hi all...
i got some question to ask .. :) sorry i m newbie here.

1. blow through.. can i just channel compressed air directly to the 'mouth' of the carb?

2. how bout those device using vacuum from the engine?
- most important.. the brake booster
- some other device.. like timing advance
- some part of the carb is using vacuum also...

its a myth in my mind.. how to source 'vacuum' for those device.. after we force induct our car, .. i curious

When you are "On boost" you aren't goping to be braking, when do do want to break you take your foot off the accelerator which will cause your biult up incoming air pressure (boost) to drop rapidly (within a second) and it will then be in the vacumm stage to help assist you brake.

Timing should be retarding when you increase your intake pressure otherwise detonation sets in so most turbo'd cars have thier dizzy locked at a certain timing, otherwise it's computer controlled.

Anything else that runs on vacumm in a turbo charged car is designed to only serve a purpose when your foot isn't on the accelerator like brake booster.... Etc

I hope I've answered your questions

Cheers
Damo

Blow through.
This is, apparently, how it's done. It places additional stress on gaskets, & some carbs will handle it better than others. I'm personally not a fan of this method, but there are plenty who are & who seem to have some success.

Vacuum Devices
The brake booster should have a one way valve in the line preventing boost from reaching the diaphragm. In order to apply the brake, you must take your foot from the throttle, which closes the throttle & produced manifold vacuum, so there should not be a problem here

Vacuum advance. If the boost is moderately low, then leave it connected. It only comes into play when you have some manifold vacuum in cruise mode, which is the only time that you want it to kick in anyway, & it is in the zero advance position when on boost. The only problem might be with higher boost pushing the hose off the fitting or perhaps damaging the diaphragm.

With some luck, some others will kick in with their personal experiences.

EDIT
Demojob, you got in while I was writing, so you must type faster than me. Good job.

wow.
thanks demojob amd dogdgeman.
now i understand the point..'

another thing i not so clear is,
i refer to tech section, someone mention building a 'box' for the carb, (with photo) for blow through setup
why need a box containing the carb, when we can just straight away connect to the mouth of the carb.. i just curious

If you pressurise the outside of the carb aswell it puts less one way pressure on the gaskets.

oic... so it put less stress on the gasket..