My buddies 91 300D 2.5 Turbo has gone the way of the dinosaur... she broke her oil pump chain and seized .
So now she needs a rebuild (if we don't decide to go w/ a new engine for the warranty). And I (at least) am of the mind that if we have to rebuild it anyway, why don't we make it better than it was?
What I want to know is what is available out there for performance diesel parts and what would I need? I would want to find better pistons, tougher valves, race cam/crank, tougher head gasket, intercooler etc.... so that I could kick the boost up over twenty after I tear the freakin boost control out (obvioulsy I will put in another boost control system). Where can I get performance diesel parts?
My first thought was to bore it out, but I think that beefing up her guts and cranking the boost might give me better power for less $$.
Or should I beef it up and bore it out to, like, 3.0l??
I just can't see the point in all the effort involved in beating out the old pistons, redoing the valves, honing the cylinders, etc w/o kicking it up a notch!
I want to hear opinions and parts sources....leave one or both!!!
-Matt-

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Currently:
1972 350SL Euro 4spd
1973 BMW R75/5
1981 BMW R80GS
1995 FZJ80 with OM606 Conversion In Progress

Ya ! Now that it is broke, lets beef it up!

Bull---- I'd love to be in a position to un-beef your idea of bastardizing what may be salvageable MB!

It's not a small block Chevy, if you do a rebuild I would use MB factory parts and a machine shop that dose MB work.other than an inter cooler on a turbo model how could you improve on the factory design?

William Rogers.........

Lower the compression ratio. If you get the compression ratio down to 17:1 (I think the best way is to get slightly shorter pistons) and replace the cylinder head bolts with studs and nuts, you can safely get the turbo boost up quite a ways (possibly past 30 psi). With that, you can increase the fuel output.

Installing water injection will help lower the EGT's, allowing you to add still more fuel without damaging anything (if done right). Propane injection is also a possibility.

If you try any of these things, the first thing to do is install an EGT and a turbo boost gauge! Then follow them religiously...if you mount the EGT thermocouple before the turbo, make sure the temp never gets above 1200°.

There's more to it, but those are some of the basics...

The Warden,
Why would you replace the head bolts with studs and nuts??
I would believe that bolts, having one thread, would be more reliable and able to withstand pressure better than studs and nuts (with 2 sets of threads).
If it is due to factory bolts having a predertermined "stretch" and studs not, then just buy bolts which do not have the "stretch".
Please explain your logic.

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Tony from West Oz.
Fatmobile 3 84 300D 295kkm Silver grey/Blue int. 2 tank WVO - Recipient of TurboDesel engine.
Josephine '82 300D 390kkm White/Palamino int.
Elizabeth '81 280E, sporting a '79 300D engine.
Lucille '87 W124 300D non-turbo 6 cylinder OM603, Pearl Grey with light grey interior


Various parts cars including 280E, 230C & 300D in various states of disassembly.

Sorry to hear the pump chain broke - this is the first time I've heard of that failure.

I think the aftermarket performace market for this car is very limited - most everybody that buys a 300D is looking for great fuel economy and low operating costs. No demand = no supply.

Like a previous poster said - this is not a small block Chevy - you are going to find some of the prices for parts on this engine absolutely breathtaking.

For example the stock pistons are something like $400 per copy, fuel injection mods can get pretty pricey as well.

Your stock engine has 120hp, after all your mods you might get it up to what? 160, 170 maybe 190HP?

Why bother? A V6 Camry will still be able to walk away from you...

Thanks for the input, guys. First off I am a very serious Mercedes guy. Normally I hate mods, even improper rims for the year get on my nerves sometimes (I especially hate re-badging a car to make it look like you have a higher model; 300E re-badged to a 500E etc). This car is very fast already and this w124 chassis can handle lots of speed. I love the drive and I love the diesel (I've owned 4 MB diesels so far, love them all). Before she dropped the oil pump chain and went to the great beyond, the spring in the waste gate started to sag a little, so she was only putting out about 9psi of boost, but was still the fastest (MB) diesel that I've ever been in. I know the turbo in that car is capable of well over 25psi and just thought that while it was apart I might beef it up and get a little more boost out of it. Most of the components on the engine and drivetrain (being MB) can handle a ton more than they get and I was just wondering where the 'weakest-link' would be in, in terms of adding power.

