I'd like to locate a specialist who prepares 603 motors for more power. Just a good old overbore is what I mainly would like. The power curve and driveability are perfect, I just want more. I can speak some German, so a shop in Germany would be fine.

No, I don't want to go to the turbo because they are rare here in France where I'm living for a while. I don't need head cooling problems either.

Regarding those head cooling problems, has anyone tried just changing the gearing on the water pump drive, so it turns 10% faster? A slightly smaller pully on the water pump should help.

__________________
Thx/Reno
An American in France
88 300TD 5spd Sportline (lowered factory susp) - totalled by a flying deer
89 Range Rover V8 - the 4wd beast
02 Toyota minivan
05 Peugeot Partner 4x4 Dangel
88 International Harvestor 633SA
--Gone but not forgotten:
1970 250/8 C (sold to buy 450 SLC)
1972 450 SLC (sold after battling wiring harness problems too long)
1971 300 SEL 6.3 (sold after destroying two *very* expensive rear LS diffs)
1986 560 SEL (now my little brother's pride and joy)

If you let the car overheat you will have head cooling problems. My stock cooling system does just fine on 90+ degree days in traffic. How are the natural 603's on power? I really like the turbo on mine it really starts to move over 3k rpm.

__________________
1999 SL500
1969 280SE
2023 Ram 1500
2007 Tiara 3200

Reno,

Why would you want to change something that you call perfect?

It is unlikely that running the water pump faster will make the engine run any cooler as it will not increase heat transfer to the cooling air. What will help is replacing the radiator with a radiator with a higher BTU transfer capacity.

P E H

Regarding cooling, what you say above is exactly correct. But over here in Yurrup a major magazine recently printed a reliability study of MBZ diesels, and it noted that the cylinder head in turbo 3.0 diesels suffers hot spots that cause damage to the head gasket and head. Cars are generally run faster and harder here than in the US (the speed limit here in France is 83mph, and you can cruise all day at 95 without getting nailed). My reasoning is that flowing more coolant thru the head would reduce hot spots when running hard. OTOH, a specialist in pumping up Benz diesels would probably already know a cure for the issue.

BTW, the atmo 603s came out on top of the reliability comparo. The article said that Benz has not sold a diesel quite so reliable since the 603. All the newer CDI models have more problems, with some of them pretty dismal.

__________________
Thx/Reno
An American in France
88 300TD 5spd Sportline (lowered factory susp) - totalled by a flying deer
89 Range Rover V8 - the 4wd beast
02 Toyota minivan
05 Peugeot Partner 4x4 Dangel
88 International Harvestor 633SA
--Gone but not forgotten:
1970 250/8 C (sold to buy 450 SLC)
1972 450 SLC (sold after battling wiring harness problems too long)
1971 300 SEL 6.3 (sold after destroying two *very* expensive rear LS diffs)
1986 560 SEL (now my little brother's pride and joy)

I guess when I say "perfect" I really should say more

It feels like a gas motor in that the power builds steadily with RPM, until about 4500. The manual says it can go a bit higher but I shift at 4500 in consideration of my high mileage (360000 kilometers = about 220k miles.

Off idle, the torque exceeds significantly that of a gas motor. You have to really be a bozo on the clutch to stall it That's right, I said clutch. W124 OM 603 912 atmos came with a standard 5spd manual transmission, and automatic trans were a rare option. OTOH, the OM 603 960 turbos came only with the 4spd automatic. The automatic sucks down enough power to make the 300 turbo only 2mph faster in top speed than the 250 turbo, which has only 126HP but a standard 5spd manual trans.

With the 300 atmo, power starts to pick up at about 2500 RPM, she starts to sing at about 3000, and the exhaust gets that charactaristic "ripping sheets" sound of an inline 6 with optimized valve timing at about 4100.

That said, peak HP is only about 110 so you guys with turbos would have me firmly in your rear view mirrors easily. The atmos are no slouches for diesels, but turbos and modern DI turbos are clearly faster. However, it's not uncommon for an atmo 603 to go 600000 kilometers (400k miles) with no major service except perhaps a head gasket.

__________________
Thx/Reno
An American in France
88 300TD 5spd Sportline (lowered factory susp) - totalled by a flying deer
89 Range Rover V8 - the 4wd beast
02 Toyota minivan
05 Peugeot Partner 4x4 Dangel
88 International Harvestor 633SA
--Gone but not forgotten:
1970 250/8 C (sold to buy 450 SLC)
1972 450 SLC (sold after battling wiring harness problems too long)
1971 300 SEL 6.3 (sold after destroying two *very* expensive rear LS diffs)
1986 560 SEL (now my little brother's pride and joy)

5spd awsome! Turbo 603's seem to hold up real well to, their are many example's running around with 400k+ miles on them. Mine has 235k and runs perfect, no blow-by at all. What is red line on it? Mines good for just under 5k. I also get about 24mpg-25mpg around town.

