360 timing

360 timing

No ridicule or name calling. But again, "bleed off" is incorrect terminology. Overlap also does not lower cylinder pressure. It's dependent on when the intake valve closes. A later intake valve event will lessen cylinder pressure, because the cylinder starts to build pressure later in the compression stroke, conversely, an earlier intake valve closing event will raise cylinder pressure, all other things being equal. Most of the time, camshafts with a great amount of overlap also have a later intake valve closing event, but not always. It depends on the grind. But a later intake valve closing event will cause less cylinder pressure every time, all things being equal because it makes the cylinder build pressure later in the stroke. The cylinder simply starts filling later in the stroke, so less mixture is compressed. I didn't say you were wrong. You are essentially right. Just not right in the terminology, because all of this has to happen before TDC, not after.

funwithfuel said
Perhaps I stated what I was trying to convey incorrectly. Let me explain my statement, and I am by no meens trying to invite an argument on engineering, cam theory and all other things mechanical. I am just explaining what worked for me I built a lowly H-D sportster engine. Originally an 883cc . I converted it to 1200ish . I replaced the 3" cylinders and pistons for 3.560's . Now I didn't try to cram all that extra volume into the same tiny combustion chamber. I used heads with higher cc combustion chambers. It was still too much compression for the factory cams. I installed a set with greater overlap which "bleed off" some of the static compression Allowing me to step down from 105 to much more affordable pump premium 92 without retarding timing and without melting plugs and scoring cylinders. Keep in mind this is an air cooled engine that ran mufflers and sat in traffic quite often. I'm not totally "ignorant" to theory and application. And more often than not I do agree with you. Perhaps 9.08 :1 is a bit extreme. So..... what is factory compression for 5.9 magnum engine out of the box truck engine?.I await the ridicule and name calling..... Rant off.