Zenith. Stromberg, Weber - Help

[meltedpanda]

My 71 220 has a strombeg (175)
I am trying to find info on line on repair, adjustments. Is there any similarity between the Zenith or Weber. I seem to be able to find more info on those models

[Mark DiSilvestro]

Other than they're all carburetors, not much.

The sidedraft Stromberg has more in common with the carbs used on countless motorcycles and British sportscars.
The Zenith and Weber are fixed venturi designs, while the Stromberg has a variable venturi, operated by that big diaphragm I mentioned earlier. Unlike the others, the Stromberg uses a cold-starting valve instead of a choke. My May 1970 114-115 factory service manual has some pretty good information on the more basic early W115-220 175CD Stromberg with a cable-operated cold-start valve, but your '71 should have a water-heated automatic cold-start valve and electric fuel cut-off valve attached at the bottom - details that aren't included in my manual. If you can't find a later issue Mercedes factory service manual on paper or CD, The CD series Strombergs were used on '60s Triumph sportscars. Maybe a Triumph manual can give you a basic idea on how the Stromberg functions.

Happy Motoring, Mark

[rs899]

Look around in the Triumph world for Zenith Stromberg info. I don't know exactly how similar they are to what I had on a TR-7 and TR-6 I had, but I found them a major PITA. I have successfully forgotten most of the bad points on these puppies. I still have one on my Spitfire, but that will be replaced with twin SUs (same idea- much better in execution. I think Zenith copied SU but had to modify to avoid patent issues.) or a sidedraft Weber.

There may be some good data here: (look under technical, then TR6-TR250 carbs)


http://web.archive.org/web/20020605024956/http://www.buckeyetriumphs.org/

If these have a water choke, you may want to find a way to convert to manual as they commonly corrode and go nonfunctional. Better yet, maybe you can replace it with an SU (HS4 should bolt up, I think). Good luck .

Oh, methinks I MIGHT have a Haynes Zenith Stromberg manual at home I can part with now if you need one.

[meltedpanda]

Thanks again,
I do have the two coolant lines into the front of the carb and a wire connection to the bottom, just like you mention Dave.
Going to be turning her over soon and just wanted to understand how the blasted thing works. Looks like an overgrown mushroom of some sort and really has me a bit baffled, I am use to "normal" looking and functioning carbs.
Thanks RS for the link, if you think your manual will help me , PM me and we can work out the details
Learning as I go

[rs899]

The carb function isn't "normal" but it is pretty good in theory. If you peer into it from the outside you will note a brass needle that moves (or should move)up and down. At the bottom of this needle is the bowl. As the needle rises (more vacuum) more gas is sucked in from the jet (the hole where the needle seats at the bottom). Problem is the bowl gets full of crap , float needle doesn't seat, leaks etc. Also, on the Zenith you have to remove the carb to clean the bowl. That is, IF you can get the bloody big brass screw loose in the middle of the bowl. And then there is the crappy water "choke" , and the temperature compensator and emission add ons that fail with age. And the rubber diaphragm that fails.

The SU, on the other hand, is an elegant, simple design. Very similar. Except the float bowl is on the side and has three screws on top- can be cleaned in 2 minutes. Has a choke that effectively raises the level of the fuel in the bowl for easier starting. No diaphragm. Maybe 3 moving parts. Piece of English cake.

Well, that's probably more than you (or anybody ) wanted to know.

[Mark DiSilvestro]

Another thing to check - the Stromberg is mounted to the intake with a bonded-rubber insulator and I've seen the aged rubber split, causing a major vacuum leak.

Note that Zenith may have built these sidedraft carbs for Mercedes under license, but to avoid confusion with the 'regular' Mercedes carburetors, I like to refer to these sidedrafts as a Stromberg (or 175CD)

Happy Motoring, Mark

[meltedpanda]

yes mine is marked 175CD, now the obvious question
parts, seals, rebuild kit ect where does one locate them??

