Mike Blanco

I have a LS motor with a decent size cam on this build. We replaced the OEM manifold with a Super Vic, with a 4150 style throttle body on top. I have been having a hard time getting the brakes to apply enough pressure. I took a vacuum reading this afternoon from the throttle body. At idle I only have 8" of vacuum. At 1500 rpm I have approx. 10" and I only get to 16" of vacuum at 2500 rpm. According to the Right Stuff, the folks whom I got the booster and MC setup from, said they want to have at least 16" of vacuum and a recommended 18". They recommended just getting an aux. electric vacuum pump.

EVP01

I am just trying to gather ideas and figure out whom I need to consult to try to get this resolved. I have also heard about a reservoir to work in conjunction with the vacuum pump as to not lose too much vacuum, but not sure what all I need for my street application. It seems like this is a pretty common problem, but did not think my cam setup would produce so little vacuum. Any help here is much appreciated?

Eredin

iTrader: (1)

I ran into the same problem, never assumed my cam was my root cause for what I had built. It pulls enough at throttle, but low RPM is in the low teens at best, 9" at idle. I opted for an aftermarket vacuum pump and solved that issue. Just make sure your vacuum lines are tight, easy to introduce a vacuum leak.

Mike Blanco

Do you just run a vacuum pump with no canister? Does the pump run all the time?

imma_stocker

iTrader: (19)

Since your motor still makes vac at X rpm you can probably run a vac canister. Hose from rear intake runs to canister then to booster. Pep Boys at 610 and Shepherd sells the moroso can.

Have you tried getting more vac from tuning?

farmington

iTrader: (14)

A canister would be the easiest and cheapest way to go. some of the cam companies sell a vacuum canister.
or you could toss the power brakes and just go manual. Personally I prefer the better feel of manual brakes.