popping: carburetion? ignition? or?

i was hoping i could get someone to help me troubleshoot the following.

400 small block up to 4500 rpm, 4150 mechanical double pumper with stock
out of the box setup, stock distributor with new hei in-cap and rotor,
solid copper core wires, accel shorty plugs non-resistor.

i would take the nova out for a drive, and the engine fully warmed up.
normally i drive with the lightest foot... and everything's fine. but
under hard acceleration, opening up the carb to WOT, i would
occasionally experience what sounds like a tight metal cable snapping
loudly, what feels like the engine stopping for a moment, and then
continuing normally.

i thought i was lean for a while... i checked the plugs and they seem to
read fine; i compared them against a chart of what good, healthy plugs
should look like vs. warning sign plugs. i've tried solving this problem
in the past by running a larger secondary nozzle, but no dice. i stepped
up the secondary jets 1 size up.. but still no dice, and the plugs
started showing signs of richness.

afterwards, i thought it was because i was running 87 octane. however, i
remembered this happening as well even when i ran 93 regularly.

i'm thinking it might be ignition, but i don't have any experience with
ignition systems, and i don't have the troubleshooting experience to
know where else to look other than what's above.

do you guys have any suggestions what i should be looking for/trying
next? opinions?

Gerard wrote:
>
> do you guys have any suggestions what i should be looking for/trying
> next? opinions?

Check the ignition advance unit. If it's a vacuum advance, replace the hose
and see if that fixes it.

George Patterson
A man who carries a cat by the tail learns something that cannot
be learned any other way. Samuel Clemens

"G.R. Patterson III" > wrote in message >...
> Gerard wrote:
> >
> > do you guys have any suggestions what i should be looking for/trying
> > next? opinions?
>
> Check the ignition advance unit. If it's a vacuum advance, replace the hose
> and see if that fixes it.
>
> George Patterson
> A man who carries a cat by the tail learns something that cannot
> be learned any other way. Samuel Clemens


It's a worn cam lobe. The small-block Chevies had a real problem
with that. The exhaust valve doesn't open much, and the pressure in
the cylinder blows back into the intake manifold when the intake opens
and burns the incoming charge, making a pop in the carb.
Seen it several times.

Dan

now there's something i didn't consider... interesting. i'd believe it,
too, because i think my cam and lifters are on their way out.
>
> It's a worn cam lobe. The small-block Chevies had a real problem
> with that. The exhaust valve doesn't open much, and the pressure in
> the cylinder blows back into the intake manifold when the intake opens
> and burns the incoming charge, making a pop in the carb.
> Seen it several times.
>
> Dan