Hello everybody. I have a 1985 300SD. I bought it cheap cause it had a busted head due to lack of antifreeze during a cold winter. I got a replacement head from a scrap yard for $30 that I still haven't put on yet. Thats just my intro and not what the post is about.

I am trying to find some info on the pistons and rods in the early 300SD. OM617.951 I think. I have been searching and searching and can find nothing. Are the pistons aluminum? Are the pistons and rods cast or forged? What is the rod journal size? What is the rod length? What is the pin height? Overall how strong are these rods and pistons? Thanks for your help everyone.

Not sure. but replacements are pretty easy to come by both new and used.

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hum.....
1987 300TD 311,000M Stolen. Presumed destroyed

Thanks. Getting the pistons and rods is not the problem. I need to know the dimensions, if they are forged, and how strong they are.

ALL OM617 parts are forged...

From pure awesome...

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My occupational hazard bein'
my occupation's just not around...
1980 300SD
1980 300SD

Blasphemy. I heard man could not yet harness the power of awesome. Tricky Germans.

There is a SAE report about the development of the 617 turbo. It goes into the development of the internals.
There is some very unusual metallurgy involved. Best not messed with. They destroyed a lot of 617's in the development of the turbo.

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Grumpy Old Diesel Owners Club group

I no longer question authority, I annoy authority. More effect, less effort....

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.
1968 Ford F750 truck. 6-354 diesel conversion.
Other toys ~J.D.,Cat & GM ~ mainly earth moving

The pistons are aluminum and because of the complicated shape must be cast. The rods and crank are iron I believe.

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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.

You'll find loads of specifications in the factory service manual (FSM)

Chapter 3-316 "removal and installation of pistons"

More info:-

You'll also find that there are three official group sizes for the pistons (over bore sizes). A machine shop / engine re-builder will have a universal source of information that carries specifications for "all" engines.

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1992 W201 190E 1.8 171,000 km - Daily driver
1981 W123 300D ~ 100,000 miles / 160,000 km - project car stripped to the bone
1965 Land Rover Series 2a Station Wagon CIS recovery therapy!
1961 Volvo PV544 Bare metal rat rod-ish thing

I'm here to chat about cars and to help others - I'm not here "to always be right" like an internet warrior



Don't leave that there - I'll take it to bits!

Thanks for the info. I was asking cause I was thinking about using them in a turbo gasoline engine application. I was trying to figure a strong set of rods/pistons I could get from the scrap yard and diesels are probably the only things forged there. Cast pistons don't seem to tolerate detonation well. I was thinking if they handle 21:1 plus boost they might be able to handle 8.5:1 plus boost. 8.5:1 with 20psi in a gas motors give about 20:1. Any thoughts on this? Thanks again

OK fair enough.

I'm not going to comment on what is good or not good to do as I don't know.

Perhaps getting in touch with layback40, whunter, vstech, mbdoc and engatwork would be a good idea? May be one of these guys could help.

If not try the contributors on www.superturbodiesel.com

BUT I've asked some questions about my OM617 NON turbo engine that may be of use:-

OM617 piston ring installation question

Piston ring question

But best of all some dimensions are given in a pdf file in post #6 of this thread

OM617 connecting rod weight colour codes

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1992 W201 190E 1.8 171,000 km - Daily driver
1981 W123 300D ~ 100,000 miles / 160,000 km - project car stripped to the bone
1965 Land Rover Series 2a Station Wagon CIS recovery therapy!
1961 Volvo PV544 Bare metal rat rod-ish thing

I'm here to chat about cars and to help others - I'm not here "to always be right" like an internet warrior



Don't leave that there - I'll take it to bits!

Yeah, I saw those threads. I was looking for length info to figure compression more so than weight. But if the pistons are cast they probably won't take much detonation or boost. Thanks for all the quick replies. Anyone have any more info?

Not happy yet eh?

Well you've got bore data from those threads and the stroke for all 240D - 300D - 300DT (617.952) engines is 92.4mm

I can confirm that in the SAE "development of the OM617a" technical paper mentioned by layback40 they state that the pistons are cast. Here it also says the wrist pins were enlarged to 28mm for the turbo engine. Haynes states non-turbo pins are to be between 25.995 to 26mm and the turbo pins are between 27.995 and 28mm. The turbo pistons have an extra gallery in the casting used to help with heat dissipation.

This paper does state that they had problems with cracks forming in the piston crowns close to where they built in a recess for the pre-chamber that protrudes into the cylinder. This was fixed by adding small radius edges in the design.

If you decide to use these pistons in a petrol engine are you planning to remove these recesses?

__________________
1992 W201 190E 1.8 171,000 km - Daily driver
1981 W123 300D ~ 100,000 miles / 160,000 km - project car stripped to the bone
1965 Land Rover Series 2a Station Wagon CIS recovery therapy!
1961 Volvo PV544 Bare metal rat rod-ish thing

I'm here to chat about cars and to help others - I'm not here "to always be right" like an internet warrior



Don't leave that there - I'll take it to bits!

late 80's early 90's 302 H.O. Fords are forged and can take about 14 PSI stock. Put 100,000 miles on a turbo 5.0 before I sold it. Still ran like new. What gas block are you using?

Obviously being in diesels, the pistons can withstand pretty high compression. I would be curious in seeing their performance in a gas application, as obviously they were designed with diesel combustion in mind. Typically diesel pistons have a double-inverted cone shape on the top, but these OM617s have a surface typical of gasoline engines so it might just work.

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TC
Current stable:
- 2004 Mazda RALLYWANKEL
- 2007 Saturn sky redline
- 2004 Explorer...under surgery.

Past: 135i, GTI, 300E, 300SD, 300SD, Stealth

Right. I had mustang with em. The thing is that they are a 4" bore. I was thinking about a junkyard build. And the OM617 has a 3.57 bore. That is the same as a .020 over 4.6/5.4 modular motor. The stroke is almost identical to the 4.6. I couldn't exactly pin point the rod journal size for a OM617 but I think its 1.88 which a forged mod crank can be turned to. Offset grinding could take care of differences in deck height and control how far the pistonn is in the hole for compression reasons. As I was contemplating a JY build I figured the only motors in a junkyard with forged rods and pistons would be in a diesel. After looking at 7.3 IDI I saw the rods were to long at 7.1 or so. I also consider the 6.2 Chevy but info is scarce.

Since I have a local scrap yard with a couple 300SD I know I could get the rods and pistons for less than $100, maybe like $50 probably. But if the pistons are cast it really would be a waste of time in a boosted app.