Somebody told me that recurving didn't require any knowledge or machine. Just put the springs in listed in this thread and it will be great.
Well, that sounds nice. Time to get the MSD springs and install.... and gather data. (Boo! Go away, facts.)
The chart shows test plots of 4 different springs in an FJ60 dissy.
The stock curve has a little too much advance in the critical 900-1200 RPM range, then hits the too sharp knee point to kill power at higher RPM.
A recurved desmog dissy has the advance pulled back at the torque peak, but then lets it fully unwind as redline approaches.
Then there's the MSD springs. They essentially lock out timing advance at any normal RPM resulting in a couple degrees of retard due to ignitor latency at high speeds.
TLDR: sticking the MSD springs in an FJ60 dissy is an engine killer.
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