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malibudave 01-06-2012 05:11 AM

Manual Brake Conversion
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 ˝ 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.

For the manual brake setup, I am going to test the original strait bore aluminum master cylinder with 24mm bore.

malibudave 01-06-2012 05:13 AM

The manual brake conversion went well when using the manual brake hole that is already predrilled in the factory vacuum booster power brake pedal. 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:

malibudave 01-06-2012 05:13 AM

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.

malibudave 01-06-2012 05:15 AM

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

malibudave 01-06-2012 05:16 AM

I ordered a Raybestos MC39166 unit 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 and order a Dorman unit M39166 for less than $45 with shipping.

Well the Dorman master cylinder from 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.

malibudave 01-06-2012 05:17 AM

A day after I talk with the 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.

nowukno 01-06-2012 05:19 AM

Very good thread....:woott: The 7/8 bore master cylinder should do wonders for the manual brakes and give you better pedal feel.

malibudave 01-06-2012 06:01 AM


Originally Posted by nowukno (Post 24673)
Very good thread....:woott: The 7/8 bore master cylinder should do wonders for the manual brakes and give you better pedal feel.

That is what I am hoping for. I will have an update hopefully next week.

Poltergeist 01-06-2012 07:27 AM

Nice write up!

nowukno 01-06-2012 07:35 AM

I run manual 4 wheel disc on my El Camino, the smaller the MC bore the better. yes,please keep us posted..

malibudave 01-06-2012 09:10 AM


Originally Posted by nowukno (Post 24681)
I run manual 4 wheel disc on my El Camino, the smaller the MC bore the better. yes,please keep us posted..

Are you are still running a Strange or Mopar master?

If so, what bore size is it?


nowukno 01-06-2012 09:29 AM

Im running the wilwood master 7/8 bore

malibudave 01-08-2012 08:03 AM

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

malibudave 01-08-2012 08:05 AM

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.

malibudave 01-08-2012 08:55 AM


Originally Posted by nowukno (Post 24684)
Im running the wilwood master 7/8 bore

Do you know how much that Wilwood master cylinder weighs?

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