"spec timing" for my mixed up e12 and vacuum retar

CBradio · Post by **CBradio** » Fri Jun 13, 2014 11:16 pm

I've touched upon this before:

I have a 77 530i, with its distributor too, but with a 528i cam.

I know the retard distributor will have more effect on timing than the cam, so I should start with 22 before TDC at 1700 rpm.

Maybe a stupid question, but if one had to guess, would the "spec timing" for my mixed up car be closer to the 22 before TDC at 2200 {for 528i}? I.e. would my timing be somewhere between 1700 and 2200 because of this cam? Say, 1850 ?

Also, does anyone know if its possible to swap out the vacuum retard on my distributor for the vacuum advance on the 528i distributor? If yes, even in theory, then my spec would be at 2200 rpm, right?

Does the vacuum retard causes some bog at idle? I know some would say just get the 528i ignition setup... thinking maybe

Mike W. · Post by **Mike W.** » Sat Jun 14, 2014 11:10 am

I don't think the cam would really affect the ignition timing, it's much more the distributor. If you have it set up right, the vacuum retard really isn't that bad, both 530 and 528 have considerable mechanical advance built into the distributor too. But even more than the curve is the fact that 528i's were electronic ignition, not the short lived points and condenser. And don't forget that the manuals say to disconnect vacuum control when timing it.

But I never really answered your question of where or what. I'd try it at stock specs first, then try to add a little advance and see how it runs.

CBradio · Post by **CBradio** » Mon Jun 23, 2014 1:18 pm

If I converted to the 528i's ignition system, with my cam, would my spec timing be at 2200 rpm then?

Side question: would I need those hotter 528i plugs, too?
Or is that a function of engine size?

{EDIT} To answer my own question, it seems it is not a function of engine size as the 633 uses the plugs with the 9 heat rating too..

CBradio · Post by **CBradio** » Mon Jun 23, 2014 10:27 pm

AND ONE MORE; slightly off topic. how advanced is too advanced?

I've read that some 528i owners will time to ~1600 rpm instead of 2200.

I timed my car "by feel" and then check with a light.
My car seems to be timed to about ~1250 RPM

Is this normal?

{EDIT} when I time to spec, my car runs hot.

I'm sorry guys I know y'all want me to get this thing running right