1970 280s.......should I?

[1969280s]

Gentlemen,

After selling my 1969 280s a few years ago I swore to myself that I would never again buy a Mercedes with Zenith Carbs. Never say never. After missing the build quality of my 1969 dearly, I have been on the hunt for a 280se that was as nice and relatively local (these cars need to be seen in person). The hunt has been long and difficult. Today I found a perfect and I mean perfect 1970 280s green/green, power roof, A/C that works, heater levers that are new, heater blower motor that is new, crank windows with ZERO rust (absolutely rust free) and 65k miles for a steep yet negotiable $6,500.

My primary concern has always been rust and my secondary concern was to make sure I avoided the temptation to buy another Zenith car ever again. Now, tomorrow I test drive this car and I was wondering how I can tell if any of the carb system is warped, worn or otherwise not repairable like my 1969. If it starts well from cold, doesn't stall, idles well and accelerates well, is that all I need to test. This car is so cosmetically perfect that my impulsive side is telling me to overlook the Zeniths.

My sensible side is constantly reminding me of the utter and total nightmare I had and my mechanics had getting my 1969 to run smoothly and it never, ever did. It seems that there are two things on these cars that cannot ever be permanently fixed, rust and warped or troubled Zeniths. What to do?? And what is a fair price for this car considering it has Zeniths and is not injected?


Best,


David

[JimFreeh]

David,

The mechanical fuel injection comes with it's own set of problems.
Great in it's day, but hard to find someone to service now-a-days.

Why not consider the 280S and replace the Zeniths with Webers?

I've got the Weber conversion on my 250C with the same motor (M130 2,8L) and I could not be happier with the carbs.

At this point, condition should be the overiding factor, not carb or injection.

Jim

[1969280s]

Jim,

Where can I buy a set of Webers and how much will they cost to buy and have installed? Thanks for your assistance.

David

[JMela]

http://www.jameng.com/ sells a Weber conversion kit for $900.

Here's a Zenith --> Weber conversion writeup posted on the JAM site:

http://www.jameng.com/products/pdf/mbca1article.jpg

Page 2:

http://www.jameng.com/products/pdf/mbca2article.jpg

An article on a solex-->Weber conversion on a 220s:

http://www.mbzponton.org/valueadded/maintenance/carbweber/weber.htm

[Blue 72 250]

I would not jump to the webers unless you know that the zeniths are shot. Even then I would attempt a repair. Unless, of course, you have $900 laying around and feel motivated to "stimulate the economy" IMHO

The kiss of death is the linkage bushings on the throttle valves. If there is a lot of side to side slop then you are going to see problems with sync. over the range. Even that is not the end of the world - just going to be less efficient though.(which I am sure the inat is not known for)

If she comes off the line strong and without any hesitation, that is great.(indicates accel pumps working good) If the secondary circuit opens when you punch it, that is great. (rubber diaphram and likely the rest of the carbs have been maintained) If she idles nice and low without any problems, that is great.(most likely not warped).

The biggest problem that INAT's have is people touching them when they don't know what they are doing. (dont ask how I know this)

[pj67coll]

Sounds like she's in good enough shape that the only real problems might be the carbs. But from your description they don't sound like a problem. I'd say go for it. I had a 71 280S. I know what you mean about the build quality. I *will* have another some day. Post pic's sooon as you get her

- Peter.

[Robert Squires]

