OM617.951 v. OM617.952 -- What's the Difference?
 

I happened to wonder about this, since my understanding is that the '84 300D that I have is a .952 versus the 300SD which is a .951. Wondering what the difference between the two was, I googled it and found the following result on Wikipedia:

...really? Is that the best-kept secret about the 300SD, or am I just living under a rock? What is the difference between these two?

Well I know that rear sls was an option in the s class, at least for some of it...

...but in the 300SD??? Sorry... time to go to bed, I guess...

The 617.951 is used in the W126 from 81 - 85. 123HP
The 617.952 is used in the W123 from 82 - 85. 123HP

The long block is the same between the two. the differences is the SD has an electric signal for the oil pressure, and the 300D has a oil line going to the gauge.

The engine mount arms (aluminum) are specific to each chassis IE different part #. they both use the same engine mounts. (rubber).

The Oil Filter Housing has a different angle to one of them and the plate on the back side for the oil pressure reading and where the Turbo Oil line connect is different. they won`t swap between the two housings.

The 300SD didn`t have a SLS system.

The W123 300TD has the SLS pump mounted on the front of the head, and the 617.952 is the same engine except for the head has the mount for the Pump. the head will swap over to the SD and 300D. just need a blocking off plate for the pump.

The 300TD with the 617NA engine and the 300D 617NA up to 81 is the same engine except of the SLS Pump on the TD. think this eng is 88HP.

The W116 from 78 - 80 uses the 617.950 engine, rated as 110HP as I remember, and no SLS Pump.

There are some very rare TD`s with the 240D engine.


I have seen the SLS on some of the second Generation 126 from 86 - 91. usually on the 560SEL and have seen it on a Euro 500SEL. some times the hydraulic`s are just on the rear, and have seen it on all 4 corners.


Charlie

Well done Charlie !! Thanks for the full clarification.

Whoa... that answers all my questions, and then some. Thanks, Charlie!

My 81 300TD turbo wagon has a .951. First year bastard child thing. Also has the 126 300SD transmission.

Are you saying that is a factory .951? I've seen quite a few '81's and they all had the .952 and a 303 trans.




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Engine swap clarification
 

Thanks for this great write-up Charlie. I'm still not entirely clear on whether I can install a 952 in a 300SD. Is this possible with the swapping of the engine mount arms and oil filter housing? Or are you saying that a swap is not a straight forward install with the swapping of some parts?

Thanks.

Tom

Yup, just swap the mount arms, oil filter housing (I think you'll need to buy a gasket for that), and some AC lines (presumably the ones running to the evaporator).

Yes a 952 will install into a 300SD. The engines are the same, just change the Aluminum engine mount arms, the Oil Filter Housing, and I believe the Oil Cooler lines are different between the W123 and W126 chassis.

The 951 and 952 are the same exact engine except for a few bolt on things for the chassis it is going into.

The below link is from MACH4 when he installed a 952 in his 380SL. he had to change the filter housing because a clearance issue. this will show you the slight difference in the housings.

http://www.peachparts.com/shopforum/2861222-post128.html

I have a 617.951 that was installed in a 80 W116 that used the 617.950, that is going into my 85 300D W123. Also has the 78 or 79 W116 none EGR Manifolds.


Charlie

Just swapping the engine, you would still use the same AC lines.

Charlie

Hi does anyone know which other heads i.e 951, 950, etc will swap onto an om617.952 block? The motor is swapped into a pickup, head cracked and am looking for a replacement. The intake and exhaust are from the .952 motor

The OM617 turbo engines in the W116 300SD had a smaller upper oil pan so it would clear the crossmember, and the 1978-1979 engines had 110 horsepower, while the 1980 model year had 125 horsepower. Also, none of them with the exception of the the California emissions 1980 model year had an EGR valve, so you get nice manifolds with no ugly EGR valve.

https://lh3.googleusercontent.com/xh...e=w800-h453-no

All the heads are the same.
85 heads have a different cam for slightly more horsepower...