Boost - Real or Imagined - 6.9 Banks Gen 1 w/ Isspro

[wildman7798]

I am trying to get an idea what I should see for boost from my 86 6.9 Gen 1 Banks less than 100k miles on engine and probably 50-60k on Banks w/ a C6 AT and 4.10 gears. I have the original Banks 3 gauge cluster on dash with I believe an Isspro boost gauge. When I got this all going a couple of weeks ago the boost gauge seemed to sit about 1 pound when running then under medium load and power up to around 3 to 5 pounds then under heavy accell up small grade I could see 7 pounds. That all seemed pretty normal and viable to me. I recently got rid of the old factory water seperator and mounted an aftermarket spin on adapter so I can run the Baldwin filters with the drain built into the filter. My brass fittings ended up hitting the cruise control unit so I had to do some creative tweaking and bending of the cruise unit to make clearance. Of course pushing, pulling and generally working over all the vacuum lines on the cruise. Up and running again but my boost reading seems a little different now. When pulling away from a stop my boost drops down initially like from 1 to zero - then starts to go up.- Like you would see an auto vacuum gauge do. When the C6 shifts under hard acceleration the boost gauge drops down and then back up like from 5 to 4 then back to 5 rapidly.. sort of bounces. It just seems different than before this fuel filter work was done. Is there a good way to test all this - I have a manual vacuum pump and a vacuum gauge. Not sure if I cracked a line or fitting with my agressive bracket work or if the gauge is bad or it is my imagination. The cruise seems to work as normal. What is the expected boost range for a good. stock 6.9 with a Banks Gen 1? Thanks.

 

[icanfixall]

So being a 1st gen turbo I'm thinking its not a wastegated unit. Then 6 or 7 is about what you should see. Any exhaust leaks will kill a turbo boost. So look for sooty areas around the exhaust manifolds and all the way to the turbo hot side. Any soot at joints past the turbo hot wheel are not a problem for boost. Also check the cold side of the turbo and the intake hat seal. any leaks there wil show up as oily places. Thats a boost leak and it will effect the boost too.