i have said this before in another post that people here didnt want to believe but if you have your block bore and honed with a torque plate you will see a big hp gain for doing this,and the other thing that might be better to do instead of milling your head down is to zero deck your block,mock up your new pistons in the bore and see how much they are in the hole, if they are .020 down mill the block .020,then you would have a zero deck block,much better for the burn, you can mill the head some too if need be.
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