Call Todd Marsh,, I showed here my 1/4 time increase from my 906 heads to bolt on heads from Marsh and went from 11.7 @ 114 mph to 11,4 at 119 ,,had to fatten the carb up some ,,and it pulled extra 4000+ RPM before the power fell off..used to die off about 5500 rpm now pulls hard thru 6K.
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