Change late 230SL to vacuum advance

[lindi]

Hello together,

Im am new here in this forum. Sitting here in Germany, I am along with my 230SL for more than 30years. During I grew old, my SL stayed a beauty. A bit like in the film Highlander, but the other way round.

I always loved your forum because of the very sofisticated informations and discussions to be found.

An item, I am interested for years, is ignition and ignition curves and how things changed in our cars during the years of production. This, especially because of the results on the behaviour of our cars.

Coming from the early 230SL with a pretty sharp curve with vacuum advance, just like the W111 22SE, later changed into vaccum retard with the BOSCH distributors 051, in my eyes the character of thee engines changed from a lively one to a, perhaps, more calm one. Sure, there are other factors, too, but having changed our engine back from vacuum retard to vacuum advance and installed the older curve in our 123-ignition, i noticed a pretty increase of livelyness. Also the over the years existing problem of starting, when engine warm, suddenly was solved.

What I want to ask is, if anybody else has made such a change and what your experiences are.

Would be nice to hear from you.

Best regards
Lindi

[Montreal V8]

Hi Lindi.  I did the same thing on my US version of the 280SL, including the correct housing with the advance port. The first thing I noticed was a great improvement in warm starts. The engine does seem a nice bit livelier, plus it pulls better going uphill. So, installing a Getrag 5 speed, and enhancing the vacuum advance, made a nice improvement to the overall driving experience.
   Cheers,  Dale.
 

[yogich]

Hi Lindi,
on my 280Sl (US-Version) I did the same thing - went to a programable 123 Tune and shifted to the vacuum port and now it goes on vacuum advance only  - very nice improvement.
Engine starts perfekt warm and cold.

best regards from switzerland

Jürgen

[Naj ✝︎]

Hi, Lindi,

My '68 280SL is running on a 230 Vacuum Advance Throttle body and a contactless distributor (and blue coil and ballast resistors) from an M110 engine for about 10 years now. Very very pleased with the change in performance.

Also a little improvement in fuel consumption

naj

[lindi]

Hi together,

thanks for your messages.

Did all  of you use a new throttle body?

I used the original one, there is a hole at he right place, closed with a little allen bolt, exactly fitting for the small tubes to be used for vacuum.

Best regards
Lindi

[Montreal V8]

   Just checked my original throttle body, but it does not have an advance port, or an allen bolt. Perhaps the US versions did not have them.  I've heard of people drilling a required port, but the correct location is critical, so easy to make a mistake.
    Cheers,   Dale.

[Benz Dr.]

I see no reason to believe one system would work better than another. The early 230SL has a very quick advance curve which could give you a slight performance edge but that has little to do with one advance system over another.  That's all about advance curve from the flyweights and vacuum cell. On some distributors that can be adjusted to some degree and on others it's preset right from the factory.

I've been able to change advance curves and total advance on some units but it's not as much as you might imagine nor would you want to change certain parameters all that much or you could end up with pinging. I wouldn't go more than 5 degrees total between vacuum and mechanical.

[lindi]

Indeed there might be differences between US and European version.

For me it was quite helpful, because my desire was to have the early setup.

When I tested several curves, I found the early one, which is that one with a very quick advance, the best for a lively response. Having luck that our head has been surfaced only once, so that the height is still very good, we have no problems with the dangerous pinging.
I think the curve and especially the missing retarding at start, these two factors lead to that very good starting behaviour, I am happy with.

Thanks for your statements
Regards
Lindi

[rgafitanu@gmail.com]

Very interesting Lindi. I would like to do that to my 230 engine. I have the 51 distributor wit a throttle body with a small vacuum hole at the bottom right under the butterfly plate. Maybe I can see yours in July whe I will be picking up my AMG GT in Sindelfingen.

[Benz Dr.]

The 051 is a very good unit and when set up right it will perform nicely. Vacuum retard gives almost instant timing response because the advance plate is held at zero until you open the throttle. Mechanical advance works with RPM and that's where your total advance comes from. The 051 is set up with 10 degrees vacuum and 20 degrees mechanical. The mechanical portion is fixed but the vacuum portion can be adjusted.