Engine/Transmission (1998.5 - 2002) Exhaust Brake Orifice Size???

[Turbo Tim 1]

Does anyone know what size orifice hole is in a Jacobs or other exhaust brakes. I have recently aquired a couple of Jacobs exhaust brakes for the Cummins ISC. They are designed to be mounted either directly to the turbo or inline with pipe mounts available from Jacobs. They are a 4 inch design so I figure it'll work perfect with my 4 inch exhaust, now I just have to plumb up some air supply and change the orifice size to work better with the little 5. 9.

 

[JFinke]

I belive the hole in my Pac Brake is a 5/8". Jake

 

[Turbo Tim 1]

Thanks for the info, the existing hole in these looks to be a little less than 1/2 inch and the picture of the other brakes I've seen for our engine seem to be smaller than that. I'm wondering if I need to make the hole smaller to be very effective.