I used to stress the importance of the quench doctrine but in the past few years have diluted my conviction on this matter, especially in the area of most street cars. However, in all out race cars and high compression engines, yes, it is of the utmost importance.

From what I understand, most engine blocks are only out at the most by .015" from one corner to the other. If you take this number into consideration, you will be able to calculate the difference in c.r. to be less than .25 of a point. So if you are running a 9.5:1-10:1 compression motor and use 92-94 octane, it is easy to see that a quarter of a point of compression will not cause you grief. Add to this, if you have a large overlap cam, this reduces the compression even further. As for the difference of h.p. at the lower compression piston, depending on the overall h.p. rating, but it would only be a matter of 1-2 h.p. less per piston. So the hp loss is not a big issue and neither is pre-detonation.

On the other hand, if you build an engine to the tightest tolerances, where you might want to run 87 octane and have 9:1 compression, and if pre-detonation was to occur at 9.1:1, then yes, you should have the engine square decked.

Myself, I square deck and true bore all my motors. For the cost involved, it is a small price to pay. But if you are on a tight budget and you have room to play on the cr., then don’t bother.