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.
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.
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.
