[steve25]

Here are intake flow numbers tested on my bench from two different sets of 100% stock 6X-4 heads.

Out of all four heads , I flow tested 1 of the 8 ports that to my trained eye Looked the best and I also judge them for the least amount of core shift which would be another factor in the ports flowing the best.

On both ports that I tested I freshen up the valve job which sunk the valve maybe .003” and the flow test was done with a new stock nail head type intake valve.

Note, the OD of the factory valve job leaves a lot of added flow producing curtain area on the table!


The third column I post here is the maximum HP that could be made with a combo like yours.

This assumes 100% volumetric efficiency which is something that you with your combo will not achieve since you are pumping the exh out thru manifolds.

Due to this you should temper the HP numbers posted here by 10%, so yes motors built like yours would be doing well to make a 90% VE number.


I will calculate the HP number I post here from the highest flow number of these two ports tested.

Note that with a build like yours that once the motor reaches the rpm where peak torque is achieved that for the most part the intake port area that the heads have has been tapped out!

Flow @ 28”

Lift..........CFM....................HP

.100” 77.6.——78.3————-

.200” 134.9—-145.——-

.300” 179.9—-179.8——-

.400” 198.3—-203———417

.450” 202.4—206.5——-424

.500” 206.3—-208———-429

.550” 207.5—-211————-434

.600” 208.6—-213————438


If you where running a .500”lift cam then that 429 HP tempered by 10% drops down to 386 HP, and even that’s still being a tad generous with having under 10 to 1 compression!