Been having trouble with my '69 350 HO. It has a Rochester 4 bbl 4MV. The car starts and runs fine through the warm-up. When I get out onto the road it sometimes continues to drive well. However, other times when I pull up at traffic lights, (still in drive) it seems to lose RPM and feels/sounds like it starts to run rich. It gets that murky off beat kind of sound. If I leave it long enough, it stalls. It always starts again, but can take a bit of encouragement. If I give it a bit of gas before it stalls, it picks up again (albeit with a bit of effort) and when the lights change, off it goes again, driving nicely until the next lights. If I'm driving down hill with my foot off the gas it can feel like it's going to stall as well. If I just leave it in park after initial warm up it doesn't miss a beat. It's quite intermittent, though it does seem to be getting more consistently a problem.
I checked my carby. It had a new kit put through it about two years ago, and has only driven about 2000 miles since. The petrol is clean, 98 Octane and I do run a valve softener (but always have). The mixture seems ok, though I discovered that the the screws don't seem very sensitive for the amount of vacuum. Even so, with everything connected, it's pulling about 17HgVac (manifold) at about 750RPM running temperature idle.
I've read a whole bunch of stuff about it, but nothing's making sense, so I'm turning to the experts for help. Any help would be appreciated thanks.
