Dwell setting point for different ignition point supplier?

[saygold]

I decided to change the ignition points on my SL as it has not been done for a long time.  I have a '66 230SL with a cast-iron 051 distributor.  I received  new two-part ignition points from Classic Mercedes; however, I was unable to install the points - I think the spring was too strong for an old man with stiff fingers.  Out of frustration, I ordered and installed a one-piece ignition point set (from NAPA if that makes any difference).  Both sets of points were designed for installation on a post.

The car is now running.  It ran fairly well with the dwell set at about 30; however, as I get the dwell setting closer to 38, the car is running worse.  If I set the dwell back to around 30, the car runs better with no other changes. I have installed a new distributor cap, rotor and cables.   

A comment in a previous post indicated that the dwell for one-piece ignition points being set at around 30; however, reference was made that the one-piece points did not use the post arrangement.  Unfortunately, I have not been able to find this post today for reference.

Does anybody have any experience on the best dwell set point for one-piece points or should I order another set from MB?

Thanks,

Ken
'66 230SL Euro, 4-speed

[Benz Dr.]

The dwell angle of a 051 distributor is around 38 degrees. Later aluminium distributors are set at 30 degrees. Is there any radial play on the cam lobe shaft? Radial play will make the points close up at higher RPM's as the point spring pressure pushes sideways against the cam lobe shaft. Increasing the dwell angle will compensate for this wear to some degree but a rebuild is the only way to fix this problem.

The point sets I use are two piece. Did you use distributor grease on the rubbing block?   

[saygold]

Thanks for your quick response.  I had added distributor grease before installing the points.  I had gone through the linkage tour and adjusted the rods as needed before starting the car.  After starting the car with the dwell set at around 30, I reduced the fuel addition during idling and increased the air flow to get a clean exhaust gas when running at normal temperature and at about 800 rpm.  Will increasing the dwell require resetting the fuel addition (and air addition) when the car is idling?

Thanks,
Ken

[Benz Dr.]

Much of this is basic stuff but it's still tricky to get it right.

 Idle speed consists of three basic elements: fuel, timing and air. Change any one of those and you will very likely change your idle speed. It's a matter of slowly closing in on that little triangle until you get the best quality idle that you can manage. Remember that ignition changes everything, so any adjustments to dwell angle will also change your timing, which in turn changes your idle speed. This info only sets your idle speed; ignition advance is another matter.

Check your ignition wires and make sure there are no carbon core wires. Coil wires are often carbon right out of the box. Save the boots and metal ends and get a proper piece of wire and make a new coil wire if you have this problem. I use NGK BP5ES spark plugs set at .032'' and 38 degrees at full advance at or above 3,000 RPM. Idle timing should be 8 degrees.

Check fuel pressure which needs to be at least 10 PSI. 14 PSI is better but often not found even on new fuel pumps. Check return volume after the fuel damper which should be 1 liter in 15 seconds. I would start with simply checking the cold start valve for function with a test light. If that's not working none of these other things will start your car.

[saygold]

I have the car running now - dwell at 38 and timing at 8 degree BLTC when idling.  Thanks for your comments and assistance.

Best regards,
Ken