brake vacuum line on carb???

[ocbaud]

where does the vacuum line for the brake booster hook up on holley/demon carbs?

i believe the speed demon i am gonna get has 3 vacuum ports.

1 for pvc
1 for manifold vacuum
1 for ported vacuum.

[76HighSierra]

Usually, these carbs require that you run a "T" fitting, where your modulator valve line connects to the manifold. You will source your brake booster vacuum from there.

[ocbaud]

i already have the "t" fitting in there.

thats something else i was wondering about. how am i gonna be able to run that with the carb being so much longer than stock? wont it hit it?

[Destructo]

My friends demon extends over the rear vacuum port on his edelbrock performer, we just put a plug in it and ran his brakes off the carb, its probably not the best option, but so far it works, I think it should be coming off the manifold though, you get better signal that way. We put a vacuum resevoir on his to help the brakes out a bit too, but hes only running a xe262.

[TwinTurbo]

wherever you connect it, make sure you connect it to a port that sees full manifold pressure (since it's pressure lower than atmospheric, not a real vacuum), not venturi vacuum.

[76bonanza]

If you run a spacer under the carb will it raise it enuf to go over the vac fitings?

[Destructo]

I would think a 1" spacer should clear a short fitting, may have to cut some threads off to get it lower in the manifold. We can't put a spacer on my friends camaro because with the torker II it had before the performer and a adapter it would crunch a 2" tall air filter. But with OCbauds truck he should have plenty of clearance, i'm running a medium rise intake with a 4" tall filter and think I could run as much as a 6" filter.

[76bonanza]

How much longer is the demon than a regular holley?

I have a hollry now but plan on a road demon soon. just curious.

[Destructo]

The fuel bowls are slightly longer I think, do you have the 4160 holley? If so I would guess maybe 1/2-1" longer on each end. No gurantees on that though.

[Jonboy]

Doesn't the brake booster fitting screw into the bottom of the carb base on the Q-jet?

[Destructo]

Yeah, I believe so, mine is going straight to the manifold port though with nothing else tapping off of it. The port on my Q-Jet is just blocked off.

[ocbaud]

is the stock fitting for the brake booster the same size as the intake port?

also, i think i will only have to have the following hooked up:

full:
brake booster
tranny
heater vent thing
dizzy
pcv

nothing on ported.

is the pcv a different port? how am i gonna beable to hook all of those up if i only have the 2 ports on the carb?

[76HighSierra]

Originally posted by ocbaud
is the stock fitting for the brake booster the same size as the intake port?

also, i think i will only have to have the following hooked up:

full:
brake booster
tranny
heater vent thing
dizzy
pcv

nothing on ported.

is the pcv a different port? how am i gonna beable to hook all of those up if i only have the 2 ports on the carb?

Nope, the carb fitting is 1/4" NPT, while the intake fitting is 3/8" NPT. Hook your brakes, tranny and heater vent thingy up to the intake manifold fitting and the PCV to the large front port on the carb and the dizzy vacuum up to the timed port on the carb.