Another Vacuum problem, Maybe?

This is for a buddy's car. SBC 350. One day he was driving, the car died and we towed it back.

New fuel pump, carburetor, plugs and points ...

Dwell 26 - correct setting
Vacuum 16 in. - supposed to be 17 -21
Timing 14 -12 BTDC - was off gate
Plug Gap - .038

Can't turn dist any more to left, it stops. Ran out of room, to retard timing and bring vacuum in. up. Checked for vacuum leaks. Compression and leak down tests ... GOOD

It's like it skipped a tooth, but supposedly a double timing chain ??


Here are some specs on the car:

*Intake manifold: Edelbrock Performer.

*Carburator: Holley 780, dual feed, double pumper with vacuum secondaries.

*Compression ratio: about 9-1

*Fuel pump: Holley "mechanical pump feeds the engine & a "high volume" Holley "blue" electric pump feeds the
Nitrous system.
*note: the nitrous system has what is considered to be a "Stand Alone" fuel system!

*Heads: 194cc with Summit Racing 1.5 Roller Rockers.

*Timing Chain: Summit Racing "Double-Roller" timing chain.


*all billet aluminum pulleys.

*Griffin Radiator with 2 one inch cores to "super cool" the car. Its like having a 5-core radiator!!!

*Ignition system: A)MSD 6-AL box under pass side of dash feeding an Accel "super coil" under the hood.
Also has an MSD rev limiter, MSD shift lite, and an MSD timing box(to retard the timing automatically)
as soon as the nitrous button is depressed!

*Battery relocated to the trunk for better weight distribution

*sub-frame connectors

*traction bars(pre-loaded)

*mini-tubbed

*Pro-Built TH-400 Transmission with a 3500 stall converter

*B&M Quick-Silver "ratchet shifter".

*All Auto Meter gauges: fuel pressure, nitrous pressure, vacuum, oil pressure, water temp,
and 11,000 RPM "MONSTER TACH"

*Flow masters


Any thoughts would be appreciated.

Thanks

Try changing the coil, super coils have been known to crap out.

Sorry, after replacing the fuel pump, carb, and tune up from coil wire to plugs, she started.
The problem is it keeps backfiring out the carb under quick throttle. Easing on the throttle, she'll burn the rear tires off, or flat spot the front from pushing.

This is where when I tried to get timing back to 8-10 deg. BTDC and ran out of room after an 1/8 - 1/16 of an inch turn of the dizzy. Running at 12- 14 deg. now. Moving it that much also brought the vacuum up from 12 in to 16.


Thanks and sorry for not explaining things