😅I build lots of different engines from busas to Harley’s to LS and besides diagnosing general engine health, I may use cranking compression just as a gauge so to say. Just like with my dyno it’s a tool for making comparisons and gleaming any little info I can cause just like you said, these engines don’t have brains and don’t talk so whatever data I can extract I can turn into possible useful info/knowledge to help in the next build. As any engine builder should know, cranking compression is mostly just a function of intake valve closing position. The sooner you close it (smaller numerically) the sooner it start building cyl pressure and vice versa. One of the hardest concepts in engine design/building for high power is the dynamic relationships between all the camshaft variables we are able to build into a camshaft-ie. Lift, duration, valve timing events, separation angle, etc etc and how they each individually and combined work together with foremost planned useage of engine and the particulars of said engine such as bore stroke static compression, etc etc. if an engine builder can TRULY get a strong handle on the complex relationship of camshaft design to engine specs and resulting output then rest is relatively easy. Now certainly one must understand it all including cylinder head airflow and fueling and induction as well as exhaust systems but beyond the basic function camshafts are the most misunderstood aspect of engine building for performance. You sum it up reeatedly all the time george and I wonder how many people it just goes in one ear and out the other. When you say, you just put the biggest bore, the biggest valves (starting at intake with exhaust an afterthought to the intake), cut the ports to match those valves and that’s basically the key. That’s a truly profound statement that I’m betting many don’t see as the true gem of your teachings. If you do that then you’ve optimized the basic engine geometry for maximum peak hp, then a cam choice becomes simple if you know those things plus a little cylinder head data and your there. The least restrictive exhaust that still provides scavenging (2 into 1) for NA builds. Your there. Induction and fueling is an afterthought in the goal is to not restrict/choke the inlet path you just built into the head. Fuel injected Harleys are not very sensitive to intake manifolds selection so long as you are not limiting mass flow due to too small of cross sectional areas. Easy enough verified with $30 set of internal snap gauges and/or flowbench confirmation (don’t care about particular cfm # so long as it doesn’t restrict what the head does by itself. I built a mild 124 twin cam made 140hp with 58mm tb. Air fuel set and plenty injector headroom. Bought the big HPI 68 and didn’t gain a single horsepower or lb ft of torque anywhere. Ran exactly the same up top down low everywhere. These aren’t carbs that need a signal across an emulsion tube/main jet. People get hung up in the wrong places and with antiquated carbeurated engine tech too often. Injector sizing itself is just a mathematical formula for supporting maximum possible output of engine with some headroom (stay at 85% duty cycle)
CCP is useful when choosing cams for Evo/ some twin cams which don’t have compression releases. If the m8 didn’t have them, the 220-240lbs ccp would be needed to know because starting issues I’d suppose.
