Camshafts, idle quality, driveability and LSA-REAL WORLD EXP and OPINION

RAMM said

I totally agree. When I started this thread it was because I kept reading that LSA doesn't effect idle quality when I KNOW it does. LSA has a larger effect on idle quality than duration does. I also wanted to dispell the notion that cubes "eat" duration--totally false as well. When I decide on cam timing events I take into consideration so many aspects of the build from the hard parts to the totally subjective aspects it would take a long time to put pen to paper. I do have a bit of a "system" but its more based on experience and it wouldn't translate to paper well at all. J.Rob

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I have no evidenced to back it up from what understand that might explain why cube don't eat duration if flow ratios cfm per cid and intake and exhaust that a cam should act similar between different displacements as long as these ratios are similar. So for example if you take a 273 and 340 which have similar port flow to cid ratio it should take the same amount of time (duration) to fill the cylinders at a certain rpm say 6000 rpm for this example. But take 273 vs 318 since they both have same head a 318 will need more time (duration) at 6000 rpm or same cam will act smaller but if swap 340 heads on the 318 and compare it to a 340 the 318 will need less duration at 6000 rpm or the cam will act larger. I've seen evidence in a lot of the builds I've read but also sometimes theres ones that don't.