AD Manual Brake Conversion on a 1980 El Camino

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malibudave

Apprentice
Mar 12, 2010
83
56
18
Houston, TX
#22
I purchased my second new master cylinder from rockauto.com a while back and just now had time to install it. The master cylinder is a Centric brand PN# 130.62005. It is a manual brake master cylinder for a g-body with a 7/8" bore. I installed it and bleed the brakes from back to front and got a good, firm pedal. I left the speedway motors recalled calipers installed, for now, to see how the system all worked together. I noticed, while I was under the car bleeding the brakes, I saw a lot of caliper defection as my dad pumped the brake pedal when the bleeder screws where closed.

How did it do? For the setup I have, it did very well. I could not lock up the front brakes, but the braking felt more confident than when I had the stock, 24mm bore power master cylinder . I felt, if I was driving this on the street a lot, I wouldn't have to anticipate my braking. I felt I could stop where I wanted to when I wanted to under normal street driving. As expected, the pedal stroke is longer than a power brake pedal.

What would I do different? I would find a better front caliper. I think I will try the Wilwood single piston, 2.75" bore, metric caliper. From my experience with the inspection of 2" bore, Wilwood, single piston, metric calipers, I think the 2.75" big bore Wilwood will have a larger piston that the CCP/Speedway Motors 2.75" big bore caliper. I just worry that any 7/8" bore master cylinder may not have the volume of brake fluid needed to make these work.
 
M

malibudave

Apprentice
Mar 12, 2010
83
56
18
Houston, TX
#23
Things I learned from this process.

*New master cylinders are hit or miss in functionality. My first new one I bought did not work, but it was a clearance item from rockauto.com. I ended up spending another $80 plus shipping for the Centric brand one that actually worked.
*The larger the caliper piston is the better the clamping force.
*Caliper deflection affects brake performance more that I thought.
*The smaller the bore of the master cylinder is the better the pressure to the caliper.
*But if the bore of the master cylinder is to small, it may not have enough fluid to fully compress the caliper piston.
*The diameter of the brake rotor also affects the performace of the brakes not only because of rotor area and heat dissipaton, but also a larger diameter rotor gives the brakes greater leverage. Just think of using a 6" long breaker bar instead of a 5.25" rachet to get a bolt loose. A longer bar will have a easier time getting the bolt loose. A 10.5" rotor has a 5.25" (half the rotor diameter) of "leverage". A 12" rotor has 6" of "leverage". Larger is better.
*They make brake pad designed for drag racers. They work better when cold and are for vehicles that do not use their brakes on a daily basis.
*Wilwood makes nice metric calipers.
 
M

malibudave

Apprentice
Mar 12, 2010
83
56
18
Houston, TX
#24
Here is a link to a person that carries new Proportioning Valves for Ford, GM, and Jeep.

http://proportionvalves.com/

Here is a link to a disc/drum PV for a g-body from the http://proportionvalves.com/ site.

http://www.carolinaclassictrucks.com/78 ... u-PV2.html

Here is a link to a disc/disc PV for a 2nd gen f-body that looks like it will work with g-body brake lines if you convert to rear disc brakes. Please call to confirm it will bolt in.

http://www.carolinaclassictrucks.com/79 ... M-PV4.html

MOPAR MASTER CYLINDER RETROFIT
I may have found a way to retrofit a 7/8” mopar (1993 Dodge Shadow) master to a g-body for manual brakes. I have not tested this yet to see if this works.

For the Front Brake port on the Proportion Valve:
Edelmann 258350 - Adapter-Standard To Dual Master Cylinder - 3/16" Tube - 3/8-24 Female Inverted Flare Seat x 1/2-20 Male Inverted Flare

For the Rear Brake Port on the Proportion Valve:
Edelmann 258340 - Adapter-Standard To Dual Master Cylinder - 3/16" Tube - 3/8-24 Female Inverted Flare Seat x 7/16-24 Male Inverted Flare

I don’t know the length of the brake lines from the proportion valve to the mopar master, but flared lines are less than $10 each from the auto parts stores. It should be about 2 to 3 foot of line. A coat hanger can be used to find the actual length needed.

If this setup works, this will be the cheapest way to get an aluminum master cylinder retrofitted to a g-body.

Let me know if you see any issues with what has been posted above.
 
M

malibudave

Apprentice
Mar 12, 2010
83
56
18
Houston, TX
#25
A Wilwood master cylinder will not work with the angle of a g-body firewall if the Wilwood master cylinder is bolted directly to the firewall. It physically bolts up, but there is a hole at the bottom of the master cylinder that regulates the fluid from one reservior to the other. When bolted directly to the firewall, the angle will let all the fluid run to the back reservior and the front reservior is left almost empty.

The Wilwood master should work on a TRZ or TNT adapter plates because these adapter plates correct the angle of the firewall and allows the master cylinder to sit horizontal (level) to the ground.
 
