I have a 2002 Trailblazer Vortec 4200 4.2 L. I'm installing a hydrogen bubbler that uses a vacuum line to connect to the engine. I have tried connecting to the air intake just after the filter, but there is not enough vacuum for the bubbler to funtion. A quick test at idle and at 2k.

Can anyone tell me where the best place is to punch in a vacuum line connection that will work?

 

You could 'T' into the vacuum line that runs off the top of the throttle body. Best vacuum source will be from the intake or throttle body directly behind the throttle blade.

 

To go behind the throttle blade (intake manifold) I think I will need to take it to a shop.

Best I can tell, there isn't a vacuum line on the throttle body. Once past the throttle body in the intake manifold there is a large vacuum line that goes to the brakes. On top of the manifold is an electrical connection, probably a sensor of some type. The resonator has a small vac line for the fuel pressure.

I tried inserting a 1/4" vac connection between the resonator and the throttle body , it's not hardly two inches from the throttle blade. I used an npt 1/4" fitting. It didn't matter if idling or running 2-3k, the only time I had a vacuum was when I punched it. The fitting only extends into the air flow tube about 1/4". It's about a 3" dia. tube. Maybe the fitting needs to extend into the tube further to pick up a good vacuum.

I would rather not mess with the line going to the brakes, but some think that as long as it is sealed tight it is OK.

I was told that I'm going to need 20-25 psi.

Looking for any other good ideas for this vacuum pickup.