71 340 Compression Test

OK on all above. And agreed that you can target a range of DCR's. The lower numbers are what I consider very safe numbers, and practically anyone can put an engine together and run garbage fuel in it, never tune it up, and never have an issues. But being too conservative seems to me to throw away a significant benefit for a street engine: low RPM torque.

The extra HP is indeed small but that is not what we are after with higher CR and not what is of value on the street; it is the low RPM torque and the widening of the lower end of the torque band. If this benefit did not come with added CR, then we would all run 6:1 SCR and never worry over detonation!

And FWIW, the engine I mentioned would ping on regular and so I knew I was running it as high in CR as I could on the street with that setup and my tuning abilities. It ran a cam with 254/264 advertised duration which most people would tell you would be a detonation problem with 10.3:1 SCR. But I always credited the quench with buying me some good margin against detonation. And straight up cam timing.