1984 300SD Project

[jheppner]

Hi, my grandfather gifted me an '84 300SD with 262,000 miles. He was the original owner, and it's in really good shape.

I’m looking to get more horsepower out of it while keeping it reliable for daily driving. Just wanted to see if I’m on the right track with my plans. Any advice or recommendations? here is my current plan while doing as much research as possible, Mercedes are new to me.

Phase 1: Prep & Baseline (Make Sure the Engine is Healthy)
Install Bosch Monark Injector Nozzles
Check/replace fuel filters
Clean/replace fuel lines if needed
Cooling System Overhaul:
Install New Radiator (Behr/Nissens)
Replace Coolant Hoses
Upgrade to Electric Fan Kit (SPAL/Derale)
Flush & refill coolant
ATF Flush & Filter Change → Keep the 722.3 automatic transmission happy.
Install Boost & EGT Gauges → You need to monitor boost & exhaust gas temperatures before tuning.
Phase 2: Breathing & Exhaust Upgrades
Intake Upgrade:
Install Custom 2.5” Cold Air Intake
Delete EGR System (Use block-off plate)
Install 3” Turbo-Back Exhaust:
Removes backpressure → Frees up power
Get a muffler (if needed) to keep noise down
Phase 3: Turbo & Boost Control (More Power!)
Turbo Upgrade: Choose GT2259V (VGT) or Holset HX30W
If using GT2259V, install Powerstroke 6.0 actuator
If using HX30W, fab new turbo manifold adapter
nstall Manual Boost Controller (Start at 12-15 PSI)
Check ALDA (Fuel Enrichment) Settings
Adjust ALDA for slightly richer fueling
Phase 4: Fuel System Fine-Tuning

Fine-Tune Injection Pump (IP) Fuel Settings
Adjust full-load screw (Small increases only!)
Dyno tune or EGT gauge monitoring recommended
Adjust Vacuum Modulator / Shift Kit (For Firmer Shift

Phase 5: Final Reliability & Drivability Adjustments

Install Larger Oil Cooler (Optional but Recommended)
Fine-Tune Boost (Increase to 15-17 PSI if EGTs are safe)
Adjust Differential (Optional)
If better highway MPG is needed, swap to a 3.07 rear diff
Check for good shifts, low EGTs, & solid boost control
No excessive smoke, no overheating