* I agree with pj76coll. The main problem with the Zeniths (all the carbs for that matter) is service by wing nuts who haven't bothered to FIRST read and understand the carb.
* Nearly all the internal problems are needle and seat replacements and FLOAT LEVEL. If the float level is off just 1mm you'll never get the carb to perform right in all temp and load conditions. Correct float level = name of the game!
* The next common problem is the choke heaters (not getting current) and choke gap, but that's external work. Secondary diaphrams are also external work.
* For all intents and purposes, external adjustments take care of everything else. Section warpage (since the INAT series carb is a multi-layer design) is occationally a problem, but I've generally found something else wrong (like float level) when warpage was blamed.
* It helps to have an air sync tool. Assuming that ALL OTHER ADJUSTMENTS are correct (e.g. cam timing, ignition curve) and you're ready for a final fuel adjustment, set your idle mix to lean-best idle. Then go drive at a steady 3000rpm (in D) for a few minutes. As traffic allows, cut the ignition and coast to the shoulder. Pull a couple of plugs (right where you stopped) to check how they're firing. If they're clean and greyish, you're done. If they're either too dark or bleached white, you'll need to make a small correction to the float level and start over (this is an easier read if the plugs aren't brand new). Another road test is to accelerate briefly up a hill (i.e. full load) at full throttle (you don't need to use top gear and break any speed limits) and note any engine miss. If it misses in this test, you're running too lean and need to adjust the float level.
* Fine carb adjustments are somewhat tedious, but in the absence of a dyno or at least an exhaust analyser, that road procedure will work to get you a very close setting. And you'll probably have the best running 280S around!

[bwostosh]

Buy it ! Everything stock can be fixed cheap.

When referring to "warped" Carburetors,
If there is a detected leak at the base-to-manifold,
or the bowl top leaks,
"hammer-handed" mechanics will over-tighten them,
rather than remove clean, check with machinists straight edge, new gasket and careful torque down.
This gives the owner a warm temporary feeling and an easy hit on the wallet. Bad mechanic trick. You may have to come back in 6 months for the full ream carburetor job. likely over a thou.
Those are amongst the finest carburetors made, check the quality of base castings, (compared to Holly, Carter,etc.) they will out perform and deliver better mileage than any other on this motor.
They have been factory calibrated for this car.
Yeah I have one of those motors too.

I cannot get perfect working exhaust heat risers though,

The carbs must be hot below the throttle to negate the air temp drop and fuel condensing caused by high manifold vacuum.

Adjust valves, check chain, do all the normal stuff, check fuel mileage, ATF in the tank

[ctaylor738]

At that mileage, you should be OK, ASSUMING that the heat risers have not been stuck in the open position and thus starting the process of baking the carbs and warping the top plates.

Sounds like a nice car. But $6500 is all the money for a sedan.

[wbain5280]

Rust free cars are hard to find. Carefully check for properly greased joints and if necessary, take your grease gun along. I helped a young man with his 1961 220b and used my heat gun to soften up the dried grease. The new grease went right in.

I would say buy the car since you are already familiar with them.

[todds]

One thing I like about the INAT design is that the secondaries act like they are mechanical then "become" vacuum controlled when you punch it, right when they need to be thanks to the clever linkage mechanism controlling them. The linkage on side of the carb prevents them from opening too soon and follows directly the action of the throttle under high vacuum. The Weber conversion, having a completely mechanical secondary, bogs for me when punched in certain circumstances. You have to be more judicious, whereas with the Zeniths you can just floor it and not think about it. I think the biggest advantages the Webers have going for them is that they fit perfectly size-wise, are simple, and have a huge aftermarket following and support, whereas the Zeniths have nil. I also think the stock Zenith setup has an advantage with heat management in terms of fuel boiling which the Webers seem to be susceptible to (assuming your heat risers are either working or stuck "the good way"). This is most likely due to the elimination of the fuel return system which most Weber installs delete.

[1969280s]

Thanks for all of your sound and professional advice. I was thinking that $4500-$5000 would be a fair price for a nice 280s, am I incorrect?

David
CT

[cth350]

it's a buyer's market. Try a little lower. -CTH

[pj67coll]

Regarding the price. It's almost meaningless to ask others for their opinion. It's worth no more nor less to you than you are willing to pay for it. These are getting rarer by the day and assuming you will always be able to pick up a good example cheap may be a false assumption. If the cars really good and you really want it what does a couple of thousand matter either way on a 4-6 thousand dollar car?

- Peter.

[Cervan]

Any performance modifications to the fuel injected twincam engine?