Manual Brake Conversion - G-BODY
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.
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:
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.
Assembled Top View
Assembled Side View
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 rockauto.com and order a Dorman unit M39166 for less than $45 with shipping.
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.
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 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
I need to grind down some of the casting flash and shoot is with some aluminum color or black paint to keep it looking fresh and not like a peice of rust after about a year.
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.
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.
Thanks for posting this. Looks really good w/o that booster.
I have an '80 Malibu wagon I'd like to do this to, where did the adapter plate on the firewall come from? Any chance you could show the dimensions or a blueprint of it?
Is the adjustable pushrod a necessity if using an OEM manual master cylinder?
The disign in the link is based on the original design.
My design "tightens up" the specs in the link and takes out the "slop". There is no adjustment needed in the plate I designed. It bolts to the firewall and aligns the master cylinder to the push rod attached to the pedal. My design also has an integral pushrod retainer (keeps the pushrod from falling out the back of the master cylinder).
An adjustable pushrod is not nessesary, but it gives a lot of extra adjustment and it will take a lot less time to get your manual brake pedal set up and working correctly.
Let me know if you have any additional questions.
Purchased an additional new 7/8" bore master cylinder just in case the older new one I bought doesn't work like it is suppose to when I install it on the El Camino. When I was bench bleeding the older, new one, the front port for the rear brakes would suck the fluid back into the master cylinder after the piston was released. The rear port for the front brakes didn't have this issue.
Is this normal? I don't know, but I will find out from the new master cylinder that I bought.
I also baught a rebuilt, aluminum master cylinder, with a 1" bore, from a 1979 Buick Riviera with the optional rear disc brakes. I did this because the reservior is larger, it can be retro fitted to the 7/8" bore manual brake master cylinder, and it matched the angle of the firewall. You don't need it for rear drum brakes, but I like the extra fluid capacity.
Here is a link to a person that carries new Proportioning Valves for Ford, GM, and Jeep.
Brake Proportioning Valves | Unbeatable Prices on Prop Valves with Carolina Classic Trucks
Here is a link to a disc/drum PV for a g-body from the Brake Proportioning Valves | Unbeatable Prices on Prop Valves with Carolina Classic Trucks site.
1978-1986 Chevy Malibu Front Disc/Rear Drums Proportioning Valve at Carolina Classic Trucks
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.
1979-81 Pontiac Trans Am Front Disc/Rear Disc Proportioning Valve at Carolina Classic Trucks
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.
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.
I have purchased 3 different metric calipers for comparison:
**CCP big bore 2.75" bore (2.565" piston diameter) metric cast iron caliper – WEIGHT 6 lbs 11.2 oz bare with slider bushings installed
**US Brake standard bore 2.5" bore (2.376" piston diamter) metric cast iron caliper- WEIGHT 6 lbs 4.7 oz bare with slider busings installed
**Wilwood small bore 2.0" bore (1.981" piston diameter) metric cast iron caliper - WEIGHT 4 lbs 1.7 oz bare with NO SLIDER BUSHINGS INSTALLED.
A while back I purchased NEW the $59.95 each, big bore calipers from speedwaymotors.com. There was some manufacturing issues or problems with these calipers and they sent me replacement calipers. The replacement calipers are NEW CCP big bore metric calipers. PN CP412526. Online, these are the same price of $59.95 each from classicperform.com. They look exactly the same except for the paint on the calipers. The originals where painted/powder coated silver. These are painted/powder coated black. The caliper housing, compared the standard bore US Brake 2.5” calipers and 2.0" Wilwood calipers, are a different casting. The piston looks to be stainless steel and comes with a dust boot installed. The piston diameter is 2.565" in diameter. These calipers came loaded with pads, slider bolts/pins, and hose fittings. You should be able to bolt these to your car, bleed the brakes, and drive. The piston cylinder side of the caliper is roughly the same size as the as the standard 2.5” bore caliper.
I recently purchased NEW, US Brake/Afco branded 2.5” standard bore metric calipers. They are $45 to $50 each online. The casting is not painted or powder coated. They come in a right PN 7241-9003 and a left caliper PN 7241-9004. They cannot be interchanged from side to side. The piston looks to be a cast steel/iron, unlike the CCP 2.75” and Wilwood 2.0” bore calipers. They are also 2.376" in diameter which matches stock advertised piston/bore sizes. The casting looks to be a stock casting and comes with a dust boot installed. It has all the markings of a stock calipers. This caliper came unloaded with no pads, slider bolts/pins, and hose fittings. It does come with the bleeder screws and bushing inserts for the slider bolts/pins. You will have to reuse your slider pins from your stock calipers and hose fittings. You will need to purchase new pads or reuse the ones you have on your car.
I also recently purchased NEW, Wilwood 2.0” small bore metric calipers. PN 120-9333. The price is round $80 each online. It is also a different casting from the other two. Visually the casting looks better and it looks to come with a stainless steel piston that is 1.981" in diameter. The casting comes bare with no paint or powder coating and they can be interchanged from the right and left hand side of the car. The piston cylinder portion of the caliper is physically smaller than the other two because of the reduced size of the piston. The piston bore and stainless steel piston look to have a better, tighter fit. The clearance is so tight there is no dust boot installed around the piston like the 2.75” and 2.5” bore caliper above. These calipers only come with a bleeder screw. It does not come with any other hardware. You will have to supply the slider bolts/pins, slider bolt/pin bushing inserts (I need to make sure this is possible), brake pads, and hydraulic hose fittings. All hardware should be able to transfer over from your original caliper. Please refer to this web page for more details. http://www.wilwood.com/PDF/Flyers/fl176.pdf
Out of the three calipers above, I was most impressed with the Wilwood calipers. These calipers have a very clean casting that weigh at least 2 lbs less than the other two calipers. The Wilwood website list a 2.75” bore version also that weighs just 5 more ounces than the Wilwood 2.0” bore versions (4lb 6.4oz v 4lb 1.6oz). These Wilwood iron calipers weigh roughly 1lb more than the Willwood comparable aluminum metric caliper with the 2.38” bore (4lb 6.4oz v 4lb 1.6oz v 3lb 6.4oz). I also suspect that the piston to bore clearances are just as tight as their 2.0" verson which will give the 2.75" version of the Wilwood caliper a larger piston that that of the CCP version. It theory this gives more clamping force.
Pics of the CCP 2.75" Big Bore Metric Caliper
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