[mikep]

I've run some pretty radical cams with vacuum secondaries as in up into the 305 advertised duration range with just a little tuning on the secondaries. AFB's arent my favorite carb for other reasons but the secondaries are certainly tuneable for low vacuum cams. I ran one on a 351 cleveland that wouldnt pull more than 10 inches of vacuum and the secondaries on it it ran just fine at WOT . All it takes is a little fine tuning of the secondary counterweight . They used them on 426 hemis for Gods sake and those things had minimal vacuum at at anything over idle . There a couple of good books on Carter tuning that go into detail on the subject. Theyre cheaper than rebuilding a holley and if you like the carter ( weber, edelbrock , carter...whatever ) otherwise you might as well run with it.