Recommended Pre-Turbo Install Prep?

[Duncan Sterling]

Greetings All,

I've got a '91 R2500 fleet spec (ex NYC firetruck) Suburban with an NA J motor and a first year 4L80E. 3.73 rear axle, and the motor's got about 126K on the clock.

If you go by the factory VIN decoder, this truck is supposed to be able to tow #9000 as is (so figure realistically about #6000).

It's towed my old #2000 boat OK, but I just picked up a #6000 boat, and now I'm strongly suspecting that it's not going to do so well with towing the bigger rig.

So, I'm thinking seriously about picking up a Banks turbo (already installed the stinger intake/exhaust kit 2 years ago, though I didn't mess with the pump).

Now before I pick up the turbo, I'm thinking that I probably ought to do some prep work. The list of items/questions I have in mind is:

1) Replace the current injector pump--I have a DB-4911 core, so I'm thinking it'd make sense to replace the old pump (4275?) with the 4911, which was factory calibrated for the turbo (right?). Need to save this until right before I put in the turbo though, because it'll run high EGTs otherwise (even with the stinger exhaust system), right?

2) Replace the old worn injectors--but not with stock, maybe Kennedy hi pops? Or Peninsular marine injectors?

3) Replace the old glow plugs--with 11Gs? Or with Kennedy quick heats?

4) The truck has a factory trans cooler in front of the radiator, but I wonder if I should replace it with a larger one? With a dedicated electric fan?

5) No engine oil cooler, except in the radiator (factory stock), should I add an external oil cooler in front of the radiator? Also with it's own fan?

6) Maybe a higher performance Kennedy fan to replace the stock one?

7) Compression test before I sink big bucks into all the above parts. Oil pressure seems OK, and I'm not seeing oil smoke (or using much, maybe a quart every 3K miles), but what minimum compression should I be looking for before I start looking for a new motor/short block instead?

The final question is of course, what might I be missing here?

I've already done the harmonic balancer and the rubber core main pulley, and changed out the radiator with a fresh one.

TIA for any and all input/suggestions/advice/ideas/pointers, etc.!

--Duncan

[More Power]

1) Replace the current injector pump--I have a DB-4911 core, so I'm thinking it'd make sense to replace the old pump (4275?) with the 4911, which was factory calibrated for the turbo (right?). Need to save this until right before I put in the turbo though, because it'll run high EGTs otherwise (even with the stinger exhaust system), right?

2) Replace the old worn injectors--but not with stock, maybe Kennedy hi pops? Or Peninsular marine injectors?

3) Replace the old glow plugs--with 11Gs? Or with Kennedy quick heats?

4) The truck has a factory trans cooler in front of the radiator, but I wonder if I should replace it with a larger one? With a dedicated electric fan?

5) No engine oil cooler, except in the radiator (factory stock), should I add an external oil cooler in front of the radiator? Also with it's own fan?

6) Maybe a higher performance Kennedy fan to replace the stock one?

7) Compression test before I sink big bucks into all the above parts. Oil pressure seems OK, and I'm not seeing oil smoke (or using much, maybe a quart every 3K miles), but what minimum compression should I be looking for before I start looking for a new motor/short block instead?

The final question is of course, what might I be missing here?


1- Ask that they rebuild your 4911 to 1992-93 6.5TD specs. You could install it anytime. Your right foot is what will limit fueling. If it's smoking, back out of it.

2- I recommend using injectors that match the injection pump's fuel-rate calibration (i.e. If you're installing DB2-4911 with a factory fuel-rate calibration, then factory 6.5TD injectors would be a good choice). Ask any vendor who is offering "marine", "hi-pop", or "hi-flow" injectors whether they have an engine/vehicle dyno analysis that makes the case for their "performance" injectors. I'd bet some of those selling "performance" injectors don't even know the pop pressures and flow rates. Stick with those that do... :)

3- Use the AC-60G glow plugs or an aftermarket equivalent that offers PTC (Positive Temperature Coefficient) operation.

4- Install a trans temp gauge. Knowing what sort of trans temps your rig is generating will help you decide what if anything needs to be done with ATF coolers.

5- It's a toss-up... The in-rad engine oil cooler is pretty efficient, but it also adds heat to the cooling system. If you're not having excessive engine temp issues, I'd leave it. If you're having high temp issues, then an external engine oil cooler would be a good idea.

6- High performance fans and fan-clutches are available for the serpentine belt systems. I'm not aware of a proven hi-performance fan and fan-clutch system for the v-belt drives.

7- Most healthy 6.2/6.5 engines develop 350-400 psi cranking pressure. GM says that 275 psi is the minimum, with no more than a 10% difference between the highest & lowest reading cyl.

This'll get you going!

Good luck,

Jim