I thought that I would start a new thread to cover the engine swap I am about to do in my 1991 350SD. I wanted to have a title that would be easily found by anyone searching the forum for information, as I have been doing for the past several days. I know several forum members have made this change, and I hope you'll add your most recent wisdom on the topic- Thank you!


Just to set the table, I have a 1991 350SD with a OM603.971 that has done its bit to earn "rod bender" status. After reading about the experiences of others here, and benefiting from your advice I have decided to install a 3.0 litre OM603.960 engine from a 1987 300SDL. The new engine is currently in a Chevy Tahoe and seems to run well, albeit with a thin wisp of blue-grey smoke while running. It shows good oil pressure, has a little blow-by, not bad in my observation with oil filler cap removed. The seller claims a mileage of approximately 143k miles, and oil consumption rate of 1.5 quarts over 4k miles.

My plan for this engine is as follows:
To disassemble and assess condition of the short block. My observations on disassmbly will be my guide, but I am primarily interested in the cylinder bores, and the suitability of simply installing new rings to ensure good compression and low/no oil consumption.

Since there have been reports of a few 603 3.0 engines tossing a rod, I'll be looking at those closely as well.

Once the health of the block has been established, I will be installing most of the rest of my 3.5 litre engine, as much of it is essentially new, with very low mileage. The major pieces will be the oil pump and oil pan (less windage tray), #22 cylinder head, turbo and injection pump.

Which brings me to my first question-

I have read that the 3.0 litre has a higher rev limit, and actually generates some useful hp there. I would like to bring my 3.5 IP to the injection shop and have the governors rev limit set to accomodate that. Where would I find the proper specifications for that? I don't see it in my MB 602/603 service manual.

Also, thank you for reading and contributing. I think back to years ago working on cars literally "in the dark." This forum makes tackling a project like this worthwhile!

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Chief

1991 350SD

why don't you just leave the .96 IP in place?

__________________
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!

Why not run the .96 IP since it's already matched to the displacement and rev capabilities? The cost of modifying the .97 IP might as well go to refurbishing the .96 IP.

Reconsider your turbo decision. The 55 trim .97 turbo will take longer to spool, at least theoretically. You're already at a torque disadvantage with the .96. My 93 SD 3.0 with 55 trim turbo was okay but the bent rods and smokey .97 pulled harder off the line.

Check the oil pump mounting carefully if you remove the windage tray. The .97 oil pump aft mounts stand off the main cap by the thickness of the windage tray washer. You should replicate that thickness if you run without the windage tray.

Check the sequence number, 7th and 8th digits of the part number, of the front cover/timing chain cover. You can only compare if the other numbers are the same. MB strengthened the area where the belt tensioner arm attaches. I've seen 3 variations.

Consider which damper to use. Someday I'll compare .96 and .97 damper part numbers. Meanwhile, the thread on the definition of 'neutrally balanced' is contentious

Sixto
87 300D

The .97 IP has already been serviced at the Bosch FI shop, whereas the .96 is an unknown. Since every dollar counts, it's either run the .96 as it is or have the governor adjusted on the .97.

A previous thread mentioned the .97 turbo MIGHT offer a slight gain in power. Physically, as I understand it the .96 turbo and plumbing are slightly longer, and won't necessarily fit up with my existing air box bits. Since I have none of those components from the .96, it seems easier to use the .97 unit. Also, it was new 30k miles ago, and the .96 unit is an unknown. If these two choices won't hurt performance or create driveability issues, I'll stick with them.

I plan to use the .97 timing cover, but will look at the numbers to verify if it's an updated reinforced version.

Good points about the oil pump and damper! I haven't read anything that suggests the windage tray offers any benefit, but can lose it's mounting screws. In fact, that had previously happened in my .97. If there is a benefit, I can always safety wire the mounting hardware.

I hadn't considered the damper- I'll check out the thread!

