Ignition distributor

[x2701]

Hi,

I have a question concerning the ignition distributor of my 1963 Volvo 122s 12234VF (Chassis number 112,800 till 139,999) with a B18D engine an two S.U. HS6. I noticed that the ignition distributor VJU 4 BL 33 has a vacuum regulator attached to it, with no hose connected. The Volvo service manual, PART 3 ELECTRICAL SYSTEM 120 (12 volts), says that the B 18 B and D do not have a vacuum regulator and in the next sentence the service manual says "the vacuum regulator on the B 18 A, D and B20..". I am a bit confused. I'd like to know which distributor is the correct one for my model and engine? Has the S.U. HS6 carburettor a low-pressure connector? According to my research, a number of different distributors were used for the B18 engine including the VJ 4 BL 34, VJU 4 BL 33, VJUR 4 BL33, JFU(R) 4, and the JF(R) 4 JC. Also, I'd like to know whether it is harmful to the engine to use a distributor that has a vacuum regulator with no hose attached to it.

Thank you so much,

Stefan

[Ron Kwas]

Stefan;

Short answer: If Carb(s) have a vacuum port that is left disconnected and open, this would be a point where False Air could be sucked in, which would not be good, but it is not harmful to Engine (or Distributor, or Carbs) if Vacuum Port is left disconnected at Dist, it just means that Timing curve is no longer influenced by Vacuum.

Long explanation: As you have seen, a number of configurations of Distributors in combination with Carb(s) exist for the B18/20...it looks like your Dist was changed at some point, to one with a vacuum input (Advance OR Retard, determine which by inspection! See: http://www.sw-em.com/Volvo%20Ignitio...e_Spark_Timing ) In short, Vac Advance helps performance a bit (on single carb configurations), Retard was added later for emissions and is a performance killer (besides making idle and performance inconsistent as the mechanism ages and becomes less and less repeatable).
I believe the dual SU configuration never used a vacuum influenced Dist, although the exact configuration was market dependent. If I was you, I'd check the (important) Centrifugal Advance was working freely (statically and dynamically with timing strobe, see info at link), and if you are happy with your road performance, I'd leave the Vac Port on Dist abandoned (plug it to keep out dirt), fine adjust Timing and Carbs based on roadtests and performance, but I wouldn't concern myself about this Dist Vac port much.

Gruesse aus Connecticut!