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1985 300GD LWB 5 Speed
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Discussion Starter #1
I was suffering the ping ping of a poorly functioning fuel injector. I removed all of the injectors and took them to a shop for testing. One turned out to have a poor spray pattern and release point. While at the shop I noticed some prechambers on the counter - an old one and a new one for another customer's 300 diesel. The parts looked different as I looked through the port at the top. The parts man said that these had been upgraded some years ago, and that I could use them in my G. So, I bought five and installed the upgraded prechambers.

Tonight I finished the reassembly, and after a few minutes of run in shaking and snorting, the engine smoothed back to its normal operation. I took the car for a drive, and I must say, it runs better ever. The power curve and overall operation is much improved.

I do not know why the prechambers were reeniginered by MB, but if that is part of why I have improved operation of my old 300...I like it.
 

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1980 LWB 280GE
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I hope they weren't from a 617.95x

The "introduction to service" manual for the turbodiesel made it pretty clear that the prechambers were not interchangeable with those of normally aspirated motors.

-Dave G.
 

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1985 300GD LWB 5 Speed
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1,079 Posts
Discussion Starter #3
No, the only changes in the new ones is an internal modification, that is, slightly larger hole where the injector rests against the prechamber. Other wise they are the same injector, just "modified". Naturally, there is a heat shield that goes in around the edge of the hole, which protects the bottom of the injector.

I think the flow from the injector into the prechamber is slightly improved, making the engine operate smoother in all ranges of power. The part numbers match exactly to my old prechambers.

How goes the engine transplant, Dave? A friend here is switching his 300 non-turbo to a 300 turbo. He is following your progress with great interest.

Once done, you will need to point that red machine to the Pacific Northwest for a visit.
 

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1980 LWB 280GE
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Going well. I even managed to expand the job a little and find a trans from a delivery van that will get me a slightly lower first gear, as well as an over-drive that will allow me to cruise at 80 at 3200 rpm.

It's a G1/18-5/4.7 box like the one they put in the 290GDT461s (though not the same 711.117 part number due to the van appliation - output flange needs swapped). It's tailored nicely to the power curve of the turbodiesel, when used with 4.9 diff gears.

One minor glitch last night. Discovered the oil pump drive chain has begun shedding the center plates from it's double roller chain. Have to get it off there and check the sprockets. I figure I'll probably at least replace both chains (OP and Timing). Maybe the guy I got the engine from will feel bad enough to give me the parts. [;)]

But yep, things are progressing nicely. Anyone who has a 300 GD to start with would find this swap a nice weekend diversion. I'm having to work my way through a bunch of little nagging things converting the gas truck. It's all going well though, and just about to plan.

I dropped my intake and exhaust manifolds off for ceramic coating last night to help manage heat issues and keep the intake cooler. I was working on swapping the oil pan over to the beefier unit from the 951 motor when I discovered the chain. Not too much left still on the list. I gotta port the head a little, and rebuild the turbo. But I think that's about it. Couple hours work, then it's just doing assembly work as parts arrive from various places.

-Dave
 

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Discussion Starter #5
Dave,

I had a discussion with the local friend about porting the head excessively. I have heard his argument before, namely, that it is ok to port the opening to match the manifold, however the rough surface left by the sand casting of the head (and perhaps the manifold too) offers special and helpful, if not unplanned, air flow turbulance, which acts to enhance diesel operation. Have you actually run into that notion yourself or is this an urban mith?
 

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Thomas.Schumacher - 3/24/2005 11:32 AM
...the rough surface left by the sand casting of the head ...offers special and helpful.... air flow turbulance, which acts to enhance diesel operation. Have you actually run into that notion yourself or is this an urban mith?
I've never heard of it. That's not to say it isn't true. But I don't think it's an issue either way in my case since my crude porting job probably isn't any smoother than the casting.[:)]

I'm only taking the turbo, head, and manifolds out to match the gasket openings. I've heard direct first hand experience that doing this improved performance, some times remarkably, so I'm going for it.

-Dave
 

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'92 E300 TD '96 Peugeot 106D 12 Motorbikes
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Hi,

Thread's dead, but I'd like to comment anyway.

I think the diesel engine would respond to improvements in gasflow in a similar manner as a petrol engine.

Face and joint matching, coupled with smoothing and even polishing of ports, particularly the inlets (although the exhausts are also significant) will improve breathing and hence the capacity to produce more power. Or use less fuel.

Substitution, modification or meybe only adjustment of the fuel pump will complete the exercise, which if thoughtfully done should be worthwhile both in terms of performance and economy.

I have never tuned a Diesel, although I dabbled a little with both two and four stroke petrol engimes.

All the Best,

A.
 
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