I agree. What is a good "rule of thumb" for HP/CFM for the average person? 2 even, or less?

 

marshall,

Do a search in Advanced Tech for "cfm per hp" and I think you'll find some interesting info.

I'd have to say that with everything "right" 2 to 2.1 cfm per hp is doable for a street build. Nothing written in stone... just based off of a great deal of data collection on my part.

-Mindgame

 

Yeah, I remember reading about it in there, I was just too lazy to search for it!


What do you think is the best 23º SBC head for a build like this. NON raised-runner.

 

Mindgame it was actually 2.20" the numbers were rounded off. Yours is up there anyways.

I agree with Mindgame on the DCR issue. I didn't really come across it till I was working on my first Engine Masters motor design in early 2002. Never had to push octane limits till then, so I had to find a way to figure out it's limits theoretically. That thing also made in the 2.0-2.1 range for hp per cfm. Going to the 7300rpm limit on it now and the bigger cam (LE2 range) will help it do that installed in the car.

I always liked Larry Meaux's thoughts on hp per cfm orhis flow factor.

HP / cylinder / cfm = flow factor

He also lists some ranges...

.22-.24 Good street car motors
.24-.26 Really Good Street, Decent Race Motors
.26-.27 Good Race Motors
.27-.28 Really Good Race Motors
.28-.29 Very Efficient Race Motors like Super Stock
.29 + Pro Stock Motors

It's not all about the port, but how efficent the motor is in making the power with the given amount of CFM it has. A .24 flow factor motor might still be pulling in the same amount of air as a .28 flow factor motor, but the more efficient motor has less losses so more power finds itself at the flywheel. Losses are found by increasing the thermal, frictional and airflow losses. There is more to a 258cfm port that makes 600hp than one might think. The more cfm you have the harder it is to make the motor as efficient. A 700hp 300cfm motor is not very easy to do!

Bret

 

Bret whats that formula above, im not getting anything that makes sense.

 

Ex)

600hp / 8 cyl / 290cfm = .2586 flow factor

Bret

 

thats what i was doing but wasnt sure on the decimal placement. Above you have everything listed x10.

Thanks

 

Brodix 15x cnc heads. Will keep making that kind of power from being cost-prohibitive, but you've got to jump to 15 degree hardware which isnt bad. More potential, better results.

 

Yeah it's right upstairs but sometimes the figers and eyes don't translate decimal points well....

Thank god cam duration is listed in whole numbers! In time we will probably be able to replicate them with .05 accuracy, then I'll be in trouble.

Bret