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  #1  
Old 05-21-2011, 09:46 AM
David Sims's Avatar
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91 350 SD Head/ MPG questions

I have been looking for a late 126 diesel or a W140 diesel. I have a good 1982 SD daily driver with cold ac (thanks Jim Ellington). The spare car is a 240 Euro. One of the cars I plan to look at soon is a 1991 350SD, 240K total miles and a factory rod update at about 80K for $7,700. A Craig's link should show here. http://atlanta.craigslist.org/search/cto?query=mercedes+diesel&srchType=T&minAsk=6000&maxAsk=8000

Here is what my research shows on the head issue. Please correct or add as needed:

1) The most desirable head has the #22 casting. The 7th and 8th digits in the casting are the "important numbers".

2) The location of the casting numbers are around the #2 and #3 injectors.

3) Heads that are bad or at least not desirable would be 15, or 17, or 20.

4) The #22 head was not standard issue on any W126.

Fuel mileage:
I drive 50 miles most days and usually drive under 65. My SD gets 26 to 28 most tanks. The 240 Euro with new injectors (I'm pleased with the Sean Watts injectors) I get high 20's and low 30's.

I'm wondering what I will give up on mpg with a 603 engine in a W126 or W140. A general answer from your own experience/research is what I'm looking for. All things being equal, which will return the best mpg an older SD with the 617 or the 603 in a W126 or W140?

All comments welcome.

Thanks,

David

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  #2  
Old 05-21-2011, 09:49 AM
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I'm going to bet the 350SD gets better. not sure about the 140... I would guess better still, but I do not know.
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John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 190D 2.5Turbo
1987 190D 2.5-5SPEED!!!

1987 300TD
1987 300TD
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  #3  
Old 05-21-2011, 09:52 AM
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Quote:
Originally Posted by vstech View Post
I'm going to bet the 350SD gets better. not sure about the 140... I would guess better still, but I do not know.
X2
A 60x is going to be better fuel wise than a 61x.
20 years of development must have done some good even allowing for the bad rods.
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1967 230-6 auto parts car. rust bucket.
1980 300D now parts car 800k miles
1984 300D 500k miles
1987 250td 160k miles English import
2001 jeep turbo diesel 130k miles
1998 jeep tdi ~ followed me home. Needs a turbo.
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  #4  
Old 05-21-2011, 10:19 AM
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The head issue is for the 300sd. My understanding is the 350s all have the good head. They traded the good head for weak rods.
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  #5  
Old 05-21-2011, 10:46 AM
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The 140 is a lot bigger and heavier than the 126 I would be surprised if it does not use more fuel than the 603 engined 126.
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..I also have a 427 Cobra replica with an aluminum chassis.
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  #6  
Old 05-21-2011, 10:48 AM
t walgamuth's Avatar
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my 91 350sdl used more than my 617 equipped 126 iirc. It was smoother quieter and more powerful though.
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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.
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  #7  
Old 05-21-2011, 11:06 AM
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I get 19/26 in mine.

-J
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1991 350SDL. 230,000 miles (new motor @ 150,000). Blown head gasket

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  #8  
Old 05-21-2011, 12:20 PM
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everything being equal, the 350 should be better on fuel than the 3.0. of course, it has more power, and is capable of putting it to the pavement faster, so your foot can cause a decline in economy. if driven under 65 and rabbit starts are avoided, the 350 should do better on fuel.
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John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 190D 2.5Turbo
1987 190D 2.5-5SPEED!!!

1987 300TD
1987 300TD
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!
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  #9  
Old 05-21-2011, 01:47 PM
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Quote:
Originally Posted by David Sims View Post
3) Heads that are bad or at least not desirable would be 15, or 17, or 20.
#17, #18 and #20 heads are more desirable than the original #14 head on 3 liter blocks. Make sure a #14 head is bad before you remove it because many live long and happy lives, though it's reasonable to fit a later head when a #14 head comes off for other reasons. I don't think anyone would replace a #17, #18 or #20 head with a #22 head for good measure. Of the series, the #14 head has a higher likelihood of developing cracks when overheated. The rest have pretty much the same likelihood. IIRC, other casting numbers in the series represent normally aspirated and non-US applications.

Assuming my right foot didn't gain or lose weight over the years, my 81 and 83 SDs didn't get the fuel mileage of the 87 SDL and 93 SD 3.0, which didn't get the fuel mileage of the 87 300D. I didn't have enough time with the 93 SD with it's original 3.5 to measure fuel mileage.

What are your priorities and requirements other than fuel mileage? A 93 SD provides such a different driving experience than an 83 SD and the cost to procure and maintain are also so different that the difference in fuel mileage is just a sidebar in the consideration.

Sixto
87 300D
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  #10  
Old 05-21-2011, 01:52 PM
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smoke gets in your eyes
 
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You might look into a 90-93 300D 2.5. You have to struggle to get less than 30mpg in one of those.

Sixto
87 300D
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  #11  
Old 05-21-2011, 03:15 PM
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priorities and requirements

Sixto,

Thanks for the head info. To answer your question safe, reliable, efficient, clean.

Most if not all of the MB line would satisfy the first requirement. I do like the S class. W140 first (never owned one) then the W126.

The 61X have all been reliable for me since my first one, an 85 300D bought in 1990. Anything over 25mpg is ok for now but that requirement keeps moving upward. I keep parts cars, 2 W123 and 2 W126. I'm no mechanic but can change parts and keep all the fluids clean.

Last but not least it must look good, drive out perfect, non smoker, garaged.

I'll take a look at the 90-93 300D 2.5.

Thanks,

David
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  #12  
Old 05-21-2011, 07:35 PM
compress ignite's Avatar
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KBB

1991 350SDL

Current Owner (3rd, in Atlanta) ,Failed Mathematics (In high school?) [Price]

Retrofitting to R134 in the South should knock the $1,500 to 2,000 necessary
to Re-Retrofit it from the KBB price.
(Which puts the Real World Price @ $2,800.00)

This Chassis Does Not Have a Mercedes Remanufactured Engine !

I'd have to see the receipts from the Mercedes Parts Depot (Baltimore?) for
the updated rods to RBM.
AND I'd wanna talk to the Tech who performed the Surgery.
('Seen some Excellent work [And some real Hack Jobs] roll out the shop door
onto Roswell Rd.)

'looks like this is a $1,500.00 (Total Sales Price)Experiment in Future Automotive Expenditure.
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91 350 SD Head/ MPG questions-screenhunter_02-may.-21-19.30.jpg   91 350 SD Head/ MPG questions-screenhunter_03-may.-21-19.35.jpg  
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Last edited by compress ignite; 05-21-2011 at 07:53 PM.
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  #13  
Old 05-21-2011, 09:46 PM
David Sims's Avatar
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KBB

Compress Ignite, I appreciate the KBB info and advice. David
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  #14  
Old 05-23-2011, 08:45 PM
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Call this guy in Columbus, Ohio with the 120,000mile '87 300SDL, he's the original owner, see what he'll take and you can drive it for another decade or more.
87 300D & '87 300SDL for sale by original owner
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  #15  
Old 05-24-2011, 08:45 PM
David Sims's Avatar
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Southern car

babymog, I think I'll stick with a Southern car but thanks for the tip.

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