CFM = horse power / head flow

[gunmetal]

Can anyone tell me what a extra 50 cfm thru a set of heads translates to in horse power? Is there a formula that will show what happens when you add flow to a set of heads?  340 motor

Example:  stock 894 heads flow 221 intake at .50,  ported J heads flow 272 intake at .50.  What would that translate to in horse power?

[mrob]

It really depends on various factors, but an approximate formula is: 2.0 HP / cfm. So at 221 cfm, your motor could make 442 HP and at 272 cfm, it could make 544 HP.

Here's a link for an online calculator too: http://www.wallaceracing.com/calcafhp.php

[moper]

Like Rob said, if you are actually making good use of a set of heads, the estimate is 2hp/cfm. But, most engines don't make full use of a set of heads, and the milder the package, the less likely they will reach that level. Also, unless the same guy, used the same bench to test both sets of heads on the same day, odds are the numbers are not comparable. For instance, a set of factory heads that flow 272 at .500 would put up a red flag for me unless i know the shop that flowed them. That's a big flowing head and not easy to get in the real world.

[gunmetal]

Excellent information, I know nothing is written in stone with any numbers projected.

Thanks guys just what I was looking for.