Whenever a brake upgrade is made, usually incorporating discs brakes at the front or even all around, most builders will upgrade to power-assisted brakes. The number of kits available in the aftermarket makes installing vacuum power boosted brakes relatively simple in any number of applications, but of course this does rely on the engine providing enough vacuum to operate the booster. Using a high-performance motor, high-lift camshaft, or a supercharger can see vacuum levels that are marginal or insufficient to operate a vacuum booster, though using dual diaphragm or large diameter boosters can help.
While the Smeding 383 stroker small-block Chevy destined for our project '49 Chevy will provide enough vacuum for a booster, I also wanted to run the brake master cylinder under the floor, rather than on the firewall, and as the car will sit pretty low, I was concerned about a brake booster hanging down under the car. When I saw ABS Power Brake's Electric High Power master cylinder, and more specifically its compact size and the fact that it could be supplied with a bolt-in bracket to fit the '49 Chevy, it seemed like a no-brainer. ABS actually offers two different brackets, one for '47-51 cars and another longer version to fit '52-54 Chevy cars. Check their website for other applications as they can cover way more than just these models. The master cylinder itself (that is, without the bracket) measures just 10 inches long and 3 inches tall, and can be mounted on the firewall or on the frame, either remote fill or with attached reservoir, though add a couple more inches to the height if you opt for the non-remote fill versions. Whichever option you take, all are polished aluminum and there's a choice of styles if you go for the attached reservoir models.
An advantage of the electric system over a regular vacuum booster is that whereas if the engine cuts out with a vacuum booster you lose the power brakes and the pedal is very hard, if the power is lost to the electric version, you will still have at least 20 full power pedal pushes thanks to the accumulator in the system, and even then it will simply revert to regular non-assisted braking without the "hard pedal". Sounds like a win-win situation right? I thought so, so I trucked the Chevy over to ABS and followed along as Pedro installed the system in an afternoon. Now I just have to plumb the remainder of the system--yes we'll show you the correct way to go about that pleasurable job shortly--and very soon the Purple Pig will have both "go" and "whoa" again.
While it served me well when...
While it served me well when the '49 was stock, there's no way the stock '49 master cylinder was going to cut it with the new big rear drums and discs up front. A call to ABS Power Brake revealed they offer a couple of power brake options, both mounting in the stock location under the floor. The first task was to remove the original master cylinder, which also mounts the clutch pedal. As the '49 will run an automatic transmission, this is no longer required anyway. We'll need the brake pedal though, so this was removed and retained.
Using identical bracketry,...
Using identical bracketry, which mounts in the stock Chevy location, ABS can supply a regular vacuum power booster (top) or its Electric High Power master cylinder (bottom). The latter is available in under-floor fill or remote fill versions. I opted for the remote fill style for ease of maintenance.
Viewed from the side you can...
Viewed from the side you can see how the vacuum booster hangs down slightly from the bracket compared to the electric version, and while it is still tucked up in the chassis, on a very low car I prefer the peace of mind the compact electric version offers.
The ratio increase offered...
The ratio increase offered by this arm inside the bracket means pedal travel is kept minimal. The rod that connects to the pedal is adjustable to tune pedal height.
The electric pump is supplied...
The electric pump is supplied with a rubber mounting pad to insulate any small vibrations from the body or chassis, depending on where you choose to mount it.
The original brake pedal is...
The original brake pedal is re-used with the ABS bracket. Ours was sand-blasted which revealed a little pitting on the pivot, but it was still serviceable. The groove in the pivot performs two functions. It allows grease to be distributed from the Zerk fitting, as well as providing a location to enable the locking bolt to retain the pedal in the bracket. The extra holes in the bracket are for a clutch pedal, but these aren't required for our application.
The accumulator is mounted...
The accumulator is mounted in-line between the pump and the master cylinder, and allows the brake pedal to be applied 20 times without losing power assist, before returning to manual brakes, even with the engine off.
With the bracket installed...
With the bracket installed you can get a good idea of the location of the master cylinder, just a little rearward of the stock location.
The ABS bracket is designed...
The ABS bracket is designed to clear the stock crossmember, but our '49 uses a Walton Fabrication trans crossmember which required minimal clearancing to the ABS bracket (arrowed).
Once the master cylinder and...
Once the master cylinder and bracket were installed, and the brake pedal bolted to both the linkage and the pedal pad, the return spring was re-attached, though Pedro at ABS is of the opinion that it's probably no longer needed and may offer too much resistance.
In order to hook the system...
In order to hook the system up and show how it works, Pedro temporarily mounted the electric pump to the chassis rail next to the master cylinder, though I'll likely move it to the outside of the chassis once I have a firm idea where the exhaust will run. It should be mounted as close to the master cylinder as possible.
The accumulator was plumbed...
The accumulator was plumbed in the line from the pump to the master cylinder and will also be mounted on a permanent bracket once other component positions are finalized. The two brake lines coming from the master are for the front and rear brakes, and will be routed through a proportioning/combination valve.
Brake fluid is fed to the...
Brake fluid is fed to the reservoir on top of the master cylinder from the remote reservoir, and then to the electric pump in braided hose. From the pump it passes through high pressure steel lines to the accumulator and then on to the master cylinder.
Though an under-floor fill...
Though an under-floor fill is available, on the Chevy the door in the floor would almost be under the seat, plus I like the ease of a reservoir on the firewall, so I opted for this remote fill reservoir. As the remote reservoir is mounted above the rest of the brake system, ABS says there is no need to include residual valves. Our reservoir was mounted on the firewall, though you could also mount it inside the car.