Do you have a boost timing retard box? to reduce the spark advance as the boost increases?
If not lock out eh advance curve and set the locked timing to 28 to 32deg BTDC.
If you have a boost retard box, lock out the timing and set the locked timing at 36deg BTDC.
Then set the retard box to retard the spark by 1deg per 1 psi boost. ( 8psi boost needs 8deg pretard) ( aprox.)
This is a initial base line tune up.
High boost will require boost referenceed power valves. If yours re not ,, keep the blower boost low
Blower drive speed ... 5psi max. Use the best gas you can. 92+++octane.
carb jetting 68 pri 78sec. Primary power valves 10.5"
Remove both carbs flip over and look at the pri and sec throttle opeing at idle.
preadjust all 8 barrels even so about .020 to .030" of the idle transfer slot is showing at idle.
reinstall. timing locked at 36deg for initial start up. Let the blower warm up. adjsut idle mix screws for best idle only once the blower is warmed up. Do not wack the throttle when cold.
start and hold rpm at 2500-3000 untill some heat getsin the blower case. set timing (Locked)
set idle mixture evenly 1000+/- idle speed.
spark plug gap .033" to .035"
start power testing at 26deg BTDC. ( either locked timing alone or 36deg - the boost retard (1deg/#boost)
start modest boost and work up on the tune. What is the engine compression ratio?
If 8.5:1 or higher do no go beyond 8psi boost on pump gas.
Watch the plugs for over heat/detonation/...