How much power is it going to make???

[inkjunkie]

See this popping up frequently. And thanks to some very knowledgeable folks on this site often times, if not always, realistic numbers are given. A while back someone stated that something ot the effect of if the bottom/cam are picked for the amount of cfm the heads can move than doubling the cfm of the heads will get you in the ball park. Was digging around on anothe rforum a while back and found this


"Peak_HP = Flow_CFM * .257 * Number_of_Cylinders

This is the estimated potential Peak HP to expect.

You multiply 87 percent (.87) times cam's theoretical max lift , round off to nearest .050" in Flow Test, then see what CFM is at 28 inches of H2O.

example=> .700" Lift cam:
.700 Lift times .87 = .609" Lift
Flow head at .600" Lift , then take CFM at 28 inches and calculate HP potential with above formula.

.257 Factor = for beginning engine builders and engines near 10.0:1 Comp Ratio

.285 Factor = would be for Professional engine builders with wet sump pans, lightweight rotating assemblies, low tension great sealing rings, deep oil pans, etc. and excellent use of inertia/wave tuning with 9.5 to 11.5:1 Comp Ratios or 11.5 to 13.0:1 CR ranges without fully utilizing inertia/wave tuning effects

.300 to .310 Factor = Current ProStock Technology with dry sump, unlimited carburetion, High Comp Ratio, ultra lightweight rotating assembly, etc, and maximum use of inertia/wave tuning, etc, 14:1 to 17:1 Comp Ratios.

(usually no better than .3200 efficiency or no worse than .2980 eff %)"

Just wondering if this sounds reasonable?

Thanks....

 

[Bad Sport]

If you are an astrophysicist maybe.

 

[rumblefish360]

I stick with the layman's formula of max power potentail is CFM X 's 2.
It is basic, easy and accurate to a degree fine for bench racing and idle thought. Of course, a lot depends on how much advantage of the head and build combo. Since a pocket ported head at let's say 240 peak CFM flow math
Sticky works out to 480 HP. A lack of cam or other part of the engines combo will make a lot less. This also holds true in reverse for a larger than what would normally be used cam and sky high compression ratios.

Exceeding. Or failing to make the most of the head ow changes everything.

 

[OldmanRick]

I like Rumble's idea, nice & easy.

If i feel like playing with numbers, sometimes i use the wallace calc.
http://www.wallaceracing.com/calcafhp.php

As for accuracy.....?

 

[boosted]

damm that made my head hurt....

I say it will make enough to keep you happy for a short time before you want more..

At least that is how it works for me..