If you have been following my Bendix [1] Self-Energizing Series, this 51 Chevy 2 door Fleetline is the third and final car in the series. The principles of the Bendix [1] system have been covered in previous issues and a comparison between Chevy's Huck 1936-1950 to Chevys new-for-51 Bendix [1] systems can be viewed by visiting our Archives section at www.southernwheels.com.
The linings on all '51 Chevy cars are 2"front and 1 3/4"rear linings x 11"drums. The linings were originally bonded, and used with a single reservoir 1bore master cylinder. Conventional Dot3 brake fluid was used. Our cars problem was that only the left front brake worked. We had bled all of the wheel cylinders and fluid came out of the front two only. Fortunately, our lift was free, so we thought that while the brakes were apart, it would be a good time to do a complete brake rebuild, scrape, clean and lightly undercoat the underside of the car. After inspection it was obvious that everything in the braking system would have to be replaced. All brake lines were checked, disconnected, blown out with air, junction blocks removed and cleaned out with brake cleaner and the brass polished, the wheel cylinders were replaced with new ones, mounting bolts cleaned and painted, new crush washers used at the pipe-to-wheel cylinder connection as well. Most new crush washers are hard and flat on both sides. I wanted the old style that were soft and flat on one side and slightly arched on the other side, and I found multiple sizes of these at Pegasus Auto Racing Supplies.*
As the braking system was dismantled, we took pictures and notes on everything. Sometimes brake drums can become stuck, but all of ours came off easily. We noted that on the left and right back brake drums, there were three Tinnerman nuts on each rear drum. These were used at the factory to hold the rear drums on as the car was being assembled (they are push on speed nuts). The front drums were held on with the hub nut and cotter pin before the wheels went on as the car moved down the assembly line. When we removed the drums, we didnt see anything unusual, just rust and muck. The return springs were on rightyellow to the secondary side (it has the strongest pull). Most new sets dont color code except for some muscle car sets. We removed the front bearings and marked which side they went on, and hand cleaned them (we never wash and blow with air spinning them dry; this scores the bearings), new seals were bought and installed. I bought four new brake drums (front and rear drums are the same). The rear drums just push on the wheel studs, but the front hubs are riveted to the drums with three large rivets. These rivets must be drilled out and hubs removed to put the hubs on the new drums. I didnt have to do this, however, because my original drums were turnable. These originals were really made well, heavy cast iron that have many resurfacings in them. They run true and dont wobble. USAcant beat it! When I had them turned, the machinist that turned them went inward beyond the surface of the lining so there was plenty of lining surface, lessening the chance of brake grabbing. I have such a respect for people who know their craft and do the details that make the project work well.
The Master Cylinder was a little more difficult than the drums and shoes had been. It is mounted on the left side and fluid is added from top side by pulling back the mat/carpet, removing a large rubber plug and filling the master cylinder, located under the drivers feet. It mounts to the frame with two bolts, one long and one short. The unusual thing about these is that the clutch and brake shafts go through bushings at the front of the master cylinder. When the two shafts are in place, there is a brake/clutch shaft lock pin to keep the brake shaft and clutch shafts in place. It is inserted through a grease hole in the front of the master cylinder. These are available new at *Chevs of the 40s part #127875A for 216 manuals (1940-54). The early 1951's (my car) had a pipe plug to cover the grease hole. In late 1951, they were replaced with grease zert.
When installing a new master cylinder, it is best to lay the old/new side by side because you will need parts from the old one: 1) a brass junction block for (2) brake lines, and an eccentric bolt on the front of the old master cylinder that will have to be put on the new one). Also, there is a pipe plug thats on the left side that the original did not have. The supplied pipe plug (new one) is not tapered as most pipe plugs are. The new ones are like a screwthey just keep screwing in! We replaced this with a 1/8tapered brass one. It stopped and only went in about half of its threads, and sealed well.
In our underside cleanup, we cleaned the backing plates using a die grinder with a wire wheel. The plates were stripped, metal-prepped, primed and painted with cast. When spraying cast from a can, keep shaking it or it will come out spotty.
Return Springs. I bought new return springs but I wanted to test their return pull. I have a scale to do this, that goes to a 100 pound pullway more than a '51 Chevy return spring would require. I put on my goggles, put one end of the spring in a vise and attached the other end to the scale and pulled straight back. The secondary (yellow) is the stronger spring and it tested 68 pounds. The primary spring tested at 60 pounds. This is about right. The new springs both tested at 65 pounds. I re-used the old ones.
The brake star adjusters were rusty but I found some NOS GM ones (hard to find). They turn like butter.
The '51 brakes are now ready to assemble. 1951 was the first year for Chevrolet to have self-servo Bendix [1] brakes. From 1936 to 1950 they had Huckhydraulic brakes. Previous to that, they were mechanical.
