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

Probably also replace the switchover valve. Located on drivers side firewall or wheelwell. Will severely impact power if clogged.

Sounds like a serious project for a great car. Good luck and let us know how it goes.

How about some pics.

Check the timing chain stretch before trying to get more power and either replace it or correct the valve timing with an offset cam gear woodruff key. Adjust the valve clearance, run it hard for about 1k miles and recheck the clearance. It can take 2-3 adjustments to get the clearance maintained if they haven't been done lately.
Sounds like the car landed in good hands! Keep us posted.

__________________
"Rudeness is a weak man's imitation of strength" - Eric Hoffer

Consider deleting the vacuum pump and going electric if it presents any hint of a problem, when they fail they can cause major problems.

__________________
"Rudeness is a weak man's imitation of strength" - Eric Hoffer

See if greazzer can set you up with dialed in nozzles.

__________________
"Rudeness is a weak man's imitation of strength" - Eric Hoffer

Check the intake manifold for gunk, pull it and clean it well. They can really get choked down but it is easy to check with a borescope.

__________________
"Rudeness is a weak man's imitation of strength" - Eric Hoffer

Thanks Sugar Bear, super helpful I'll start with that, picking the car up in April.
Tyl604 ill post pic when I get it.... super clean garage parked, he had sheep skin on the seats since day one, and no cracks on the dash.
I was thinking of posting it on bring a trailer but figured when else was I going to get such a clean reliable car.