cruising speed stumble/ hesitation

[al chamberlain]

my 72 monte with 39k original miles hates steady low rpm speeds. rebuilt the carb, full tune up to specs. started by eliminating tcs ( vac advance is working ) then started bumping up the timing ( which helped considerably ) . I'm at 12 degrees initial timing with no pings and about to go off the pointer. anybody experience this?? oh yeah, and here's the kicker, the leaner I adjust the carb, the better it runs!!! 

[Sam (Bones)]

what carb?

only adjustment you can make once the carb is assembled is the idle mixture screws, and if it runs better by closing them some, my first thought would be float level to high and pulling fuel from main metering while you are still running off the idle transfer slots

 

any off-idle stumble?

[al chamberlain]

2 barrel Rochester, and seems ok taking off from stop. the brass float I supplied through off my builder ( kit gave specs for plastic ). maybe we'll look into that. I'm at about 16 degrees and it's barely noticeable and still not pinging!!

[Sam (Bones)]

have you checked the mechanical advance in the distributor to make sure it's working?

and checked the vacuum advance to make sure it holds vacuum?

and make sure the dwell is correct? 1 degree of dwell = 2 degrees of timing

16 is a lot for a bone stock engine

[al chamberlain]

3 checks and yes, I know.