This will be the conclusion of our several-part series on the Bendix [1] systems. I covered a 1946 Packard Custom Super 8 (356), a 1951 Packard Mayfair hardtop (250) and this 1951 Chevy Fleetline 2 door (fastback) manual shift (see the Archivessection of www.southernwheels.com for previous articles). The last 1951 Chevy article was the May 2018 issue which ended with putting on the master cylinder. With the master cylinder, new brake lines, wheel cylinders installed, it was time to put on the shoes. I bought the brake shoes a few years ago, and they are the originalmaterial and bondedtype as the originals were. I saved the old ones that came off of the car and purchased a complete set of NORS linings for later brake work. The Chevy had its original Chardened steel hold down clips, but they had lost their spring,and were loose when I removed the shoes. I replaced them with the round spring type. The shoes were assembled on the bench by connecting them at the bottom with the star adjuster with the spring above. This holds the shoes together and makes them much easier to put on the car (short shoe primary to the front). I put them over the backing plate, pulling them apart at the top clamping them into the wheel cylinder thrust rods. On the rear shoes there is a cross plate with a spring and a thin mechanical arm that swings and attaches with one bolt and lock nut that activates the emergency brake operated by a cable that is controlled by a pull/push handle under the dash. With the shoes together, they become attached to the backing plates with two hold down spring assemblies, one on each shoe that consist of a spring, two cups with holes through the centers with the outsidecup holes slotted for the hold down pin. The pin has a flat end and is inserted from the rear side of the backing plate through the hole in the shoe, inside cup, spring, and locked down on the outside cup by turning the pin until it fits into a groove in the outside cup. We usually lock them in place using needle nose pliers. On these lock down springs, the cups push into the spring and stay together, allowing them to go on as one piece. The shoes were now hanging and could be easily centered on the backing plate bosses. You can feel it when they are centered. There is a clickand you can see that there is equal distance on each side. We made sure at this point that everything was ready for the brake drums to go on, checking that the new star adjusters were in the correct position. They must be turned so that the star wheelis aligned with the adjuster slot in the backing plate. The return springs at the top were the last thing to go on. Most sets that are made now are not color-coded, but the originals were orange for the primary shoe and yellow for the secondary shoe. The yellow spring has a few more pounds of pull due to the extra thrust on the secondary shoe. I always do a spring test to show the pull of each spring (see May 2018 article). There should be 3-4 pounds greater pull by the secondary spring. We put just a little red high-temp grease on the backing plate bossesnot on the liningsand a little on the emergency brake pivots.
Brake Drums: We bought all four new Bendix brake drums although only two of the new ones were used, and they were used on the rear. The fronts are riveted on to the hub and the rivets have to be drilled out and the new drum put on the hub assembly. Our old front drums were turned, bearings packed, and new seals installed. On drum brakes, use old style brown axle grease, not new red high temp grease as used on disk brake systems. The front drums pushed right on smoothly, then the outer bearing, race, washer and nut, the locking nut was tightened until the wheel wouldnt turn, then backed off until the first cotter pin hole was visible. A cotter pin was inserted and bent over and the grease cup went on.
On the rear new drums, things were a little different. The drum went on fine, but didnt lie flat on the axle. When we pushed down on one side, the other side came up. The axle had been cleaned, no burrs, the trouble was in the new drums. The center hub hole was just a millimeter too small! We removed the back drums and, using a die grinder and burr, I went around and around, cutting just a little off of the center hole with each 360-degree pass, test-fitting about every three passes, then reinstalled the rear drums. They now lay flat across the axle. We removed them again and cleaned up the rough cut edge with 220 grit sand paper, then wiped on a little grease around the hole, and a little on the rears paper hub gasket (red grease) to help prevent a stuck-ondrum in the future, and pushed on the drums. Now with all four drums on, it was time to bleed the brakes. The master cylinder was filled with Dot 3 and had been bench bled. Now we needed to get fluid to the wheel cylinders. I got in the car with the master cylinder cap off and armed with a fresh bottle of Dot 3, while Jason raised the lift and using the old pump the pedalholdbleed and releasemethod, we bled all four brakes, starting with the furthest wheel cylinder, right rear, then left rear, right front, left front, keeping the master cylinder full at all times, then repeated the process until all air bubbles were out of the system and only clear fluid came out of each bleeder. We are going to bleed again using our new reverse bleeding tool, where the master cylinder cap is removed, master cylinder fluid level is kept to about half-full and using the bleeder tool at each wheel cylinder, fluid is pushed up into the master cylinder, pushing the bubbles out. Well let you know how it works. It eliminates the need to make multiple master cylinder caps on these old cars that dont have plastic caps.
Now it was time for shoe adjustment. Using a brake spoon, each adjuster was clicked until the wheel locked down, then backed off a few clicks until each wheel could spin 1 1/4 turns freely. This gave us about ¾ pedal. This process differed from the Packards, where there is a slot in the drums where a feeler gauge is inserted, and you adjust the shoes to a specified clearance. Both ways work well. Now the newly-painted black rims with new 670/15 Firestone gum dippedblackwall tires with restored blue bowtie hub caps went on. Down with the lift, out with the Chevy and on the road for a test drive. The car now steered so easy with the correct tires and had an excellent brake pedal. The 51 went back into the garage for a little more tweaking on other things, then will go to the upholstery shop for a front seat recovering in the correct gray pinstripe and solid gray cloth material. The brakes took a long time, but they work well and we have the satisfaction of knowing that every attention to detail was done. I hope you enjoyed this series on Bendix [1] brakes. Enjoy your cars and keep em driving!