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Chief

1991 350SD

Your driving habits will dictate. I didn't notice the .97 IP to be an impediment since I don't rev beyond 4000 rpm. You might be better off leaving the governor as is and adjusting the full load stop for power at, IMO, more useful rpms - Injection Pump fuel adjustment for the MW and M pumps, pyrometer install - Mercedes Forum - Mercedes Benz Enthusiast Forums

Before you adjust the IP governor, check with someone who knows how the transmission will react. Theoretically, it'll be programmed to shift at the .97's redline, not the .96's. TC stall might be a factor but I didn't notice any problems with the 93 SD 3.0 running the car's original transmission and TC... not that I can confirm they were the orignal transmission and TC when I got the car. The .971 block serial number didn't match the data card.

An intake snorkel from an 86-87 SDL shouldn't be difficult to locate if you stay with the 50 trim turbo. I don't know if an intake snorkel from 87 300D/TD is an option. Given your clarification, I'd stick with the 55 trim.

Sixto
87 300D

I'm doing something real similar this week. I'm putting together an engine out of an 87 E class diesel into a 91 350SDL. I moved the oil pan from the 91 to the 87 today and kept the original oil pump. I did not see where there was enough difference between the two to cause an issue.. I will say the 87 oil pan will not fit the 91 engine because the of interference between the windage tray and the guides in the pan.

There is a big difference between the weight of the 91 flywheel and the 87 with the one in the 87 being a good bit heavier.

Hopefully, I will get it back in the car tomorrow.

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Jim

Good luck with it!

Which flywheel are you using?

And Sixto, I like your comments on the IP.

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Chief

1991 350SD

I think it would be interesting to try the lighter flywheel on the 3.0 L engine but I'm not going to do it. I'm sticking with the stock flywheel and IP on the 3.0 engine. The only things I've used so far off of the 3.5 engine is the engine mounts and oil pan.

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Jim

Engine bolts up just fine with the 87 300D cars flywheel. The larger oil pan would have worked out fine. I recruited the lovely Mrs engatwork to help me lower the engine into the car. She said she did know know how she got her hands dirty. She stays on top of that seeing as how she is a nurse.

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Jim

I don't know man, they don't make horror movies about people with greasy hands

Sixto
87 300D

That's good info Jim, Thanks. I already have a buyer for the '87 oil pan, so I'll be sticking with the '91.

You have me thinking about the flywheel. Given that the 3.0 engine I am buying is still in the Chevy Tahoe, I don't know what is there for a flywheel, and whether it may have been modified for use in that application. Do you foresee any problems using the lighter .970 flywheel? Are there any balance issues?

Nice to have a wife that doesn't mind pitching in to lend a hand!

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Chief

1991 350SD

That is a good question. The factory service manual tells you that if you replace the flywheel you do have to balance it to match the one coming off. It would be interesting to see how the 300D engine would perform with the lighter flywheel. If I only had an engine dyno.

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Jim

I'm bringing home the OM603.96 engine tomorrow, and disassembly will begin. I have already ordered and received all new gaskets, cylinder head bolts and flywheel bolts. I have a couple questions about what else I should have on hand.

1) Rod and Main Bolts.

I know tha FSM has diameter specs on these to determine their re-use. I was curious as to the experience of anyone who has rebuilt one of these. Should I just plan to buy all new bolts for the piece of mind that bring?

2) Piston Rings

Like everything else for these engines, these are friggin expensive! Peachparts doesn't list them; ******** AZ claims to have Deves rings at a very reasonable prce, but they are not in stock. Any recommendations on brand, and where to buy?

3) Vacuum Pump

Since I'll be building this from the block up, would it make the most sense to install a new pump now? Both pumps on both engines work, but I'm sure they are both original.

4) Bearings

Any favorites out there for this engine?

Thanks!

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Chief

1991 350SD

2) MB list for a ring set is $134. Cheaper than aftermarket at the AZ place... unless that's $134 for each piston FastLane has .96 rings but you have to enter by part number and it returns Goetze brand for $46. Oddly, FastLane only recognizes the original part number 002 030 03 24 which has been superseded twice to 003 030 11 24.

3) If you have to ask...

You're changing everything else, how about the chain drive?

Sixto
87 300D

Yeah, those prices are per cylinder!

The ******** price was for all 6.

Even tho the chains and rails only have 35k on them, I'll be replacing them, and yeah I guess I should do the vac pump. Wish I could save a buck or two somewhere on this project!

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Chief

1991 350SD