RepairmanJack,

I don't know what viscosity Marvel Mystery Oil is but I think it is probably not 20 weight. I recommend 20/50 oil if you don't have and can't get straight 20 weight oil.

I am an SU novice. I loosened the bearing nut because I misunderstood it's function. I had to recenter the jets before I could adjust the carbs. Once I understood what all the pieces do (and got the jets recentered), it took me less than 20 minutes to adjust the carbs. The procedure is a compilation of instructions from Tom Bryant, the Haynes manual, and the Volvo green book for the B18.

Warm the engine.

Turn the engine off.

Remove the filters. Remove the choke cables. Back the idle speed set screws out.

Use the linkage adjustments to achieve immediate, simultaneous, and equal throttle initial openings (by eye). Turn the idle speed set screws in until the throttle plates just barely begin to move (again, equally).

DO NOT loosen the bearing nuts. Turn the jets fully up. Check that the needles and jets are centered. (Remove the damper rod. Lift the vacuum piston about 1/2 way up the bore and release it. It should fall with a definite solid sound against the floor of the carb body. If it doesn't make it all the way to the bottom of the travel, the jet has to be centered. Replace the damper rod. Check the other carb the same way.) If the jets are centered, continue. If not, no adjustment will make the carbs work properly.

Back off the jets 15 flats. Turn the idle speed set screws a half turn in to get started.

Start the engine.

Adjust the idle speed with the idle speed set screws equally to about 800 RPM.

Adjust the jets for fastest idle. Adjust first one then the other, back and forth, keeping the number of flats turned equal on each carb.

After you've achieved fastest idle, adjust the idle speed with the idle speed set screws equally.

Stop the engine. Install the choke cables and adjust the fast idle speed set screws until they just do NOT touch the fast idle cams. In other words, so that any movement of the choke cables cause the cams to contact the screws.

Install the filters.

Restart and rewarm the car. Ensure the choke and fast idle work properly. Ensure the choke is off before continuing.

At idle, push up on the rear carb plunger. If the idle increases, the FRONT carb is too rich. If it stumbles and/or dies, the FRONT carb is too lean. If it stays about the same the FRONT carb is correct. Adjust the FRONT jet as necessary. Push up on the plunger on the front carb to adjust the REAR jet as necessary.

Finally, adjust the idle speed with the idle speed set screws equally.

You're done; go enjoy the SU music. ;-)
--
Mr. Shannon DeWolfe -- (I've taken to using Mr. because my name tends to mislead folks on the WWW. I am a 51 year old fat man ;-) -- KD5QBL