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Product Summary

Frame Position, Disc/Drum Brake System Type

  • Universal power brake upgrade that retains the brake pedal under the floor, automatic transmission only
  • Mounts to inside of frame rail or boxing plate to fit multiple vehicles, bracket mounts 2" off of frame
  • Features a 7" dual diaphragm brake booster, 1" bore Corvette style master cylinder w/ 1/2"-20 & 9/16"-18 IFF outlets, and 10-1/2" brake pedal assembly
  • Brake pedal is 1/2" steel plate and offers a 6 to 1 pedal ratio, round rubber pad included
  • From center of pedal pivot to front of mounting bracket measures 1.50"

Key Specs

MFG. Part #91664062
BrandSpeedway Motors

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Details

  • Universal bracket assembly converts under floor mount master cylinder applications to power brakes 
  • Power brake pedal assembly mounts to inside of frame rail or boxing plate
  • Retains through the floor pedal for period looks while improving braking safety
  • For automatic transmission applications only
  • Pedal ratio is 6:1 for ease of braking and works with all disc/drum setups
  • Corvette style cast iron master cylinder provides line access from either side of unit and includes port plugs
  • Master cylinder utilizes 1-inch bore with dual reservoirs for additional brake system safety w/ 1/2"-20 & 9/16"-18 IFF outlets
  • Dual diaphragm power brake boosters are compact and works with any engine providing at least 17 in/hg of vacuum

Power Brakes for Your Early Hot Rod

There is no denying that early braking systems on the cars we love to build, like Model Ts, Model As, and other pre-war rides, were rudimentary to say the least, and that is putting it lightly. These early mechanical brake systems may have been OK for the speeds of the time, but drop a hopped-up Flattie in it, or even more power via a small-block Chevy, and you are really asking for trouble when you must hit the “whoa” pedal after using too much of the “go” pedal.

Updating these classics to “juice” brakes (hydraulically actuated) has been the thing to do for decades and we are here to make that conversion easier for you. From disc and drum conversions, brake lines, proportioning valves, fittings, and more, Speedway Motors has everything you need to convert to hydraulic brakes on your pre-war hot rod, including this universal frame mount brake booster and master cylinder combo. These are the basis for your new hydraulically actuated braking system in your pre-war car and can easily be used to retain that period looking under floor master cylinder/pedal assemblies in ’40s and ’50s cars and trucks when under dash or engine compartment room prevents adding a power brake booster and relocating the master cylinder to the engine compartment firewall.

A Power Brake Conversion That Fits Most Early Hot Rods and Trucks

Adding power brakes to a pre-war hot rod is not always easy. Most of these original brake systems featured a mechanical brake system and early hydraulic conversions fitted the brake master cylinder under the floor, which did not always provide the correct leverage for optimal braking. Upgrading to power brakes using our universal brake booster and master cylinder with frame mount pedal assembly is a much better solution. The manual to power brake conversion retains the through the floor pedal assembly for period looks, but provides a solidly built mounting bracket, a compact power brake booster, and dual reservoir brake master cylinder that works with any open C-style or boxed frame member. The period look brake pedal passes through the floor and works with automatic transmission applications only. This kit works great in conjunction with a front disc brake upgrade as well.

Our frame mounted power brake booster and master cylinder combo kit features a zinc-plated 7-inch dual diaphragm power brake booster that provides more assist than the standard single diaphragm brake booster and yet is only 5-1/4-inch thick, allowing the brake booster and master cylinder combo to fit within your hot rod’s frame with ease. The power brake system works with engine vacuum of at least 17 in/hg or can be paired with an electric vacuum pump for those with aggressive cam profiles that produce insufficient vacuum. The power brake booster assembly includes mounting hardware for the booster and the master cylinder that mounts to it. Additionally, the booster includes an adjustable master cylinder pushrod and threaded pedal rod with lock nut for pedal height adjustment. The included brake booster check valve uses standard 3/8-inch brake booster vacuum hose for your engine’s vacuum source (carburetor base plate/spacer or intake runner vacuum tree).

The included Corvette-style brake master cylinder features a 1-inch bore with front and rear divided fluid circuits for the modern safety of a split braking system. Our master cylinder is designed for disc/drum applications with ports on both sides so that you can route your brake lines inboard or outboard however you wish for function and aesthetics. This brake master cylinder is ideal for a front disc brake upgrade solution. The ports are 1/2-20 inverted flare for the front circuit and 9/16-18 inverted flare for the rear circuit. Inverted flare plugs are included to block off the opposite side unused ports. For those crafting their own 3/16-inch brake lines we offer a master cylinder fitting kit to allow direct connection. If you choose to utilize pre-made lengths of 3/16 brake line our inverted flare adapters in 1/2-inch and 9/16-inch sizes will allow direct connection to our master cylinder without having to cut and flare brake lines.

Universal Mounting Solution Fits Any Frame Style

We have designed our frame mount under floor universal power brake kit to work with just about any frame configuration. As shipped the main mounting bracket will work with any stock or aftermarket rectangular boxed frame member, or an original C-channel type frame that has been boxed with steel plate. If your C-channel frame has not been boxed we provide an additional bracket attachment/extension that fits within the C-channel, providing a 2-1/4-inch mounting extension, that can be bolted or welded inside the C-channel to allow the main mounting bracket to attach to and sit at the proper spacing. We include all mounting hardware for both brackets, so if you do not own a welder installation takes nothing more than some careful measuring and a sharp drill bit! The brake pedal itself is a 6:1 pedal ratio and includes a 3-3/8-inch diameter classically styled round rubber brake pedal pad. Our kit makes a manual to power brake conversion easy, no matter the vehicle.

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Specifications

KEY SPECS
MFG. Part #91664062
BrandSpeedway Motors
GENERAL
PositionFrame
Brake System TypeDisc/Drum
Master Cylinder Mount TypeReverse
Pedals IncludedBrake
Master Cylinder Count1
Outlet CountTandem
Outlet Fitting1/2"-20 IFF
Outlet Fitting 29/16"-18 IFF
Master Cylinder Bore Size1 Inch
Master Cylinder MaterialCast Iron
FinishRaw
Reservoir TypeIntegral
Bolt Hole Pattern3.38" x 3.38"
Pedal Length10.5"
Pedal 1 Ratio6:1
Brake Booster IncludedYes
Balance BarNo
Hardware IncludedYes
Brake Pedal Rod IncludedYes
Sold in QuantityKit
Brake Booster TypeVacuum Diaphragm Dual
Brake Booster Diameter7 Inch