Cool, now we will turn to some actual information.Kazoom wrote:
Thanks for providing that photo, because it illustrates the problem with the hi-port on a street car.
The only way to get a small flow gain is to have a port that is straight and exits very high, like in the cross section drawing in the middle. The problem is that the exhaust has to be in-line with the port to preserve the small flow gain, and that means the pipes have to go upward, turn above the rocker covers, turn down against the firewall, and then turn again to go under the car. STD flow 192cfm@0.0600" - HI-PORT 225cfm@0.600".
Now imagine std exh pipes that are perpendicular to the exh plate, and that exits down like a normal street car. The exhaust starts travelling upward, but now has to make a violent turn down because of the miss matched passage. PORTED exh without the hi-port 210cfm@0.600" - HI-PORT with perpendicular exit pipes 215cfm@0.600"
The 2 heads I tested with plates that had perpendicular exits built into the plate didn't flow as good as those hi-ports. 205cfm@0.600" and 215cfm@0.600"
I could do the hi-port heads because the chassis won't let you do the normal down turned pipes because the suspension and cross member is the way, and it it's actually a competition type vehicle anyway.
Make sure you can get your pipes in before you do a hi-port, because the flow will end up being equal to a straight porting if you can't, and that totally negates all the work.