Author Topic: 230SL Timing  (Read 5889 times)

Mercedespartsjeff

  • Guest
230SL Timing
« on: June 23, 2011, 17:44:48 »
Hi All,

I have a quick timing question:

65 230SL 046 vac advance distributor. Should it be 30 deg btdc at 3000 rpm with or without the vac line hooked up?

If I time it without the line hooked up, I get about 4 btdc at idle. If I time it WITH the line hooked up I go about 8 atdc.

Thanks,

jeff

Benz Dr.

  • Vendor
  • Platinum
  • ******
  • Canada, ON, Port Lambton
  • Posts: 7219
  • Benz Dr.
Re: 230SL Timing
« Reply #1 on: June 24, 2011, 04:58:55 »
This would indicate that you have a vacuum signal going to your distributor at idle speed which you shouldn't have at all.

There could be one of several problems:
 a ) idle speed set too high causing the mechanical portion inside of your distributor to advance slightly.
b ) throttle plate not fully closed allowing a slight vacuum signal to your distributor
c ) throttle plate is fully closed but vaccum port inside of the throttle housing is open to manifold pressure.
d ) distributor is worn out and needs rebuilding
e ) all of the above

The throttle plate should be in front of the vaccum port on VA systems at idle and only when the throttle valve is opened should a signal to the distributor develop. I've had to carefully file a small amount off the leading or trailing edge of the throttle plate to affect a vacuum signal depending on the system used.   
1966 230SL 5 speed, LSD, header pipes, 300SE distributor, ported, polished and balanced, AKA  ''The Red Rocket ''
Dan Caron's SL Barn

1970  3.5 Coupe
1961  190SL
1985   300CD  Turbo Coupe
1981  300SD
2013  GMC  Sierra
1965  230SL
1967 250SL
1970 280SL
1988 560SEC

Mercedespartsjeff

  • Guest
Re: 230SL Timing
« Reply #2 on: June 24, 2011, 17:02:15 »
Hi Benz Dr,
Thanks for the reply. I will check the idle speed and make sure the throttle plate is fully closed. I just had the distributor checked and cleaned up by one of my customers who is a component restorer so I'm pretty sure the distributor is ok.

I also get around 40 degrees btdc with the line hooked up if idle is set at 4 btdc and 30 degrees btdc without the line hooked up and idle set at 4 btdc.

So which is it? Should the total timing be set with the vac line hooked up or disconnected? I saw a thread on a 280SL that said the line should not be hooked up, but thats a completely different distributor number.

Thanks!!

Jeff

J. Huber

  • Full Member
  • Platinum
  • ******
  • USA, CA, Cedar Ridge
  • Posts: 3061
Re: 230SL Timing
« Reply #3 on: June 24, 2011, 17:27:35 »
I set the timing with the vacuum line not hooked up.
James
63 230SL

Benz Dr.

  • Vendor
  • Platinum
  • ******
  • Canada, ON, Port Lambton
  • Posts: 7219
  • Benz Dr.
Re: 230SL Timing
« Reply #4 on: June 24, 2011, 17:50:51 »
I don't know where the idea to disconnect the vacuum line came from but it's not the way I would do it. The engine runs with verything hooked up, right?

 The vacuum advance distributors run with more total advance which is why the 230SL produces as much power as it does.
1966 230SL 5 speed, LSD, header pipes, 300SE distributor, ported, polished and balanced, AKA  ''The Red Rocket ''
Dan Caron's SL Barn

1970  3.5 Coupe
1961  190SL
1985   300CD  Turbo Coupe
1981  300SD
2013  GMC  Sierra
1965  230SL
1967 250SL
1970 280SL
1988 560SEC

Mercedespartsjeff

  • Guest
Re: 230SL Timing
« Reply #5 on: June 24, 2011, 18:00:59 »
Hi All,
Thanks so much for the input.
So Dr Benz, should the timing be set at 3000 rpm 30 degrees btdc or is 40 acceptable for the 046 distributor? 1965 230SL.

Thanks,

Jeff

jacovdw

  • Guest
Re: 230SL Timing
« Reply #6 on: June 25, 2011, 09:09:45 »
I don't know where the idea to disconnect the vacuum line came from...

That is mentioned in the Service Manual (or BBB) group 00-0, where there is a table published with various values.

The purpose of the table is to provide test values to evaluate the performance of the distributor to see whether it is operating within specification.

