Proper way to measure throat CSA

user-9274568 · Post by **user-9274568** » Sun Jun 19, 2005 10:16 pm

I'm sure it's been discussed, but I need a refresher course. Thanks Guys.

bill jones · Post by **bill jones** » Sun Jun 19, 2005 11:48 pm

-basically the throat is close to being round so radius squared times pi (3.1416) = square inch area.
-Radius is 1/2 the diameter.

user-9274568 · Post by **user-9274568** » Mon Jun 20, 2005 12:27 am

Any certain area below the seat, or just the smallest diameter? Also, subtract for valve stem

shawn · Post by **shawn** » Mon Jun 20, 2005 4:55 pm

Chad,
the area most people are talking about is at the "bottom" of the valve job. Depending on what angles are cut below the seat cut will dicatate how large this area is. For example if you have a straight 90* cut right of off the bottom of your seat angle your throat area would be very large percentage wise in relation to the valve diameter. If you have, for another example, a 60* cut off of that seat cut that will continue to shrink the throat diameter until you run out of metal.I hope you can visualize what i'm trying to explain.
Another thing, some of the best performing/flowing heads that i have seen don't have a "round" throat.They are also "biased" one direction.
shawn

Post by **ou812** » Tue Jun 21, 2005 9:23 pm

bill jones wrote:-basically the throat is close to being round so radius squared times pi (3.1416) = square inch area.
-Radius is 1/2 the diameter.

Isnt it cs x pi divided by 2?

bill jones · Post by **bill jones** » Tue Jun 21, 2005 10:54 pm

-what is cs?
-Show me an example of what your formula is all about.
-It almost looks like you are taking crossectional area and figuring out what the diamter would be.

Post by **ou812** » Wed Jun 22, 2005 1:14 am

cs = cross section. Say 1.8 throat diameter, so 1.800 x 3.1416 divided by 2 = cross section?

bill jones · Post by **bill jones** » Wed Jun 22, 2005 11:28 am

-doing this your way the answer is:
-1.8 x 3.1416 =5.655, divided by 2 = 2.827 square inches.
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-the way I have always understood it is:
-diameter divided by 2 equals the radius.
-radius squared times 3.1416 equals square inch area.
----------------------------
-1.8 divided by 2 = .9
-.9 squared (.9 x .9) = .81
-.81 times 3.1416 = 2.54469
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-This is what I've always thought was the square inch area and is also refered to as the crossectional area---same thing.

ADR · Post by **ADR** » Wed Jun 22, 2005 9:59 pm

diameter X pi = cicumference.....I don't think you want that.