-Matt-

The only mods that I am enthusiastic about are 'proper' lights and the correct 5-spd stick that my car should have!

__________________
Currently:
1972 350SL Euro 4spd
1973 BMW R75/5
1981 BMW R80GS
1995 FZJ80 with OM606 Conversion In Progress

Are there bolts out there that do not have the "stretch" and are capable of torquing to the same specs and holding the same pressure that the factory bolts can handle?

Maybe the M-B engines are different, but most American-built diesels use torque-to-yield bolts that are only good one time. The stud setup doesn't have that limitation, and as a result allows a person to safely put more torque on the nut, allowing for more clamping force on the head gasket. Most of the truck diesel guys who are increasing their boost pressure go to this setup for this reason. Heck, some people with the 6.9l IH diesel (like what's in my truck) replace their bolts with studs just to keep the head gaskets from blowing. I would be doing this myself, but with a V-8 engine a stud installation requires that the engine be removed from the vehicle, and I'm not prepared for that...

Keep in mind you have an aluminium head. It's not like an Iron Cummins head where they use a torque (450ft. lbs?)+90* turn method to tighten the bolts.

It's VERY easy to warp an alu. head by over torquing, ask me how I know...

Well, I personally don't have one. But I see your point...I didn't think about that.

However, if you knew somebody with the time and BIG $$$, one could make an iron casting based on the aluminium head. Then you could safely make some REAL power!

Best of both worlds! Now that would be ...

wdba123190 I love your ideas, a fast MB diesel would be cool. But before going and droping $20k on the engine, a nice 500E can be had for the mid $20's. A stock 500E will still destroy a modified diesel W124. 300D for Monday-Friday. 500E for Sat-Sun.

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1999 SL500
1969 280SE
2023 Ram 1500
2007 Tiara 3200

The stretch bolts are required to keep the head gasket intact -- the aluminum "grows" considerably more than the steel bolts, so if the head bolts don't stretch and remain elastic, the head gasket will get overcrushed and then leak when cold.

The only modifications you are going to be able to do without getting new pistons custom made for you (they are die cast, by the way, not machined, so you can figure the cost for custom ones!!!) are to install an intercooler and raise the boost. Propane injection and low compression/high boost are out of the question for this engine, they will require modifications you won't want to pay for (and I have questions on the safety of propane injection on prechamber diesels anyway).

The reason you can screw so much hp so easily from US made pickup truck engines is that they are seriously de-tuned to reduce the hp output to save the featherweight drivelines -- the 5.9L Cummins is rated for at least twice the hp in medium truck applications. This is not true for the MB diesels in cars -- they are designed to a different philosophy, and sacrifice raw hp for much higher rev limits, much better milage and less maintenance. My 300TE get 19 mpg in town, 22 on the highway, the 300D gets 30 in town and 32 on the highway with the same performance.

I'd stick with a plain jane rebuild since you are looking at nearly $5000 in parts anyway (plus 50 hrs book time) unless you can save the pistons. If you want a screamer, buy a gas engine, it's cheaper, easier, and much more effective

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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!

VW diesel guys (alum head) have been replacing the stretch head bolts with stud kits for ages to reduce head gasket problems on tweaked turbo diesels. It's a well proven tactic.
Maybe there's some technical reason it does not work with MB, who knows. But it works like a charm on VW's. You'll never replace a head gasket when using studs on a stock boost engine if you don't overheat and warp something.

Course I've never replaced a headgasket on one period, over a million miles in them between father and I.. ~shrug~

The Warden covered the rest of the common place diesel mods. People don't think diesel and performance, but the full size domestic truck crowd and especially the tractor trailer builders have been upping HP and keeping reliability and longevity for a very, very, very long time. It's not a black art, just expensive and uncommon to normal techs/hobbyists.

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One more Radar Lover gone...
1982 VW Caddy diesel 406K 1.9L AAZ
1994 E320 195K