electric vacuum pump for power brakes and big cams

These never seem to work. Everyone I know who has one has been disappointed. I have one on my car and it would turn on but never turn off. My mechanic thinks he found a good solution by wiring the pump to the brake switch. The pump activates when you hit the brakes and turns itself off when you take your foot off the pedal. I will report back on its efficacy.

D.Hearne said:

Have you tried the brakes without the electric pump ? You didn't list what engine you have in your sig, only the parts it's got. My 331 was fine without a booster pump in my 89 Ranger. 331, Canfield heads, Ford Z303 cam w/1.7 rockers (228* @050 with a .587 lift hydro roller) 3x2 high rise dual plane intake.

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I have a 357W. I needed the pump when I had the flat tappet cam. The engine made enough vacuum to run the brakes at 1500 rpm and above but when slowing down and the revs dropped, the pedal became as hard as a rock and stopping in time became one of the most frightening things I ever experienced.

The electric vacuum pump solved that but it never ran as advertised. It was supposed to automatically turn itself on when the vac dropped below a certain amount and then shut itself off when the proper amount of vacuum was achieved. It turned on when needed just fine but once on, it never turned off. It was not designed to be constantly on. It would have failed in a short amount of time if it remained on all the time. I called to MP Brakes and they sent me new replacement check valves and switches but the pump still failed to switch off even after the new parts were installed.

I have since gone to a roller cam and the shop that made the cam says it has never had a problem with vacuum in the past with this cam profile. However, I already splashed out the money on the pump and my mechanic felt it would be a waste of money not to use it. When his tests showed that the pump was able to pull 20 inches of vacuum almost instantly, he decided to run it off the brake switch. We will see if it works. Who knows, maybe I won't ever need it.