Port Dimensions Quiz

[speedtalk]

What port cross sections do you watch?

I'll get it started, I focus on four:
1) Pushrod
2) Top of short turn (window)
3) Bowl
4) Seat Ring

[maxracesoftware]

I'll get it started, I focus on four:
1) Pushrod
2) Top of short turn (window)
3) Bowl
4) Seat Ring
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i "measure" all 4
and what i can't measure directly...i calculate what the velocity fps should be in that area .

the pushrod area choke is not as "Critical" as it used to be many years ago like on 292 turbo heads and such designs

with modern Chevy SB2, Canted Valves, etc (Jesel offest rockers/lifters)
has taken a bunch of choke off in this location

[rmbuilder]

i "measure" all 4
and what i can't measure directly...i calculate what the velocity fps should be in that area .

Larry,
Once you calculate the velocity how do you read and alter the actual numbers to obtain the desired fps? What % of 3 to 4 to you target?
Bob

[maxracesoftware]

What % of 3 to 4 to you target?
Bob

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all of it, the entire tract, everywhere is important


and i try to enlarge port in highest velocity region if velocity is too high

and vice/versa ... use epoxy in dead areas of port

[bsfc9]

the first dimension i look at would be the seat ring and next i would be most concerned with the window area, the bowl area seems to follow then i will look at the p.r. choke(on most ports). i like to make port molds--makes difficult areas of the port more accessible to measurement.

[SW]

I think that for most of us, there are usually limitations on what we can and can't do with a head depending on the classes that they are run in, rpm limitations,and buget. I have some "cheats" that i use to get me in the area that i need for min. cross section, based on the application. From there i would look at valve diameter needed for the application. or what you can stick in there,lol.After that i work my way back to the port opening. Sometimes this is an issue, like Larry had stated, with older heads or cast heads required by some classes.I hate it when you get to the point where that pushrod area is the min. cross and you can't do anything about it because of rules.The difference in velocity between the min. cross and the throat, in an open type head, usually is around 3%-5%.Again this will change depending upon application.
Shawn