I’m currently running a trio of Strombergs on the 312 dyno engine with all the idle circuits intact.  The choke plates have been removed from all the carbs at this point and air horns are being used.  The idle mixture control is extremely good and I have simply been setting all the idle mixture screws exactly the same on all three carbs.  Idle mixture control while working on any one of the six idle mixture screws is surprisingly sensitive.  I have oxygen sensors hooked up to the exhausts giving real time values and this makes it extremely easy to set the idle mixture.  Carbs are currently jetted 45’s on the ends and 48’s in the middle with the full throttle fuel mixtures being slightly on the lean side.  Being jetted with 52’s all the way around had the engine on the rich side.  When I receive the additional 48 jets from Aussie Bill, I’ll rerun the engine and verify that jetting is spot on before starting some serious 3X2 intake manifold testing.  I can acutally fine tune the final jetting to a small degree with the idle mixture screws at this point.

Bob.  Power valves are in all three carbs.  Vacuum advance on the distributor is not being used, only mechanical advance which has been fine tuned for this particular combination.  Lots of initial and then short and lazy up until a total of 38° is achieved.

And you’re right about the fuel pressure.  3½ psi fuel pressure is pushing it and have one carb that’s particularly finicky right there.  I’ll eventually change out the regulator that I’m currently using for the 3X2 testing as it’s a high flow regulator that just doesn’t like being backed down this low.  Already have some smaller sized regulators here so that will not be a problem when the time comes.