[PHILLYGOAT]

I accidently picked up a Chevy mag at the supermarket(I promise I will never do it again!LOL) that had a head flow comparison. Some of the heads picked up quite a bit(from 2 to 15CFM I believe) of exhaust flow with an exhaust tube. When heads are flowed is there a "standard" of tube or no tube? How much difference would this make on a d-port head with a 167cc exhaust port that flows 185CFM @ .500" with no tube?

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Too stubborn to do it the easy way. What else would I spend all my $ and time on?

[PHILLYGOAT]

I accidently picked up a Chevy mag at the supermarket(I promise I will never do it again!LOL) that had a head flow comparison. Some of the heads picked up quite a bit(from 2 to 15CFM I believe) of exhaust flow with an exhaust tube. When heads are flowed is there a "standard" of tube or no tube? How much difference would this make on a d-port head with a 167cc exhaust port that flows 185CFM @ .500" with no tube?

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Too stubborn to do it the easy way. What else would I spend all my $ and time on?

[Dick Duclow]

If you contain the airflow, you increase the velocity. By using a length of tube you increase velocity, which raises the flow #'s

Most flow #'s are without the tube, but, the only way to know for sure is to ask the person reporting the #'s and hope they are telling the truth.