The test values are as follows (assuming an engine at operating temperature and Bosch 046 distributor):

800 rpm (with or without vacuum): 8°
1500 rpm (without vacuum): 13° - 20°
3000 rpm (without vacuum): 30°
4500 rpm (without vacuum): 30°

4500 rpm (with vacuum): 30° + 11° (-3° or +3°)

That is why it is generally accepted that the timing should be adjusted to 30° at 3000 rpm with the vacuum hose disconnected.


Benz Dr.

  • Vendor
  • Platinum
  • ******
  • Canada, ON, Port Lambton
  • Posts: 7219
  • Benz Dr.
Re: 230SL Timing
« Reply #7 on: June 26, 2011, 06:33:46 »
OK, well the book is telling you one thing and I'm telling you something else but it's still the same thing in the end. Since I have a distributor tester I do all of those tests on the machine and not on the car. Believe me, the tester is FAR more accurate.  8)

I look for total mechanical advance and total vacuum advance while doing my tests. The mechanical advance is a preset amount and can't really be changed so the total advance is set using adjustments on the vacuum cell pull rod.

 The BBB is a guide only. Some of the stuff in there is complete nonsense ( as far as MB goes ::) ) and some of it is cast in stone. If I were to simply check the timing on an early 230SL with a timing light, I'd look for total advance and timing at idle with the vacuum line connected because that's how the engine runs. At the very least you want 30 degrees at 3,000 RPM ( which any working unit will do ) or the engine won't perform very well. :P

 It would appear that what I said was right and that the early distributors run at a higher advance than the later 051 units which are set at 30 degrees total. I know this because I've rebuilt enough of them to know how they work. The BBB tells you what they're supposed to do but not how they do it.

So yes, 40 degrees is possible with the early VA unit.  The early unit is VERY hard to set up. The advance curve is almost a vertical line and is very fast. Most of the later units will only give you 10 degrees of advance at 2,000 RPM. The early unit will give you close to 20 degrees by 1,500 RPM and the full 30 degrees by 2,500 RPM. The extra 10 - 12 degrees is set by the vaccum advance but that comes in much sooner than the mechanical advance and is probably all done by as little as 1,500 RPM.

 Try figuring out how to set up this mess using only your engine and get back to me. ;) I've spent hours trying to get one '' just right '' with my machine. You can't do it on the car.
1966 230SL 5 speed, LSD, header pipes, 300SE distributor, ported, polished and balanced, AKA  ''The Red Rocket ''
Dan Caron's SL Barn

1970  3.5 Coupe
1961  190SL
1985   300CD  Turbo Coupe
1981  300SD
2013  GMC  Sierra
1965  230SL
1967 250SL
1970 280SL
1988 560SEC

jacovdw

  • Guest
Re: 230SL Timing
« Reply #8 on: June 27, 2011, 14:22:04 »
Dan,

I agree that the distributor tester is the most accurate way of setting the distributor off the car.
Unfortunately some of us don't have or have access to a distributor tester and therefore the values in the tables published in the BBB is just that, a guide to see if your distributor is operating within specification.

I think that it would be a safe bet that most distributors would benefit from a refurb (if necessary) or cleanup and calibration on a tester especially if said car has been neglected or in storage for a number of years. After all, some owners are still running with original (40 years +) distributors.

Benz Dr.

  • Vendor
  • Platinum
  • ******
  • Canada, ON, Port Lambton
  • Posts: 7219
  • Benz Dr.
Re: 230SL Timing
« Reply #9 on: June 27, 2011, 15:18:16 »
True.
I see all sorts of things but most common are worn bushings, broken or worn springs, and seized advance mechanisms. Once in a while I'll see worn advance plates and I just did one where the actual cam lobe shaft was bent. No idea how that could happen because that metal is very hard - can't be touched with a file. Could have been a manufacturing defect.
1966 230SL 5 speed, LSD, header pipes, 300SE distributor, ported, polished and balanced, AKA  ''The Red Rocket ''
Dan Caron's SL Barn

1970  3.5 Coupe
1961  190SL
1985   300CD  Turbo Coupe
1981  300SD
2013  GMC  Sierra
1965  230SL
1967 250SL
1970 280SL
1988 560SEC

Mercedespartsjeff

  • Guest
Re: 230SL Timing
« Reply #10 on: June 27, 2011, 15:40:05 »
Hi All,

Thanks again for all of the specific information on my distributor. Apparently it is working perfectly! I was just worried that too much advance (40 - I thought with vac line connected at 3k rpm) btdc would result in preignition. I am grateful for the peace of mind.
Also replaced the plugs with the NGK's and that made a world of difference too.

Thanks again,

Jeff