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  #1  
Old 05-31-2013, 03:10 PM
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1971 250C Vacuum Advance

Any suggestions where I might find one?
Below is one for a 1971 220 on ebay, but the number stamped on it (923) is different from the "825" on mine, suggesting incompatibility. They sure look the same, though.

http://www.ebay.com/itm/NOS-Bosch-Mercedes-220-w115-Distributor-vacuum-advance-unit-0001582718-923-M115-/

I'd prefer a single port version, as my emission controls are incomplete/disconnected.
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  #2  
Old 06-03-2013, 12:27 AM
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Despite the fact that it has been said you can go to the Mercedes STARTEK site and get on the EPC to look up parts I have been using one of the Russian Part Sties (in Engilis).
Pick car, wait till the next page opens; then pick Motor and click on you Motor number type.
Once you have the part number you can use that to shop around.
Russian part site:
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  #3  
Old 06-03-2013, 12:55 AM
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I went to the parts site and it is kind of slow. listed under Electrical Equipment.

There is 5 different ones listes as "Vacuum Box". As you go acrossed to the Right from the Part Number you will see numbers in sort of Brackets. Those are notes and it will tell you what Engine Number or Chassis range uses that part.
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  #4  
Old 06-03-2013, 05:53 PM
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Quote:
Originally Posted by Diesel911 View Post
Despite the fact that it has been said you can go to the Mercedes STARTEK site and get on the EPC to look up parts I have been using one of the Russian Part Sties (in Engilis).
Pick car, wait till the next page opens; then pick Motor and click on you Motor number type.
Once you have the part number you can use that to shop around.
Russian part site:
Thanks D911;
Your link doesn't appear to work.
I tried it without the dash and got a Russian site, but don't see how to view in English, & see no W115 listed under Mercedes.
Am I missing something?
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  #5  
Old 06-03-2013, 06:23 PM
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If your emissions controls are in-operative then why bother with the vacuum advance? Look around for a hot rod shop with a distributor machine (usually a "Sun" model) and have them set the distributor for mechanical advance. Probably costs under $50 and resolves the vacuum issue. You want 30 degrees total at 3K rpms.

Vacuum retard is a different story.
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Old 06-03-2013, 06:34 PM
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If you intend to keep your emission controls in a disabled state, the functionallity of the vacuum box may be academic. Typically it was used only to provide idle retard, or to keep ignition below full advance in the lower gears, with full advance available in 4th. If vacuum is simply not supplied to the box, it then serves only to position the breaker plate, with advance provided centrifugally. Does your current vacuum box hold the breaker plate in place properly? If so, that may be all that is required.
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Old 06-06-2013, 06:58 AM
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Originally Posted by Frank Reiner View Post
If you intend to keep your emission controls in a disabled state, the functionallity of the vacuum box may be academic. Typically it was used only to provide idle retard, or to keep ignition below full advance in the lower gears, with full advance available in 4th. If vacuum is simply not supplied to the box, it then serves only to position the breaker plate, with advance provided centrifugally. Does your current vacuum box hold the breaker plate in place properly? If so, that may be all that is required.
The distributor doesn't have anything resembling the mechanical advances I've seen on others. Without mechanical/centrifugal advance, doesn't the vacuum provide the only advance, which is necessary for optimal performance & fuel efficiency?

The existing vacuum box does hold the breaker plate properly. I've replaced the twin Zephyrs with Webers & I'm not interested in restoring the emission controls...just peak performance.
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Old 06-06-2013, 12:14 PM
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Upon removing the distributor cap, you should be able to turn the rotor (in the direction of rotation) about 15 degrees against spring force. The centrifugal advance weights and cams are located under the breaker plate, and are not visible until the breaker plate is removed from the distributor.
In the event the rotor cannot be rotated, or does not have any restoring spring force, the distributor is a candidate for overhaul.

With a timing light installed, there should be visible displacement of the timing marks with increasing RPM. No movement? Distributor overhaul.
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Old 06-07-2013, 12:17 AM
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Quote:
Originally Posted by Mike D View Post
If your emissions controls are in-operative then why bother with the vacuum advance? Look around for a hot rod shop with a distributor machine (usually a "Sun" model) and have them set the distributor for mechanical advance. Probably costs under $50 and resolves the vacuum issue. You want 30 degrees total at 3K rpms.

Vacuum retard is a different story.
Mike, what does the hot rod shop do when the "set" the distributor? Can they alter the amount of advance?
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  #10  
Old 06-08-2013, 01:30 AM
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>The distributor doesn't have anything resembling the mechanical advances I've seen on others

I must have mechanical advance. Vacuum advance is for economy - it advances the timing at light load (like freeway cruising) to get better economy. On my other car a non-working vacuum advance will cost 1-2 mpg.

Csaba
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  #11  
Old 06-08-2013, 10:05 AM
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When they run the distributor on the machine they change the rate of advance by replacing the springs. They'll give you a diagnosis of the condition of the mechanical parts. Depending on the shop they can alter the amount of advance but that takes someone who is willing to spend the time.

I wouldn't worry about reducing the advance. When the distributor is "right" then the 30 degrees built into it will be sufficient for the car.
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  #12  
Old 06-14-2013, 10:32 AM
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Quote:
Originally Posted by Frank Reiner View Post
Upon removing the distributor cap, you should be able to turn the rotor (in the direction of rotation) about 15 degrees against spring force. The centrifugal advance weights and cams are located under the breaker plate, and are not visible until the breaker plate is removed from the distributor.
In the event the rotor cannot be rotated, or does not have any restoring spring force, the distributor is a candidate for overhaul.

With a timing light installed, there should be visible displacement of the timing marks with increasing RPM. No movement? Distributor overhaul.
Sounds like the distributor is a candidate for overhaul, as the rotor can't be rotated (as above) and, with a timing light installed, there is no displacement of the timing marks with increasing RPM. Thanks for the input.
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  #13  
Old 07-13-2013, 01:16 PM
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I have a '72 250C with the M130 engine and a bad vacuum box. It works in retard, but the advance side has a bad diaphram. The retard/advance at different temperatures and/or RPM's was an early attempt to reduce emissions, which added additional temperature switches, relays, vacuum switches, a RPM switchbox, a relay switchbox and a host of vacuum lines. At least you eliminated the 'throttle valve lift' by replacing the Zeniths with Webers.

I have been trying several 'non-emission' distributors and so far the best one has been from a non-emission 280S. I am using the specs for dwell, timing, etc. for that engine. Tomorrow I have a friend coming over that is helping with this, as well as dialing in the Zeniths. Once everything is set, I will post the results.

Have you had any luck rebuilding your distributor??

Tom
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