[rs899]

I would say if you can't find it in the usual Mercedes places, try the Britcar suppliers.

The Roadster Factory
Moss Motors
possibly British Parts Northwest (he'll be cheapest)

But, what to ask for from the Britcar suppliers? For a rebuild kit, I would look for one from say, a 1980 TR7. That would probably be the most complex and most likely would have the most dizzying array of smog stuff, and you should be covered. Your needle will be different (width/profile of the needle changes by application) but you probably won't get one anyway in a basic kit.

Are these British-made Zenith Stromberg 175CDs or were they made by MBZ or somebody else?

Rick

[Mark DiSilvestro]

As I recall, the Mercedes Stromberg was German made, hence my 'made under license' comment. Have you tried Phil here at PartsShop?

Happy Motoring, Mark

[meltedpanda]

Yes mine says "made in Germany" I want to turn this baby over but now I am faced with some loose lines as well as another issue
1) there are two dome looking units mounted on the fender well (passenger side) that have four lines running from them (or did have) . One has a line going to the distributor the other line is missing. The other has one line going to the carb and the other line is hanging there unconnected. There is one port on the carb that does not have a line. Problem is which goes where
2) I want to by pass the gas tank for this initial start but there appears to be two fuel lines into the front of the carb. One comes from what appears to be the fuel pump the other goes into the bowels of the car and I can't figure where it goes? The fuel tank I suppose ?
3) what is the purpose of the electric fuel cuttoff valve??

RS, the info on the triump site is helpful except most of it is greek to me.
I continue to plod along, thanks again

[Mark DiSilvestro]

Plug any open fittings at the carb or intake manifold, then forget those 'dome things' for now. They're vacuum advance/retard controls for the distributor and the engine should at least start without them.

The line that goes 'into the bowels' is the fuel return line and eventually connects to the gas tank.
You need to connect an auxiliary gastank to one of the lines that connect to the fuel pump. Either hook the aux tank to the fuelpump inlet nipple and hope the pump still pumps, or suspend a small tank, such as a lawnmower tank, above the carburetor and connected to the carburetor inlet nipple so it can feed gas by gravity.

Before going through all this, you should first see if it will crank over. If it does, then have someone crank it and see if you have spark at the coil or a plug wire. If there's spark, before rigging up a gastank, you could try some starting fluid in the carb throat.

The electric fuel cut-off valve shuts off fuel to the main carburetor jet when you switch off the ignition, It's to prevent run on or dieseling after shut-off.

Happy Motoring, Mark

[rs899]

Melted

Mark is right. First look for spark, then worry about the fuel aspect. If you can at least get it to run briefly on ether, then you can concentrate on the fiddly carb.

Yes, a Zenith Stromberg will look Greek to you , until you open it up. Still will be odd functionally. Some of these were pretty adjustable carbs, some weren't. As you get into it, try to figure out if the needle on yours is adjustable. Hopefully , you will be able to vary the mixture by moving it up or down relative to the piston it is attached to on top. The other big "if" is the float bowl- can you get into it?

Let us know

Rick

[meltedpanda]

Can't thank you enough, only wish you lived next door
going to be out the next few days but will keep you all posted.
I removed all seats and carpets last night ( for eventual cleaning) to get a good look at the floorboards - everthing is great no rust , solid
Thanks again

[Mark DiSilvestro]

With the Strombergs on both my '67 Sunbeam Alpine and the '72 220 that I used to have, the mixture was adjusted by rotating the needle's seat or jet assy which protruded from the bottom center of the float chamber. In the case of the 220, I had to loosen a locknut, then turn an adjusting nut which rotated the whole jet and cut-off valve assembly enough to lean or richen the mixture. Once adjusted, the locknut was retightened. As I recall, the locknut and adjuster took a 19 MM open-end wrench.

Happy Motoring, Mark

[vox_incognita]

http://jaimekop.com/CarbManual/index.html