Calling all spark table gurus, wizards, and anyone with comments or suggestions.
I need some assistance in converting stock advance and retard values into a starting spark table. This is for a 2.5L straight 6 non-GM engine from the early 70’s. The only aluminum in the engine bay is the cable ties holding the hood release cable.
From the shop manual for the stock dizzy/engine:
Static timing: 12° BTDC (engine not running, crank turned by hand)
At Idle: 4° ATDC (800-850 rpm engine speed, no vacuum retard connected)
Centrifugal Advance:
Crankshaft RPM Degrees of crankshaft advance Minimum Maximum <400 No Advance to occur 1200 2 6 1800 8 12 2400 12 16 4400 21 25 5600 24 28
Vacuum retard
In. of mercury vacuum Degrees of crankshaft retard Minimum Maximum <1 No retard to occur 2 0 1 4 0 7 8 8 14 15 12 16
Engine/tranny mods:
1227747 ECM
Compression ratio increased from 7.75 : 1 to 10.5 : 1
Goodparts GP2 cam (specs at: http://www.goodparts.com/shop/index.php?categoryID=9)
Goodparts 1.65 : 1 roller rockers (stock 1.4 : 1)
Upgraded valve springs
Bored 0.040” over
Lightened flywheel ~21lbs down to 17lbs
5 spd Toyota transmission
Electric fan replacing mech fan
Run 92 octane fuel because of the higher compression and no knock sensor.
Car pulls well through 5500 rpm with the current table but I would like to start with something closer to stock and modify myself rather than blindly trust one of two considerably different provided with a mediocre tune via email in 2006.
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