Everything, but seems mostly penis size. LOL.

When running simulations or performance trends dyno simulator a 4.0 stroke motor shows a internal friction loss of 270ish hp at 6500 where a 540 shows 320 ish due to higher piston speed, w identicsl heads, cam, etc the 540 has a tq advantage in mid range and the 502 shows a slight hp advstage above 6000, ie if the piston speed w 4.25 stroke ABOVE 6000 has a 35 hp advantage but 50 more hp of parasitic loss measured hp would be 15 less than the 502, ill take the extra power at 5000/5500 any day from the 540 though!

atmospheric conditions,

I have a camshaft design program. It seems to work very well against, what some cams/builds have seen on the dyno as far as powerband goes.

Anyone willing to guess, what change in .050 duration, there would be on a hyd roller, between a 502ci, and a 540ci, looking to make maximum power at 6000 engine speed, if all other things were equal?

Temperature, Humidity, Accessories and What number the builder needs to make, to meet customer expectations and agreement........lol.

Near 10* ? Maybe 12* ?

Baro, air temp, station press, humidity,altitude etc. To see 3% you need to have almost perfect air, ie low humidity and around 60 degrees intake air IF using j607, i cant see ypur dyno sheets on my ph but which cf was used, sae1349 yields numbers 3.9% lower than j607 . Crockett, mer, Eddie young, gellner etc all use j607, i use j607 on my dyno, a merc engine is dynoed at 1349 so if it makes 500 hp at merc and you put it on my dyno it should make 520 corrected. If your motor dynoed at 630 hp w 1349 if you put it on any dyno using j607 it would magically make 3.9% more, ie about 655hp, if it dynoed at j607 and you redynoed it somewhere using 1349 it would LOSE 25 hp and show 605hp, IF you were comparing it or ANY motor dynoed at j607 to merc hp numbers take 3.9% off to make comparison e+ual, only useful for comparing dyno to dyno though. 99% of shops use old j607 cf because their nbers would look low in comparison to other shops if they used 1349, fwiw, Smitty

^^^^Yes^^^

Here's the difference

SAE J607 standard of a 60°F day with 0% humidity and a barometric pressure of 29.92 in-Hg

SAE J1349 standard of 77°F day with 0% humidity and a barometric pressure of 29.234 in-Hg

I entered the parameters, for 5500RPM max. I don't want to hear the backlash from the 6000RPM durations, and how someone built a 632ci with a 224/234 cam and it rev'd to 7200.

454=229/234
502=233/240
540=243/252
572=252/263
598=253/266

7 to 10?