And what primary pv? Need it be high flow?without being there to see how it acts can't say for sure but go up 1 step at a time. put the out of the box squirter in. and slow down the secondary. you timing sounds decent where it is.
If I just do what you wrote, I'll be back to backfiring when quickly opening the primary throttle. I was assuming somehow a different PV was going to help that?
I got hung up working/cleaning the catastrophe of a shop yesterday and never got to recheck the secondaries for any blockages. I had put air through the metering block again when it was apart again, but didn't double check the carb body.
I don't know about the choke. It seems to start fine without a pump and with the choke open 1/2", but the fast idle cam is on the lowest fast idle and it stalls in gear. Maybe I'll try wiring the choke open and turning the adjustment richer so I get a higher fast idle? Just to test it anyway. (I'm into experimenting, I know, you hate that) Why is it that it starts with no pump or much of a choke? I had a similar problem with a Q-jet and since it was old and I really didn't care about it much, I drilled and cut two large slots in the choke so it could breath a little while on fast idle. But this carb is fairly virgin so I hate to do that to it. It is not too much fuel pressure leaking into the intake. It just simply starts in less that 1 revolution with the choke probably not doing much at all at cranking speed and 1/2" open.