[cobra 53]

After several works and test drives I try to solve some carburator problems regarding the engine.

SPF 306
ALU Heads Ford J302
Intakes to heads portet
Comp Cam 288R @050 246/246. Dur. 288/288
Holly 600 vacuum
CR 10.5:1

Idling at 900 +/-:
Vacuum idling 7.0 - 7.5 hg
AFR idling 13+ / 14+.

Between these values the AFR leaps up to 20 and then back to 13/14.
Sometimes there are longer, sometimes shorter intervals between the leaps.

The engine sound on idle is like a hard working truck. Once it reaches the 1500/2000 RPMs, AFR is at 12+/13+ and vacuum +/-10, engine sounds very smooth.

Ignition timing is 12° at idling, 32° at 2700 RPM and 34° at 3000 RPM.

Is there probably a spark missing, which causes the leaps regarding the AFR figures?

Or what ...........?