Loss of vacuum in brakes?

[West Texas Z]

Hey guys, I having some issues with my brakes. I just bought the car last year and I hardly drive it until recently when I started to finish it. I think it may be due to my Lunati Cam, could it be too agressive and be robbing my vacuum? I already bought a vacuum canister from Crane Cams and that didnt do a thing, I also bought a new master cylinder, new brake booster and now an electric vacuum pump. I'm hoping the E-pump will do it. (Havent installed it yet because its getting painted) What do you think?

Have any of you guys had this problem? Any help would be appreciated. Thanks.

[West Texas Z]

BTW, my cam is an Lunati cam .515/.515, duration 246/[email protected]'' 1.6 rockers


I dont know if that would help. lol Thanks again.

[badbu68]

What size motor and compression would help. Assuming that it's in a 350 with 10:1 compression, yeah, you're going to have a little less vacuum to operate PB at idle unless you put your idle pretty high.

[Apogee]

You've bought all of these vacuum accesories, maybe it's time to buy an inexpensive vacuum guage. That would tell you straight away whether you have adequate vacuum or not. Anything less than 11" Hg and you may as well not have vac assist, 11-14" Hg can be marginal, 14"+ is considered good in most circles.

I've never heard many good things about the electronic vac pumps, so I've never run one. I would prefer a manual setup.

[West Texas Z]

What size motor and compression would help. Assuming that it's in a 350 with 10:1 compression, yeah, you're going to have a little less vacuum to operate PB at idle unless you put your idle pretty high.

Sorry, I forgot to mention that. Yes its a 350.

Apogee, what kind of gauge are you talking about? like something I could tap into the lines like a fuel gauge or nitrous gauge or like one that you put in your dash? :hammer: :help!: :hmm:

[Apogee]

...Apogee, what kind of gauge are you talking bout? like something I could tap into the lines like a fuel gauge or nitrous gauge or like one that you put in your dash? :hammer: :help!: :hmm:

Yes, they make diagnostic tool versions (which is what I would get) and in-dash versions if you want...but I was thinking just something that you could check your manifold vacuum with at the port for the brake booster so that you know what you're working with. You can pay about $15 for a cheap one and go up from there, especially if your tools say "Snap-On" on them.

[GetMore]

Also, make sure the check valve is good. A vacuum cannister or vacuum pump will do nothing if it pulls air from the intake.

[6'9"Witha69]

Go Hydroboost or manual. I prefer manual. Set up properly you won't tell the diff between a vac. booster or not.

[West Texas Z]

Also, make sure the check valve is good. A vacuum cannister or vacuum pump will do nothing if it pulls air from the intake.


What do you mean? Isnt that were it supposed to be tapped to? (behind the carb on top of the intake manifold) Please tell me that its supposed to be there. :pat: I have a Edlebrock RPM performer by the way.


6'9"Witha69Go Hydroboost or manual. I prefer manual. Set up properly you won't tell the diff between a vac. booster or not.Yesterday 06:48 PM

Hydroboost is out of my budget. =(

[Apogee]

The check valve is the little plastic elbow that plugs directly into the vac booster on one side and the hose connects to the other leading to the base of the carb. If the check valve is bad, your booster would be very ineffective as it wouldn't maintain a vac against the diaphragm when the intake vac levels drop.

[West Texas Z]

The check valve is the little plastic elbow that plugs directly into the vac booster on one side and the hose connects to the other leading to the base of the carb. If the check valve is bad, your booster would be very ineffective as it wouldn't maintain a vac against the diaphragm when the intake vac levels drop.

See thats what I thought, behind the carb, but there is no spot for that on my carburator. I'm using a Holley 750 Double Pumper with a Proform Main Body. A race shop here tapped it to the intake manifold. Is that okay? Plus I've seen cars with it like that too. Thanks for all the help guys. I'm new to the V8 world. lol


Keep'em comming!

[GetMore]

You will get the vacuum from the manifold. That part is right.
The problem you might be having is that the check valve is after your vacuum cannister. You want the check valve before the cannister. If it's in the elbow as Apogee said then adding the cannister and pump are just a waste of time. the good news is that the solution is easy, simple, and cheap. You just need to install another check valve somewhere between the manifold and where the pump/cannister are "T"d in.

[West Texas Z]

You will get the vacuum from the manifold. That part is right.
The problem you might be having is that the check valve is after your vacuum cannister. You want the check valve before the cannister. If it's in the elbow as Apogee said then adding the cannister and pump are just a waste of time. the good news is that the solution is easy, simple, and cheap. You just need to install another check valve somewhere between the manifold and where the pump/cannister are "T"d in.

Awesome!!!! Thanks for the info. :twothumbs


You guys :headbang: