I'm not sure if each port is tested - on a blueprinted motor I'd be surprised if they don't flow every port - and then match them.
Numbers I've usually seen are run at 28 in. of H2O - a measure of how hard they're pulled on (sometimes 25 in of H2O) - and you'll see a scfm measure for every tenth of an inch of valve lift from .100" up to the most lift that head would likely see - usually .600" or .700". More and more cam designers see the importance of flow characteristics at low levels of lift, and I've had them ask me for flow numbers at .025", .050",.075", .100", .150", .200" and then in tenth increments up to .6 or .7. Hope that's helpful - M
Typically one port on each head is tested. But there is no industry standard. If a shop wants to test all the ports and pick the best, they can. With the advent of CNC porting, the ports should all be the same. Professionally hand ported heads should ideally be identical, as well. Variation means less power...
I know this is a little off subject, but do you guys think that taking a cartridge roll to my TW heads would help the power/velocity any? Since it's not really removing any material do you think this would only be beneficial? What about the combustion chambers as well?
The one place I would use the cartridge rolls would be in the chambers around the valves. TFS cuts around each valve seat to help w/ low lift flow. This cut works but leaves a sharp ridge. I would carefully smooth out this ridge and any other left over casting marks you might find. If you hit a seat, you will need to get a new valve job.
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