M121.940 vs. M121.941 - PeachParts Mercedes-Benz Forum

kelf · #1 07-07-2002, 03:43 PM

Hi again,

This engine that is so badly stuck is a 1966, M121.941 . It's in an O319 - pictures are at http://www.geocities.com/mb319camper , including pictures of the engine number plate and the inside of the cylinders and head.

My understanding is that the M121.940 appeared in the 200-model car of the same year. But I'm assuming there is some modification of the 940, for use in a commercial vehicle, that resulted in the 941 designation. Where could I find out what this difference is?

I'm thinking I might want to just overhaul the head I have and find a rebuilt short block for a M121.940 . But this vehicle is notoriously slow and underpowered anyway, so if they did any tweaks in the 941 that helped, I'd like to keep them.

Apreciate any insight...

Kelly

skalie · #2 07-08-2002, 03:45 AM

http://www.jordanwinthrop.com/mercedes/models.html seems to confirm your motor info.......

I put a car motor (diesel) into my oldtimer camper, the 306D.

It involved changing over everything, even the oil pan to get the dipstick in the right position.

The bearing in the gearbox at the end of the flywheel was also different (front wheel drive), engine mounts, manifold etc., etc.,

The oil filter still needs to be moved and burns my right foot instead of hanging under the engine, had to cut a hole in the engine cover.

If I had your bus, in my town, I would be going down to one of the local scrapyards with relative confidence that I would find something that would fit in.

I would also be completely confident that the slow and underpowered factor shall remain.

Mark DiSilvestro · #3 07-08-2002, 10:23 AM

In my book'Mercedes-Benz Production Models - 1946-1975' I found engine #121.940 listed for 200 series fintail cars through feb 1968 but no listing for #121.941.
The 200 fintails had dual carbs and were rated at 95 HP.
Does your 319 have dual or a single carb?
That may account for the number difference.
There were number variations listed for some of the other engines depending on compression
ratios and number/type of carbs.
Also some variations in numbers due to location of motor mounts. For example - ponton engines had mounts at the front of the block and fintails had them at the side of the block. Hope this helps.

Happy Motoring, Mark

cth350 · #4 07-08-2002, 02:35 PM

There is no way to figure out exactly what's different between a 121.940 and a 121.941, other than to walk through the relvant parts book. I have about 1,000 sheets of euro truck fiche which is unsorted. Perhaps the relevant film is in the pile.

But, if you start comparing the motors, take notes so that the next sucker, er um, the next poor soul in your situation isn't as stuck as that motor.

Put a more recent 4 cylinder in. A mid-70s 230.4 (M115) or a snazzy M102 should be worthy. If you have to use the original transmission, then an M102 w/5-speed sounds like its out of the question.

-CTH

ctaylor738 · #5 07-08-2002, 04:43 PM

My $.02.

I replaced the M130.923 engine in my 1972 250C with a M130.920 out of a 1969 280S. The only differences I could find were extremely minor - no coolant sensor for the rear choke, oil cooler installed, etc.

So you would probably be OK with a 940 engine. I would vote with Mark that it's the single carb.

kelf · #6 07-08-2002, 09:18 PM

The M115 is sounding like a nice way to go. I've been looking on the web for pictures of it, and what I've seen so far shows an intake manifold that stretches out to the side, with a sidedraft carburetor (or carburetors) that goes further to the side.

On this engine, the manifolds are really narrow, with a single updraft carb on top, so it all can fit between the footwells. (Hopefully there's a picture attached below, and this one and other engine compartment pix are at http://www.geocities.com/mb319camper/engine.html .)

I'm guessing these manifolds could be bolted to the M115 head, but would that little carburetor be strangling the 2.3L? Might there be a way to modify the 2.3 intake and bring its carburetor out to the front a little? (I'm seeing a long tube between the carburetor and the intake, and a right-angle turn, and a choke that you can never quite open all the way...)

Mark DiSilvestro · #7 07-08-2002, 10:28 PM

It looks like, from one of your engine photos, that your motor mounts are at the front of the engine block. If you find a replacement engine, make sure it has the threaded holes for the motor mount brackets.
As to replacement carbs, if your 200 manifolds will bolt up to a 220/230 M115 engine, you could try to find a twin carb intake from a '65 to '68 200 fintail. Also the '59 to '61 ponton 190b used a single compound 2V Solex carb. If that intake would interchange, you might fit a holley/weber 2V such as used on the '70s 2.3L Pintos.
I have a 1969 Chilton Mercedes book that shows a twin carb manifold on the early M115 4 cyl 220. This might be an easier swap if you can find one. Note : the M115 220 exhaust manifold/header pipe is different than yours.
Happy Hunting and
Happy Motoring, Mark

kelf · #8 07-10-2002, 10:23 PM

That twin carb ought to be great for getting more power into this thing. Just wanted to confirm - would it fit in the space available here? It's about 4 1/2" from the port surface of the head to the egde of the passenger compartment. The left side of the picture shows the view from the front, and the right shows it from the rear/top. Any idea if the manifolds & carbs you mentioned would squeeze in?

Mark DiSilvestro · #9 07-11-2002, 12:57 AM

Well, I just happened to have a 1V Solex carb, intake and exhaust assembly off a 190c fintail and, unfortunately, that unit requires about 7 inches from the head mounting surface, so I'm afraid you're stuck with that, really narrow, carb and manifold setup. I'm sure that the 2V ponton setup would require at least that much clearance.
If your manifolds will fit onto a 220/230 4 cyl, maybe that carb could be re-jetted or you could adapt a 1V carb from an early '60s Ford Falcon. I think the earliest Falcons had a base 6 cyl engine of 140 cid which is about 2.3 liter. Some of the early Chevy Vega 2.3 liter fours also used a 1V carb. then again, we don't know if the later engines will bolt up to your tranny. It may turn out to be the least hassle to just go with a rebuilt 2.0 liter.

(If only you could drop in a 450SE engine!)

Happy Motoring, Mark

Mark DiSilvestro · #10 07-12-2002, 06:58 PM

I took my 190c carb and manifolds over to my neigbors' and measured them against the ones on his '72 220 4 cyl and the spacing and dimensions appear to be the same - about 17" length at the exhaust manifold and about 4" across the center exhaust branch where it bolts to the head. I can't tell if the internal port sizes are the same. Maybe your manifolds will bolt up to a 220/230-4.

Happy Motoring, Mark

kelf · #11 07-16-2002, 11:10 AM

Thanks, Mark, for checking that out. I found a junkyard not too far away that specializes on foreign cars - hoping to get there this weekend to see if they have an 4cyl gas engines.