Intake Runner Length

[Van Setten, Tim (AZ75)]

> To my amazement the flow went up as compared to the vastly 
> unrealistic unshrouded situation I had before that. A quick 
> investigation with the 'flow direction and velocity indicator' (a piece 
> of sewing cotton tied to some welding wire), revealed that the flow 
> patterns had changed from being concentrated on the ceiling, to 
> being concentrated on the outside wall of the port, with the flow 
> curling around the valve stem . 
> 
> I found the optimum port shape changed significantly. A completely 
> different approach needed to be taken, than in my previous setup.
> 
> I had always heard and read about how ports set low in the head 
> don't flow worth a damn, but now I'm not so sure; my small low 
> rectangular exhaust ports almost outflow my high, round smooth 
> intakes! 
> 
> I also have a theory that low intake ports add significant swirl to the 
> incoming mixture, for very little cost in flow.
> 
> My 2c
> 
Exactly right!  We have been playing around with different porting schemes
and found that you don't want the air to tumble in around the valve,
instead, if you can make it swirl in (Vortec's idea?) you can get a lot more
in.  "Some" drag-racers claim that you want the swirl to go ccw also. (Why,
and for what purpose? I can't imagine).  We haven't got to playing with
square or rectangular runners yet.  Our cyl-to-bore ratio is 82%.  (It's
easier to turn up the boost to get more).
Good input, thanks.....Tim.