[minytrker]

Originally Posted by Pesce Nero

cylinder head flow determines what HP an engine is capable of making. when I say HP I dont mean rwhp numbers either.

the simple formula is 1.5 hp per cfm for a hot street engine
2.0 hp for your run of the mill cookie cutter race engine
2.2 for balls out, high comp, low tension ring, gas ported piston type deal

so a 40 cfm increase x 1.5 is a 60 hp gain. If you dont make that 60 hp gain then there is a reason like the cross section area of the intake is the restriction

that brings me to some more heads that I flowed today

I'll start with Texas Speed PRC 243 cnc heads with 2.0 valve

.1 72
.2 137
.3 199
.4 241
.5 284
.6 307

these heads have the rocker bolt hump and swirl hump removed, also the cross section of the port was wider than stock. if you bolted a stock intake and gasket to this head, it surely would limit its potential because the intake and stock gasket is smaller than the port


also brought over today was an AFR 225 cathedral port head with 2.08 valve

.1 75
.2 141
.3 203
.4 250
.5 290
.6 319

Also flowed today and I'm completely embarrassed about this because I ported these a few years ago, were 5.3 heads with 1.88 intake valve

.1 70
.2 134
.3 190
.4 216
.5 245
.6 253

Makes more sense, thanks. I was just asking because I dont know. I had one set of heads ported by Texas Speed and they cracked all the way through the runner. After that I have always been gun shy. I have also seen more "ported" intakes make less hp than before they were ported.
Do an increase in cfm always equal more hp?