brakes with the same master cylinder and vacuum booster from the original test with the original brakes. Even though I was able to easily lock up all four wheels, it seems to have a little more pedal travel before you could feel the brakes start to grab. I believe this has to do with the increased piston area in the front calipers and rear wheel cylinders while using the strait bore 24mm master cylinder. The 24mm master cylinder will have more pedal travel to fill the extra volume of fluid required by the calipers and wheel cylinders.

If keeping the vacuum booster, it might be best to step up to the step bore master cylinders that are used on the 1981 and up g-bodies. The primary bore is still 24mm, but it also has a larger step bore of 36mm that will increase the volume of fluid to the larger calipers and wheel cylinders.

The manual brake conversion went well. I kept the stock , 31 year old, 24mm master cylinder that came with the stock power boosted brake system. I kept the 24mm master, for now, because I upsized the front calipers and wheels cylinders. It stopped the car ok, but I felt I still had too much pedal travel and I couldn't get the front brakes to lock up. I am going to rebleed the calipers, unbolted from the spindle, to point the bleeder screws up at the 12 o'clock position. If this doesn't do the trick, I will bolt on a brand new manual brake master cylinder from a 1978 to 1980ish g-body. This master cylinder has a smaller bore which should give me higher pressure at the pad.

Before manual brake conversion:




After manual brake conversion:

I rebled the front calipers unbolted from the spindle to try and get rid of some of the spongyness in the pedal. I did this to see if there was any more air in the system at the caliper by rotating the bleeder screw at the 12 o'clock position and bleeding the system. No air at the caliper, so I think the origanal 31 year old master cylinder has air in it or it is bad.

I am going to replace it with a new 7/8" bore master cylinder from a manual brake 1978 g-body ($60 from amazon). Though it is made of cast iron, it is the smallest bore master cylinder that readily bolts on. I know of no aluminum master cylinders that are 7/8" bore that will readily bolt on, other than one of the expensive aftermarket ones. I would also like to test a master cylinder from a Dodge Dakota. It has a 24mm bore, is aluminum, and with one brake fitting adapter, it bolts into place with the adapter plate I am using.

Here is the pushrod assembly I put together that is in my dad's El Camino.

It is adjustable from roughly 3.75 inches to about 4.25 inches.

Blown apart


Assembled Top View


Assembled Side View

So how well do the brakes work now Dave ??? Unless I'm missing something,this looks like a fairly easy modification,and cheap too.I have previously upgraded my front brakes very similar to what you have done,although I used the USBrakes oversize metric calipers,Hawk HPS pads,slotted & crossdrilled rotors and Russell braided SS hoses,and the Ford 9 inch has rear drums much bigger than stock.The brakes work much better than stock but the vacuum runs out after a couple of pumps.I bought an electric vacuum pump,but I am reluctant to clutter up the engine compartment with it,and yours sure looks pretty clean without the booster.So tell us a bit more on how your dads brakes work,and how big a job it was too change over to manual.
Guy

The car stops OK with the 32 year old 24mm bore master cylinder it has on it now, but I cannot get the brakes to lock up. There is some sponginess in the pedal that I suspect is either a bad 32 year old master cylinder or I have air in the rear brake lines somewhere. I am waiting for my brand new 1978 Malibu 7/8" bore manual brake master cylinder in the mail to change over from the 24mm bore strait bore.

Hardest part of the install is bolting it to the firewall. You will need a someone else to help align everything up and bolt it down to the firewall. The pin (stud) will also need to be pressed into the brake pedal using a press. If using a plate without a retention cup, it bolts directly to the firewall with no modifications to the firewall. With a plate with the retention cup, the firewall will have to be trimmed a little to clear the retention cup.

It is really not a hard job to install a manual brake system. The hardest part is getting it to work correctly.

There are usually 3 main reasons why manual brake setups on g-body cars, s-10 trucks, and 3rd generation Camaros/Firebirds do not function well.

1. Low drag calipers
2. The small piston diameter in the low drag caliper
3. The master cylinder

You and I have numbers 1 and 2 covered above which takes out most of the variables. I am working on number 3 by testing out master cylinders and narrowing down which ones work best with my setup.

Very interesting Dave,please be sure to keep us updated as you go,and take lots of pictures.So what,if any,is the advantage,or dis-advantage,to using the retention cup ??
Guy

I will keep you updated. I am waiting for a 1978 Malibu manual brake master cylinder with a 7/8" bore to install and test.

Because the manual brake master cylinder from a g-body has a shallow cup to retain the pushrod (actually it is just a dimple), the pushrod is not held in by anything. You need a retention cup (or something other devise) to make sure it doesn't fall out the back of the master cylinder. If the pushrod does come away from the master cylinder piston, the retention cup keeps it in line with the "dimple".

