www.86garage.com

Pulse tuning (from opening of stack to the back of the valve head) using the induction wave or ram air formula:

720°-(Intake Open Duration or IOD)= Intake Closed Duration (ICD)

(target rpm) / 60 secs = rev per sec (rps)
rps X 360°/rev = degrees per sec (dps)
ICD / dps = time intake valve opens

Sound travels at ~1, 125ft/sec

example gratia (humor me ):

720° - 278° = 442° ICD

5000 / 60 = 83.33333333333333
83.33333333333333 x 360° = 30000 dps
442° / 30000dps = 0.0147333333333333 (seconds)

1,125' (speed of sound) x 0.0147333333333333 (secs) = 16.575' of travel length

16.575' / 2 = 8.2875' or 99.45"

I found that the ideal length would be 16.575" (notice how it's rather similar to the original footage in the above equation) of run length (again that's from stack opening to the back of the valve) for the induction pulse to arrive at the valve when it is open at the 6 "wave".

If the exhaust cam shares the same duration as the intake in the case then the ideal length for each runner to the end of the exhaust would be 16.575' (again from the exhaust opening to the back of the valve) and this would be at the first wave. 2nd wave is more realistic and would be 8.2875' or 99.45" full length.

I'm lazy & would use this:
http://www.bgsoflex.com/intakeln.html" onclick="window.open(this.href);return false;

Not as accurate, but will get you in the ball park.

Andrew

assassin10000 wrote:I'm lazy & would use this:
http://www.bgsoflex.com/intakeln.html" onclick="window.open(this.href);return false;

Not as accurate, but will get you in the ball park.

Andrew

Here's another:
Induction Wave Tuning Calculator