Gravity fed media blaster not working with long nozzle attached

[atikovi]

I'm using it to walnut blast the carbon on intake valves. It came with that short white nozzle and works fine with it. But when I replace that with an 8 inch nozzle for walnut blasting, I get just air coming out. I removed the black feed hose from the handle, and there is no suction when I pull the trigger. Actually I feel slight pressure. With the short nozzle installed there is good suction.

Any ideas? Could too much pressure cause this? Compressor regulator is set to 140 psi.

 

[rustedgoat]

Is there a difference in the nozzle orifice between the long and short one?

 

[atikovi]

What do you mean by orifice?

 

[GeoBruin]

What do you mean by orifice?

The diameter of the hole.

 

[atikovi]

Long one a little larger.

 

[PCustoms]

What is the long one off of?

 

[LS1-IROC]

With the long nozzle on there you are essentially pressurizing the gun body due to the air's inability to escape out of the long extension quick enough, which as you can imagine, kills any vacuum potential. This is why you feel air out of the suction port. You will need to downsize your air jet orifice size in order to make that extension work, or upsize the ID of your extension. There is a fine balance in suction blasting set-ups when you start adding extensions.

 

[atikovi]

OK that makes sense.