Pushrod Fall Out the Back = No Brakes = Injury or Death

On the Schwatrz chassis I'm getting it will have manual brakes with 13" wilwood brakes 6 piston front 4 piston rear. Jeff told me to he uses a master cylinder for a 70 corvette for this application. Cheap and works great. My be your answer.

13" wilwood brakes with 6 piston fixed front calipers and 4 piston fixed rear calipers is a lot larger caliper piston area than a big bore 2.75" metric caliper front and 7/8" wheel cylinders in the rear. Schwartz says to use a 1970 Corvette manual master cylinder with a 1” bore. That bore size is comparatively small compared to the brakes it supports. I am not saying their wrong. It just proves a point that you do not need a big master cylinder to have good manual brakes. Your master cylinder needs to be sized proportionately to the brakes you are using.

I have the same Wilwood brake set up on mine 13" - 6 Piston on front, 4 piston on rear, and I use the Wilwood 1¼" master.
It's not manual, I have a hydroboost, but it works real well.

Good, i feel confident the twin piston front and rears from strange will hold up with the Strange master cylinder with 1.25 bore and 1.550 stroke part #b3359. Mike
good thread here nice info

I ordered a Raybestos MC39166 7/8" bore master cylinder from Amazon for about $75, but it was taking 1 to 2 months for delivery, so I cancelled the order. I then went out to rockauto.com and order a Dorman unit M39166 for less than $45 with shipping.
quote]

Well the Dorman master cylinder from rockauto.com was also out of stock. Customer representative called me up to explain that there was a mistake in the system. He talked me into a Wagner unit MC101252. Roughly $65 with shipping. Hopefully it wil be here by the weekend so I can test this master, weather permitting.

Dave,I hope you get that master cylinder,I am really looking forward to how well it works out for you.
Guy

A day after I talk with the rockauto.com representative, I recieve my Wagner 7/8" bore 1978 Chevrolet Malibu manual brake master cylinder in the mail.

See something wrong with this picture? Reservior is on backwards. I will turn it around before i bench bleed it.



Made in the Good Ol' U. S. of A.



7/8" bore master cylinder piston with the pushrod "dimple"



I pushed in the piston with a brake pedal pushrod I had laying around. Travel was a little over an inch.

Weight of 7/8" Manual Brake Master Cylinder
3 lbs 5 1/8 ounce

Weight of Aluminum Step Bore S-10 Master (24mm / 1 1/4" step bore)
2 lbs 8 1/4 ounce

Only a little over a 3/4 of a pound difference.

I need to grind down some of the casting flash and shoot is with some aluminum or black colored paint to keep it looking fresh and not like a peice of rust after about a year.

Just an FYI.

The manual brake setup talked about in this thread uses the stock g-body manual brake configuration. The manual brake pin (stud), pictured in the pushrod linkage above, is pressed into a pre-drilled hole that is already in the stock vacuum power boosted pedal from the factory. There is no drilling involved with this setup.

That,s the master I used also works great

What is your brake setup (rotors, calipers, drums, wheel cylinder, etc.)?

Weight differences between Mater Cylinders.

Weight of Cast Iron 7/8" Manual Brake Master Cylinder
3 lbs 5 1/8 ounce

Weight of Aluminum Step Bore S-10 Master (24mm / 1 1/4" step bore)
2 lbs 8 1/4 ounce - difference of 12 7/8 ounces or a little over 3/4 lbs over the cast iron unit

Weight of an Aluminum Mopar / Strange style master cylinder
2 lbs 2 3/4 ounce - difference of 1 lb 2 3/8 ounces over the cast iron unit

Worked on the new 7/8" bore manual brake master cylinder for a 1978 malibu, Wagner part number MC101252.

I ground off the front casting "imperfections"



I ground off the bottom casting "imperfections"



I painted it with some aluminum color paint I had from a previous project.

Looking good Dave !!!
Guy

UPDATE:

I had trouble getting the brakes bled. I bench bled the system, but for some reason I couldn't get any pedal after I installed the system. I am going to use a bleeder kit to push brake fluid up to the master cylinder from the wheel cylinders and calipers. I will not be able to get to it until January 21st or 22nd, so stay tuned in until then.

Let me know if you have any questions.

Hey Dave,are you making any progress with your install ???
Guy

Haven't had the time to finish it up. I am looking at this weekend to get it completed. All I have to do is get the master cylinder bled and rebleed all the lines to make sure no air is in the system.

Hey Dave,just wondering how you are coming along with this project,keep us updated...
Guy