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Tech Talk with Master Power Brakes

Fixing a Power Brake Problem Using An Electric Vacuum Pump

Posted by mpbrakes1 on Feb 16, 2017 10:32:50 AM

One of the greater luxuries for classic musclecars with nose-heavy big blocks is power brakes. While some would rather have the full feedback of a manual brake pedal, the soft touch of a power booster-assisted master cylinder is sometimes more of a blessing than a luxury.

But we’re gearheads, and we have a penchant for making big power with our big blocks, and that often means bigger cams, headers, big carbs, and lots of noise from under the hood. However, the drawback to having a bigger cam is that your engine will get stingy with vacuum. Master Power Brakes has a new Electric Vacuum Pump Kit (PN AC9001K) that plays nicely with big cams because it provides that much needed vacuum for the brake booster, but it does so independently of any manifold vacuum source.

This 440ci has a bit of a radical cam, and that meant a vacuum canister was needed for the power brakes. But Master Power has a better solution, and it takes up far less room.

One Big Air Pump

Electric Vacuum Pump Kit

Part Number: AC9001K
Included in Kit:

  • Electric vacuum pump with Silent Drive Technology
  • 10-feet of premium vacuum hose
  • Laser cut steel mounting bracket with rubber shock absorbers
  • OEM quality wiring harness with in-line relay and fuse
  • Mounting template
  • Wiring Diagram

Your engine is a large air pump, and to pump that air it needs to pull it in through the intake valves where the piston can suck in as much air as it can with the fuel mixture. On the next stroke of the of the crankshaft, the piston compresses the air and fuel so the ignition can explode that mixture and send it out through the opening exhaust valve.

One of the best ways to pull in more air and fuel is to open the valve further, and that means a bigger cam. This combination equates to more power, as well as a bigger smile on the nut behind the wheel. But the drawback to the bigger cam is that your combustion chamber has first dibs on all that air being sucked in, and anything external to that chamber, such as your brake vacuum booster, plays second fiddle to the requirements of your thumpstick.

Bigger cams steal that incoming charge of air and that leaves your power brakes lacking the boost needed from the engine’s vacuum levels. Master Power’s electric vacuum pump is a small, efficient pump that creates the vacuum needed to add that boost to a power brake system, leaving the camshaft to pull all the air it needs.

Master Power’s vacuum pump kit includes everything needed to complete the installation, with OE style components and connectors.

Five Questions With Master Power Brakes

We reached out to Mark Chichester, Vice President of Master Power Brakes, to find out more about this new, compact and powerful vacuum pump.
Street Muscle: What is the life expectancy of your vacuum pump?
Mark Chichester: Our pump is used in the OE new car world. In fact, it is used in an electric vehicle. I say that to enforce the fact that the pump will probably outlast any vehicle it is put on, we use the same OE sourced motor.
SM: How much vacuum does the pump produce?
MC: Any brake booster in the world requires 18-inches of vacuum to operate at peak efficiency. Therefore, the pump turns on when it reaches a vacuum level of 18-inches, and it shuts off as soon as it gets to 23-inches of vacuum. This takes about 4-1/2 seconds compared to ten seconds from our previous version and others on the market. This means that there is no chance of the pedal becoming hard in a stop and go driving situation.

The 1970 Plymouth has a mighty thump, and it was time to get some vacuum back for the brake booster.

SM: Should this pump only be used for brake boosters, or are there other applications?
MC: It could be used in other applications although we have not tried it. We have had people tap into the system to run various vacuum functions in the vehicle such as vacuum headlights and heater doors. We haven’t heard anyone say yet that it doesn’t work.
SM: While driving and not using the brakes, should the pump cycle on and off regularly?
MC: When not on the brakes, the pump should be dead quiet and not running. If it does run for an extended period of time, or the pump cycles on and off without using the brakes, that is a sure sign of a vacuum leak.
SM: Do you have sound readings (decibels) to compare to?
MC: Our old pump and most any piston driven pump measures approximately 85 decibels. Our new rotary vane pump measures approximately 56 decibels. These were taken with a sound meter app on my phone, so by no means are they scientific but they at least illustrate how much quieter one is compared to the other.

Full instructions and mounting templates are included with the kit.

Pump Installation And Mounting Choices

We found a prime candidate for the Master Power vacuum pump when we visited Stephen Poe, of Laverne, California. Stephen is no stranger to big-block Mopars, and we’ve featured his prior vehicle, a 1967 Plymouth Barracuda with a 572-inch Hemi. This time around, he ran into an issue with his new car – a 1970 Plymouth ‘Cuda with a 440ci mill with a bit of a radical cam.

“The pump can be mounted as far away as the trunk, or installed in the engine compartment without any trouble.” -Mark Chichester, Master Power Brakes

The problem he ran into was just as we described above: his cam was hogging all the vacuum, and his power brakes suffered from the remnants of whatever vacuum was left over. That made Stephen a perfect candidate for the Master Power vacuum pump.

Chichester said, “The pump can be mounted as far away as the trunk, or installed in the engine compartment without any trouble. The only recommendation is to keep the relay and the fuse block in the dry.” He also reminded us that the pump should be kept away from the elements, such as water splashed up from driving in wet conditions, and should also be kept away from any direct heat source.

The pump ended up being quiet enough that it was mounted inside the car where there was a good spot for it, just behind the firewall.

Because this pump is so quiet – and because the engine compartment is packed with big-block power – Stephen chose to mount his vacuum pump inside the car, up under the dashboard. Wiring the kit was simple enough, with all the wiring and connectors, as well as the relay and switch, included with the vacuum pump kit.

With many vacuum pumps, the noise they make would make you want to mount it as far away as possible, but after installing the pump Stephen felt that what little noise it made is completely livable inside the cabin. We drove the car around the block and the pump fired up and reached vacuum within seconds, and was off again. Brake pedal effort is again minimal, and full braking effect has returned now that the pump has been installed.





Top: The hose was run through the firewall, and mounted directly to the booster. The wiring came through the same grommet and was connected to the battery.

Bottom: First test on the vacuum pump resulted in about 21-inches of vacuum in just seconds. It's a clean, simple install and now the booster isn't battling the cam for vacuum.

Electrical connections are simple: a ground and power wire directly to a battery source, and an ignition source for the relay and switch. The vacuum hose connects from the pump directly to the brake vacuum booster with a supplied hose, and anyone with minimal electrical abilities can perform the install.
We recommend planning out the installation, making sure of any mounting location issues you might encounter, and drilling any holes necessary for wiring or for the hose itself if mounted inside, like Stephen did. He was able to find an existing hole in the firewall that he could use to route the hose, and wiring went directly to the fuse block behind the dash.

Rosie, supervising the installation, approves of the Master Power Electric Vacuum Pump Kit. That aluminum canister looked nice, but it had to go.

Upon first connecting the electrical, vacuum was reached in mere seconds, and the pump was off. Master Power created a solution for big cam engines with power brakes, and did so in a quiet and compact package with its Electric Vacuum Pump Kit.

You can find it on the Master Power Brakes website, along with disc brake upgrades from OE style to multiple piston calipers from both front and rear of nearly any classic car or truck. Chichester added, “The pump is efficient enough to not require any additional vacuum from the engine making this a true standalone solution to a vacuum problem.”

Editorial credit – Michael Harding, Street Muscle Magazine / Power Auto Media. Feb. 7, 2017

Topics: aftermarket vacuum pump, How To Series, classic car electric vacuum pump

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