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Old 01-31-2009, 09:22 AM   #1
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Join Date: Dec 2006
Fan#: 41846
Location: Calgary, Canada
What I Drive: 2001 Red ZTS

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Head flow vs. tq/hp

Tom, looking through the Focus Builder's handbook.....

seems to me, through all I've ever read, that making hp/tq throughout the band, and particularly down low, that a full ported head is not always the best thing. It appears that you get nice HP increases in the top of the powerband, but only after it starts falling off at 5800 or so. And sacrifice low end torque.

It also appears that you get more significant flow gains on the exhaust side with some porting, but the intake side deosn't post up the same increases.

So, if you would please take a moment, I would respect your clarification on a couple of things:

1) do the intake and exhaust flow numbers need to roughly correlate? If you have the ability to dispell the exhaust gases faster is it a useless endevour if the intake flow and combustion doesn't produce enough to take advantage of this?

2) with your FI work through the years, what is the single best thing a person can do to thier head to realize improvements?

3) what do you think of those undercut valves? Is there an inherent stem weakness? Does it improve flow to any signifcant degree?

I am wondering all of this in the context of increases across the hp and torque bands, as opposed to spiky increases/improvements in one small portion of the bands. And in the context of a streetable vehicle, as opposed to your strip monsters.

Thanks, Tom, hopefully you can have a look at this.

Uncle Tail

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1972 Mach1 351C

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