The published hp per cfm apply to the guy that published them, but might not apply elsewhere depending on details of the rest of the engine combination. I'll surely catch some flak, but 241 cfm @ 28" on SF-1020 made 625hp on a SF-901. Was with a 12.5-1, hyd.roller cam, 360ci, 10.20 @ 131 in a 3300 lb. car.

I keep my own notes on builds, and have my own expectations based on the entire combination.

Although the engine combo sounds light for that amount of power, you can't argue with actual et/mph. As long as the numbers are accurate.

Is this the same car w/ the 10.86 at 123 ET & MPH in the signature? What's it weigh, and under what conditions did it run that?

Even those seem subject to confusion (e.g. "flywheel hp" vs "rear wheel hp"), so they require qualifiers when used.

Unless the dyno results come from the one I've used the last couple of times (Porter Racing Heads'), I believe only what I can calculate from the MPH on an ET slip, at a measured as-run weight, under known atmospheric conditions that can be standardized for comparison. Everything else still throws in unknowns / variables that can skew the results.

it will be going in that car,that was with a 11.5 440,car weighs 3340 w driver.

FWIW:

My “really old” 440 combo (ported OEM heads, 254 at .050” SFT)
Best ET & MPH: 10.97@ 122.5
Weight: 3710 w/ driver
Formula HP: 532

My last 440 engine dyno results (ported Stage VI heads and 266 at .050” SFT): 610 HP / 570 Tq
Best ET & MPH: 10.52 @ 126.4
Weight: 3755 w/ driver
Formula HP: 592

Your ET & MPH: 10.86 @ 123
Weight: 3340 w/ driver
Formula HP: 485

My tracks are pretty close to sea level, and those times were from good-weather days. Adding close to a 1000 feet of track elevation, lower barometer, etc., and my 10.5s @ 126 would drop to 10.7-10.8s @ 122-123.

It is always possible to have combos that over achieve. The vast majority under achieve the 2 cfm per hp rule though. But really well sorted out combos with good heads, big cams and high compression can over achieve. My EZ heads flow 360 cfm and they've made over 900 hp on a short block with lot of compression, gas ported pistons, dry sump, etc. The 2 hp per cfm is just a rule of thumb that applies to the typical bracket type engine. SS, Comp Eliminator and Pro Stock engines get closer to 3 hp per cfm.

If the heads are small to moderately sized, with decent flow for their size, and are put on a motor big enough to easily "use them up", with enough compression and cam to do that, it's really pretty easy to beat the general 2hp/cfm(for a v8) "rule".

As an example, it's going to be a lot easier to make 650hp using a 300cfm edelbrock with it bolted on a 12:1 505 with a roller cam than a 10:1 383 with a flat tappet cam.

I see plenty of combos over on YB in the N/A forum where people are beating the "formula". Well.... That formula anyway.

My solid cammed 906 headed 12.1.1 470 made 615 hp and 580 tq.........

That combo and dyno results look right in line with what I would expect. I think a better intake/ carb combo would better utilize the 335cfm heads and make even more power.