4k weber.
to the floor,is this straight off idle.
these carbys can deliver a lot of fuel.
is it fludding,were do the secondaries ,kick in
to early an the 4k just wont be able to suck it all down.
find where they kick in,then have a drive.
if it stops when ya hit the secondaries.
as above maybe blockage.
maybe that rich,it just floods to death.
it s easy to tweek where they kick in.
i normaly bring them on a little early.
but this sometimes creates back fires ,stalling,big massive flat spots ya got
keep ya revs up when ya take off.