Ok lets stirrrrr it up, I have a 83 SDL with the 5 cyl. and a 86 SDL with the 6 cyl. one will have to go . Which will be the better (in the long run vehicle)? Any tech. data on which is the better engine? Thanks Jerry

Keep the 1983 300SD, it will be cheaper in the long run. Just wait until you blow a head gasket, or crack the head even, then you will wish that you have sold the 1986 300SDL. If you are after the speed and don't care about the repair bills, then keep the 300SDL, and sell the 300SD.

Depends 123c, how much do you enjoy adjusting those valves on the 5cyl?

Keep the '83 SDL. Its not a question, its a fact.

Nothing quite like an 86 or 87 300SDL.. ditch the smokey old 5 cylinder. The ride and refinement of a 2nd generation w126 is miles above your old 83 300SD.

You aren't going to crack your head if you keep the car within normal operating temperatures.. my car has the original engine (including head) and transmission at 312,000 miles. Only major things that were done to the drivetrain was a front transmission seal at 210,000 and a timing chain and tensioner replacement at 270,000 as preventitive maintienence.

I am going to have to agree wih you on that point. I always hear the nitemare stories about the aluminum heads on gas engines, but I have never had a cracked or warped head, or a blown head gasket, mostly because I dont drive them hot. A little attention to the guages saves lots of headache and dollars in the long run. Bu overall I would like to know some stats on both engines as in average lifespan of each engine (in miles) and any abnormally weak areas and stregnths of each.

jerrymac-
You do not mention the condition of either car, or the mileage?

I would sell the BOTH and pick up a 560SEL - now THAT is a bulletproof engine

Mike

In a time like this, a 560SEL probably isn't the most economical decision...

Speedy -
I responded to your post, but started a new thread so as to avoid possibly "highjacking" Jerrymac's thread. Its called V8 Vs. diesel.

Mike

How do you say a The 5.6L M117 engine is "bulletproof"? Timing chain, tensioner and guides every 100K? Valve guides and seals every 150K? Worn camshaft lobes? And ofcourse, spark plugs, wires, distributor cap and rotor? Not to mention that electro-mechanical Bosch KE (?) Fuel Injection system.. Yes the bottom end might be great but everything else around it needs to be replaced.

I do love the simplicity of the old 617 motors, but the smoothness and power of the 603 is just awesome in comparison. Yes, there is more "stuff" in the engine compartment, but everything has its ups and downs

I will admit that I've never driven or ridden in a 603-powered car, but I for one prefer the brute indestructibility of the 617. It's true that you won't kill a 603 unless you overheat it, but that's just not a chance I'm all that willing to take. Besides, the 617 that I've got does everything that I've asked of her, and still is much more comfortable than the 6.9l Cornbinder in my truck

So, my vote goes for the 617 if all else is equal, but as others have pointed out, which one's in better shape overall?

__________________
2001 VW Jetta TDI, 5 speed, daily driver
1991 Ford F-350, work in progress
1984 Ford F-250 4x4, 6.9l turbo diesel, 5 speed manual
Previous oilburners: 1980 IH Scout, 1984 E-350, 1985 M-B 300D, 1979 M-B 300SD, 1983 M-B 300D
Spark-free since 1999

I'm with turbodiesel on the potential expense of the 560sel.
I'd like to add a price list. Fuel distributer: $700+, Jetronic
control unit: $1,400, catalytic converter: $900+, and another
dozen components most of which are over $100. Unless
you have a wholesale connection this is more expensive
than either diesel, and troubleshooting the gas model often
becomes a random replacement of parts, since the dealer
or shop has little interest in doing what it takes to find
the problem at a minimal cost. (based on my experience)
The diesel is more obvious when things go wrong.
I do not mind adjusting the valves every 15k on my
82' 300sd. It is a pain but not when considering that
hydraulic lifters can go bad and that requires removal of
the camshaft (and hence timing chain, and hence a
special tool) and I don't want to do that in the parking lot.
I have never driven a SDL, so my point is to keep one
of the non-catalysts and avoid the 560.

Turbo - By bulletproof, I mean I have never heard of an M117 with a cracked head. Nor do they have a trap oxidizer to deal with. The lower end will last almost indefinitly. Just as many things will have to be replaced on your engine and the Bosch EDS basically the equivelant of the Jetronic system.

Worn camshaft lobes? Change the oil and that is not a problem. Timing chain is a maintaince item. I notice you changed yours recently.
Distributor cap and rotor? Maintenace items that have nothing to do with the longevity of an engine. Gassers have spark plugs, you have glow plugs.

Someone mentioned the cats on the 560 being a problem...I would still rather have those than the trap O. and the diesel EGR valve.

The 603 engine is not what I would describe as bulletproof, as there are major, known problems. I do notice you have some serious miles on yours, so its easy to see why you would defend this powerplant.

Mike

You keep mentioning the trap oxidizer which is a free replacement item by Mercedes-Benz, and 99% of the cars have had the recall done already.. there is absolutely nothing to worry about.

Yes, I changed my timing chain and tensioner at 270,000.. With a 560SEL I would have had to change that plus the guides atleast two, maybe three times already. Glow plugs are good for years and years, I think mine lasted 240,000 miles. Not to mention all the sensors and lambda this and that on the 560.. no thank you. Yes you will change the oil regularly, but how about the previous owner.. I assume you didn't own this car since new. Is it a fast car? Yes. Is it "bulletproof"? By no means.