Awww c'mon Zeus, deep down inside you miss those Zeniths, admit it. Hell, I love mine, never a dull moment. Figuring out how to keep them running sweet keeps my synapses snapping like they should, and I'm reaching an age when that's damn important...

Now, ask me about that D-Jetronic on my 350SL 4.5, boy I'd trade it for a honkin' Holley any time. Couldn't get any worse fuel mileage, and with no electrons involved, even I can figure the thing out.

Cheers,

230/8

I agree 230/8 - while I may b e driving folks on this board nuts with my questions, I enjoy learning.

The vacuum from my zeniths is manifold vacuum, so I now have advance vacuum at idle, goes away upon initial accelration and then increases to a steady point at driving speed. I asked this question earlier but I don't think there is a ported vacuum source on this car. I did set the timing then with the vacuum advance hose connected.

This approach has not completely fixed all of my problems though. From a cold start, choke closed, car runs fine - no lurch and no backfire. As car warms up, periodic lurch and backfire there (too much air or too little fuel present as choke opens??), once car reaches operating temp, tends to run better - still a slight hesitation but no carb backfire. Overall though, car is definitley running better with much better mileage.

I do have the tools (and all of the manuals) and I think the carbs are balanced well - although considering my persistent symptoms, I would suspect that something is still not quite right with them.

ryan

__________________
RG Newell

1984 300D
1972 250
1986 560SL
1991 300CE

I guess my final suggestion would be to try re-timing the engine w/o the vacuum connected then hook it up to see how it runs. Remember, if you have vacuum advance at idle then leaving it connected while timing will give you a false reading and too little total mechanical advance when you need it and too little total advance at road speeds. In other words, there is still a potential for "late timing" which is usually gives you a symptom of an off idle stumble.

Remember, the two advance mechanisms are intended, in a normal vehicle, to work together. Under full throttle the vacuum is not advancing the timing so the centrifugal advance controls the timing and is designed to provide an optimum amount and rate of advance for full throttle conditions up to maximum engine rpms. At lower engine speeds and at part throttle the centrifugal advance will provide only a part of its potential advance range so the vacuum advance is there to provide that little bit extra needed for good performance and fuel economy.

Keep at it, you are solidifying your knowledge of some important principles and also learning how your specific engine responds to changes in basic settings.

230/8

lol...I do miss them a bit actually. I enjoyed working on that engine...so simple. It was satisfying when you'd do an entire tune-up - replace points, rotor, plugs, clean and de/re-assemble carbs, etc. - and you'd finally get the the whole thing running perfectly. I rebuilt the upper half of that engine as well. Learned a lot doing it. Should help when the 300E needs the head done...

__________________
Chris
2007 E550 4Matic - 61,000 Km - Iridium Silver, black leather, Sport package, Premium 2 package
2007 GL450 4Matic - 62,000 Km - Obsidian Black Metallic, black leather, all options
1998 E430 - sold
1989 300E - 333,000 Km - sold
1977 280E - sold
1971 250 - retired

"And a frign hat. They gave me a hat at the annual benefits meeting. I said. how does this benefit me. I dont have anything from the company.. So they gave me a hat." - TheDon

My 280S had the same symptoms, found broken advance weight spring in dist. base, replaced springs, adjusted them so full mechanical advance comes in at 2000 rpm, installed Crane Cams Optical Conversion kit like you have, disconnected the vacuum RETARD hose to the dist. advance unit and plugged it off, set base timing to 20'BTDC with ADVANCE vacuum hose disconnected, (before TDC, not 4' after TDC with hoses connected as shop manual states), AND THEN synch'd the carbs and set to 600 rpm in drive.

NOTE: DO NOT REINSTALL THE CONDENSOR SCREW ON SIDE OF THE DISTRIBUTOR AFTER POINT CONVERSION AS IT WILL HIT THE ADVANCE WEIGHTS IN THE DIST.BASE WITHOUT CONDENSOR BRACKET IN PLACE!

Can now spin the tires from a dead stop, runs great w/93 Octane fuel and doesnot ping!

Note: are both idle shut down solenoids powered up correctly?? with key on

Hope this helps