[Cliff R]

I've seen blocks off as far as .027" from one bank to the other, and nearly that much in taper from front to rear.

I've also had 455 blocks in here fitted with TRW forged pistons (taller than stock pistons) that were almost EXACLTLY zero decked across both banks and needed nothing machined from them at all.

The rule of thumb for cutting heads and blocks is around .060". At or close to that point we start running into a situation where the intake will not sit down far enough to line up the bolt holes. You can elongate the holes or do one even better and have either the intake face of the heads cut, or the bottom of the intake.

It's also best to try to come up with a piston/rod length that puts the pistons no more than about .020" in the holes at TDC. This gives the machinist enough room to work with to get you to zero deck on both sides.

We consider decking/squaring and establishing tight quench MANDITORY for these engines at any power level. Your engine will reward you in several ways.

It will take LESS timing to make optimum power, and less octane to make that power. Most of these engines will also run cooler as they have improved combustion efficiency and naturally turn more of the heat into power rather than transmitting it to the jacket water.

The engine will also be more "balanced", as it's going to be closer in compression every cylinder assuming the combustion chambers are pretty close to the same size.

When it comes to this topic, and making optimum power with a street/strip engine on pump fuel, it's one of the places the engine builder needs to spend funds to end up with a better overall end result.

If you go after your new engine build doing this in every area, like good valve/seat work, effective head porting, cam selection/ putting it in the right place, full control of spark/fuel curves, etc, then you are going to enjoy that engine more than one that you grabbed up a set of 8 valve relief std bore pistons for, honed it with a rock, tossed in some rings, and put poorly chosen cam in it without degreeing and placed it in service......IMHO......Cliff