__________________
1999 SL500
1969 280SE
2023 Ram 1500
2007 Tiara 3200

5spd awsome! Turbo 603's seem to hold up real well to, their are many example's running around with 400k+ miles on them. Mine has 235k and runs perfect, no blow-by at all. What is red line on it? Mines good to just under 5k. I also get about 24mpg-25mpg around town.

__________________
1999 SL500
1969 280SE
2023 Ram 1500
2007 Tiara 3200

Hi Reno.

This is the place to go:

http://renntechmercedes.com/

Louis.

Um, I highly doubt that Renntech offers any upgrades for diesels.

Mercedes put a different water pump pulley and belt on the 3.5L engines to spin them faster. It wasn't to increase cooling, it was because the 3.5L engine had a significantly lower max RPM (4400, I think) and spent most of it's time at 10% lower speeds! I wouldn't mess with that. The stock cooling system should be more than adequate if maintained properly. Install a 603 Turbo radiator if that's larger/different but leave the rest alone.

The head "hot spot" issue is a load of crap, IMO. The original turbo heads were all flawed. MB redesigned them FIVE TIMES (that's six different heads). The later ones have almost no cracking problems. I'd forget trying to pump up a non-turbo 603, and swap in a 603.96x and be done with it. That'll give you 148hp stock, and with the Mosselman intercooler kit, you can bump that to ~175hp.

__________________
Dave
Boise, ID
Check out my website photos, documents, and movies!

I had to dig to find the 124 section there!

No diesel info ...

__________________
Thx/Reno
An American in France
88 300TD 5spd Sportline (lowered factory susp) - totalled by a flying deer
89 Range Rover V8 - the 4wd beast
02 Toyota minivan
05 Peugeot Partner 4x4 Dangel
88 International Harvestor 633SA
--Gone but not forgotten:
1970 250/8 C (sold to buy 450 SLC)
1972 450 SLC (sold after battling wiring harness problems too long)
1971 300 SEL 6.3 (sold after destroying two *very* expensive rear LS diffs)
1986 560 SEL (now my little brother's pride and joy)

Husker:

The 603 is a sleeved engine, so an overbore probably isn't much of an option.

A used 603.96x would be cheaper, most likely -- piston set is about $2500 for the turbo, probably cheaper for the atmo, but not cheap.

Peter

__________________
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!

Oh man, I feel like a K-Mart shopper. I always thought I had an iron block. I thought that sleeved iron blocks went out with Ramblers, eh? Maybe it's just that I have so much gunk on my block that I can't tell what metal it is.

So if it's indeed sleeved, you're right in that there's very little room for boring it out more. Are they wet sleeves?

__________________
Thx/Reno
An American in France
88 300TD 5spd Sportline (lowered factory susp) - totalled by a flying deer
89 Range Rover V8 - the 4wd beast
02 Toyota minivan
05 Peugeot Partner 4x4 Dangel
88 International Harvestor 633SA
--Gone but not forgotten:
1970 250/8 C (sold to buy 450 SLC)
1972 450 SLC (sold after battling wiring harness problems too long)
1971 300 SEL 6.3 (sold after destroying two *very* expensive rear LS diffs)
1986 560 SEL (now my little brother's pride and joy)

That is damn good news. I'd really love to have a 300TD turbo in the garage too, but that head damage issue scared me off.

Do you have part numbers for the new heads? Or any source for further documentation on the web or elsewhere? I can read German if needed. When I speak it, Germans make faces and cover their ears, but by God I can read it.

__________________
Thx/Reno
An American in France
88 300TD 5spd Sportline (lowered factory susp) - totalled by a flying deer
89 Range Rover V8 - the 4wd beast
02 Toyota minivan
05 Peugeot Partner 4x4 Dangel
88 International Harvestor 633SA
--Gone but not forgotten:
1970 250/8 C (sold to buy 450 SLC)
1972 450 SLC (sold after battling wiring harness problems too long)
1971 300 SEL 6.3 (sold after destroying two *very* expensive rear LS diffs)
1986 560 SEL (now my little brother's pride and joy)

What is an atmo? Is that what we call a NA?

P E H