Turboing update

[TomC]

Well I think I finally got the turboing job done.  Briefly for those that don't know, I have an AMGeneral 40ft transit with a 8V-71 and V730 Allison.  I weigh 34,750lb with the towed.  While I didn't mind the slowness going up hills (32mph on a 6% grade-about like the trucks), when I got up to 7000ft (in Flagstaff, AZ) it smoked and my power was down with worse fuel mileage.  So with that I decided to turbo the engine.  Since it had about 15,000 miles on an overhaul, should be alright.  I had Don Fairchild in Bakersfield do the work.  What was done-first pull the engine/transmission cradle.  Then Don popped one of the pistons out to see what rings I had, luckily the right ones.  Then he installed 9G75 injectors (up from N65), rebuild the blower and added the bypass valve, installed the turbo and plumbed it to the air to air intercooler that I had custom made and installed myself.  Drove great the first time, but had to enlarge the radiator from a 5 row straight fin to 6 row serpentine fin core, enlarge the air cleaner from a 6" to a 7", and just finished today installing a 5" muffler for turbo engines.  While I was at it had the transmission overhauled.
I installed a King cruise control also.  So today took it for a drive and no more smoke at full throttle (which you don't have to do very often anymore) and the cruise control worked great! 
I can't tell you enough how the turbo and air to air intercooler woke up the 8V-71.  I highly recommend anyone thinking of chucking their 8V-71 for a 6V or 8V-92 reconsider.  Properly built, you can get the same power from a 71 as the 92 based on both using 90 injectors.
I went from 300hp and 800lb/ft torque to 375hp and 1125lb/ft torque.  The difference is where before I would go 32mph up a 6% grade, now do 42mph.  And most of the small hills, it doesn't even need to down shift.  One drawback, I spent $17,000 on the complete turboing/transmission project.  But now have fresh everything in the engine compartment ready for the next 10 years!  Good Luck, TomC

[lostagain]

Sounds great Tom C!! My project ( turboing my 4-71 in Courier 96) is almost done. I am just waiting for a turbo flange that mounts on the exhaust side of the turbine, then I can complete the exhaust installation. I'll post on the results after my first test drive. I haven't gone for the intercooler yet. It sounds like a good idea, and that might be my next project...
What is a "bypass valve?"

JC

[TomC]

Bypass valve on the blower- in the most modern version with turbocharging, Detroit installed a bypass valve and passage that allowed some of the turbo pressure to bypass the blower (it is installed in the end plate next to the blower drive).  This allowed the two sides of the blower to be more equalized hence taking nearly all the horsepower draw away from powering the blower, nearly allowing it to just free wheel.  Only problem with your setup is that I believe the bypass valve is set to open at around 10psi.  I am putting out about 15psi. Good Luck, TomC