GuysMonteSS

GuysMonteSS

G-Body Guru
May 21, 2011
996
648
63
Kentville,Nova Scotia,Canada
#26
Hey Dave,I've been waiting to see if you were gonna do a follow up on your brake set up.I'm still wanting to do something to get rid of my brake booster for a cleaner underhood appearance.We have chatted on this or one of the other forums in the past about your manual brake conversions.I upgraded my front brakes a couple of years ago,and used a pair of slotted crossdrilled stock size rotors,USBrake oversize Metric calipers with the 2.75 in dia bore and Hawk HPS pads.This alone made a big difference over the stock brakes,but I only have enough vacuum for a couple of pumps of the pedal.Are you gonna be able to do more testing with the Centric master cylinder and the Speedway calipers and give a better evaluation ??
Please keep us updated.
Guy
 
M

malibudave

Apprentice
Mar 12, 2010
83
56
18
Houston, TX
#27
GuysMonteSS said:
Are you gonna be able to do more testing with the Centric master cylinder and the Speedway calipers and give a better evaluation ??
Please keep us updated.
Guy
My evaluation of the Centric MC and speedway big bore calipers is about 5 post up. I liked the Centric MC. I didn't like the Speedway big bore calipers because I could visually see a lot of deflection when the brake pedal was pressed with Centric MC. Because of a possible defect in the construction of these calipers, speedway motors sent me a set of CCP big bore calipers ( I did not install these calipers and I don't plan too). I don't know if the deflection is any different with the CCP versus the Speedway Motor brands, but visually the calipers are identical. This deflection has taken away some of the clamping force of the manual brake system and some braking "feel". I believe with a stiffer caliper, I would get a more substantial increase above the speedway calipers.

I am going to try the Wilwood big bore metric caliper. I hope when replacing the speedway calipers with the wilwood calipers I will get a noticable decrease in caliper deflection. My worry is that the Centric 7/8" bore master cylinder will not have enough brake fluid volume to support the increase piston size in the Wilwood caliper. If it doesn't have the volume there will be no brakes.

If the Wilwood big bore calipers cannot work with the Centric MC, then I will reduce the size of the piston and move to the Wilwood aluminum 2.38' bore metric caliper (Wilwood does not make a cast iron verson) and see how it performs against the speedway big bore caliper.

I feel that I finally got a good MC. I feel now that my manual brake system is on the right track. Like I said above, the car stopped predictable and I was comfortable with how the braking performed, but I think there is still some improvement that can happen because of caliper deflection.
 
M

malibudave

Apprentice
Mar 12, 2010
83
56
18
Houston, TX
#28
Just recieved my Wilwood 2.75" big bore calipers in today. These are very nice calipers, just like the Wilwood 2 inch metric calipers. The piston diameter measures 2.704 inches. On the underside of the caliper, there are ridges that bridge the piston side (inside) of the caliper to the wheel side (outside) of the caliper. These ridges are not present on any of the other calipers. These ridges should cut down of caliper deflection. The weight of each of the 2.75" calipers is 4 lbs 8.6 ounces with out the bleeder screw. I hope the 7/8" bore g-body manual brake master cylinder can handle the increase in volume these calipers may require.

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M

malibudave

Apprentice
Mar 12, 2010
83
56
18
Houston, TX
#29
Caliper Specs

Caliper............................Part Number........Advertised Bore Size.......Actual Piston Size..........Weight
Wilwood 2" Bore Caliper........PN 120-9333...................2.00"..........................1.981"................4lb 1.6oz
US Brake / AFCO Caliper.......PN 7241-9004..................2.50"..........................2.376"................6lb 4.7oz
CCP Big Bore Caliper............PN CP412526...................2.75"...........................2.565"................6lb 11.2oz
Wilwood 2.75" Bore Caliper....PN 120-8926...................2.75"...........................2.704"................4lb 8.6oz
 
M

malibudave

Apprentice
Mar 12, 2010
83
56
18
Houston, TX
#30
This week I put on the Wilwood big bore calipers. I got them bled and immediately had less pedal pressure when using the 7/8” G-Body manual brake master cylinder. The pedal almost went to the floor. I assume it is from the increased piston diameter over the Speedwaymotors.com “Big Bore” calipers (2.704” Wilwood v 2.565” Speedwaymotors/CCP) that I replaced. When driving with the Wilwood big bore calipers, I could pump the pedal 3 or 4 times and get the pressure I needed and would lock up the right rear tire and stop the car just like the other calipers. I suspect now I will need a 24mm bore G-body master cylinder (from a power, vacuum boosted G-body) and EE rated front pads to replace the FF rated front pads I have on the front now. The EE rated front pads have better “bite” when the rotor is colder. FF rated front pads have better “bite” when the rotor heats up. Since this is a street driven car, the EE rated pads should be a better choice and will match the rear EE rated shoes that are already on the car.
 

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