advance or retard distributor

[georgem]

Could someone help me identify whether the distributor in my car (230SL) is one or the other. The vacuum take off from the manifold is at the top of the manifold (for a vacuum advance distributor) however I have my suspicions that its an vacuum retard distributor. Other than the serial no, what is the difference in appearance between the two?

Any help would be gratefully received.

George
Brisbane
230 SL

[ja17]

Hello George,

The vacuum units point in different directions on the distributor depending on which one you have. The vacuum retard points in the clockwise direction and the vacuum advance units point in the counterclockwise direction.

Joe Alexander
Blacklick, Ohio

[Naj ✝︎]

Hello, Gearge,

Also have a look at the wiki may help:

http://www.sl113.org/wiki/pmwiki.php?n=Electrical.Distributor

naj

68 280SL

[georgem]

Thanks Joe and Naj,

Naj, reading the WIKI piece is what started my train of thought re the mismatch - its a great site.

Joe, thanks for the tip re identification - you confirmed my suspicion; advance manifold, retard distributor. SO, which way to go, do I tap into the bottom of the manifold on the other side of the butterfly for vacuum, or search for an advance distributor. Are there pros and conns of each? If I look for another retard dist, can it be any dist as long as its a retard or must it be the specific one?

Cheers

George
Brisbane
230SL

[ja17]

Hello George,

The vacuum retard distributors are designed to use max vacuum at idle with the venturi closed.  The vacuum advance distributors are designed to use little or no vacuum at idle. Check the vacuum at idle to identify the correct port. Use the distributor for the vacuum supplied. The SL distributors have advance curves which are unique, so try  to use one of the distributor numbers correct for the SL engines. See Naj's list for the correct numbers. You may want to use the timing specs for the specific  particular distributor you have,  if it is not the original.

Joe Alexander
Blacklick, Ohio

[georgem]

Joe and Naj,

Thank you both for your help.

In the end, I think I will try and round up an advance dist. - drilling a hole for the vacuum off take in the bottom of the manifold isn`t a major job - but it does drift the car away from originality.

Now, does anybody know of a serviceable advance distributor............ ebay here I come.

Thanks again

George McDonald
230SL
Brisbane

[Naj ✝︎]

quote:Originally posted by georgem

Joe and Naj,

Thank you both for your help.

In the end, I think I will try and round up an advance dist. - drilling a hole for the vacuum off take in the bottom of the manifold isn`t a major job - but it does drift the car away from originality.

Now, does anybody know of a serviceable advance distributor............ ebay here I come.

Thanks again

George McDonald
230SL
Brisbane

Good choice George,

IMHO. :?

I would say that my 230 with the advance distributor ran much smoother and sweeter than my 280 with vacuum retard does. There may be other reasons too but sticking with advance would be my choice.

Good luck

naj

68 280SL

p.s: contact me off line. I may be able to get an 046!

[Benz Dr.]

The 046 is for the early engines on 230SL and is hard to find. It's also the most difficult to set up and make work properly because it has a very sharp advance curve. I think total advance on that unit is about 40 degrees @ 3,000 RPM. It takes a distributor testing machine and a lot of fiddling to get that particular unit to work right and it might be the most difficult build that I do.

Dan Caron's
 SL Barn
benzbarn@ebtech.net
 slbarn.mbz.org
  1 877 661 6061

[J. Huber]

quote:Originally posted by Benz Dr.

 ...I think total advance on that unit [046] is about 40 degrees @ 3,000 RPM. It takes a distributor testing machine and a lot of fiddling to get that particular unit to work right...
Dan Caron's
 SL Barn
benzbarn@ebtech.net
 slbarn.mbz.org
  1 877 661 6061

Hey Dan, can you elaborate on the 40 at 3K thing. I have mine at 30 -- should I adjust out.

James
63 230SL

[Naj ✝︎]

quote:Originally posted by J. Huber

quote:Originally posted by Benz Dr.

 ...I think total advance on that unit [046] is about 40 degrees @ 3,000 RPM. It takes a distributor testing machine and a lot of fiddling to get that particular unit to work right...
Dan Caron's
 SL Barn
benzbarn@ebtech.net
 slbarn.mbz.org
  1 877 661 6061

Hey Dan, can you elaborate on the 40 at 3K thing. I have mine at 30 -- should I adjust out.

James
63 230SL

James,

On top of the 30 degrees centrifugal advance you set your engine (@3000 rpm), you get an additional 14 +/- 3 vacuum advance @ 4500 rpm under load conditions. See distributor settings table in the 'wiki'.
You cannot check this in your garage, but if your vacuum advance is working correctly, you will get it when driving (i.e. under load conditions) I believe.

naj

68 280SL

[J. Huber]

Ah. I see, Naj. Thanks. I'm guessing mine is fine then. Anytime I am at 4500, things seem to purr along fine...

James
63 230SL

[georgem]

From Joe and Naj I now understand the difference between the advance and retard distributors and how they work, but it begs the question WHY - why did Merc change from the traditional advance distributor to a retarding one. Does anyone have any idea why they changed and maybe at the same time advise the advantage of one type over the other.
Note. Up until now I have owned a string of British marques, MGA, MGTF, XK150 Jag and currently an Austin Healey 3000. To be honest I have never heard of a vacuum retard distributor. There MUST be a reason why they began using one.

As an aside, the Healey 3000 is parked alongside our 230SL in the garage. They are both of the early 60s. When I open the bonnet of each and compare,(both are fully restored and in excellent condition), one looks like a billy cart built in someones back yard, the other looks like a highly sophisticated engineering masterpiece. Guess which is which!

Cheers

George McDonald
230 SL
Brisbane

[glennard]

georgem, As said before, don't think MB built two cars (engine management, etc) alike-different distributors, FI pumps, fuel pumps, start relays, start solenoids, etc., etc.  Celebrate your individuality!!!

[Benz Dr.]

Let me shed some light on this:

If you have the early vacuum advance unit with the wrong throttle valve you will only get mechanical advance. You need the vacuum to get the extra 10 degrees of timing on a 046.

The reason for vacuum retard is simple. It works. You have close to maximum vacuum at idle and this easily pulls the advance plate inside the distributor to the zero position. As soon as you start to throttle up the vacuum will begin to drop and the spring inside of the vacuum cell will force the plate to move in the direction of advance. Even if the system has small leaks it will still work in most cases. The same can't be said for vacuum advance. All the later systems use vacuum retard including the v8 engines.

Dan Caron's
 SL Barn
benzbarn@ebtech.net
 slbarn.mbz.org
  1 877 661 6061

[230slhouston]

George,
I seem to have the opposite situation. Are you still looking or willing to trade an advance for a retard dist?

I am waiting for more replys to my post before finally deciding.

Why would someone mix up distributors?

Thanks
MB.