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 Post Posted: Sat Sep 08, 2012 7:36 pm 
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Joined: Sat Jul 14, 2012 11:39 am
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head is gmpp sm port vortec bowtie- the cast shape from ex seat to wall is about 20* .25 radius, testing on a scrap head i cut the top cut transition into the chamber and wall with a 15*x .156 radius, this is flattening out the chamber similar to a typical smog head but im getting better forward flow up to .25l/d and less reverse flow with the chamber cut this way compared to the larger radius, both with a 35* topcut , dose this jive with what the more expierienced porters have found,, any drawback,- i would keep the in side the larger radius to help with p/r-, so in the end the in side of the chamber would be 20*x.25 the ex 15*x.156- thanks, tom


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 Post Posted: Sat Sep 08, 2012 8:22 pm 
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forgot to add, foward and reverse testing @44"


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 Post Posted: Wed Sep 12, 2012 9:39 am 
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Haven't done much testing in that area. If the flow is better and the throat area is the same then I'd probably use it. I agree with leaving the intake steeper for p/r.

How does the flow above .25ld compare on the ex?

Rick


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 Post Posted: Wed Sep 12, 2012 4:56 pm 
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what bore did ya test it on ?

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 Post Posted: Wed Sep 12, 2012 7:38 pm 
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above .25l/d the same - 4.155 bore


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 Post Posted: Wed Sep 19, 2012 6:31 am 
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do you have pics of heads ? we copied JoeT./ jenkins for the dart 2 sportsmans were cut that way .if i remember correctly .he used the bowl hog to unshroud them out to the max and hand blended .but they were for 4.04 bore .after the heads were angle milled the chambers ended up at 59.5cc with 2.02/160 . not bad a set of back door jenkins heads redone for 300$

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 Post Posted: Sat Sep 22, 2012 9:33 pm 
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It all depends on the lift you are running or working with. Low lift limited is totally different from unlimited or moderate lift combos. I use 3 distinct/different combinations of radius and angles to enhance the flow at different lift points. I work with the direction/angle of the angle below the seat to direct back flow. The back shape /angle of the valve is also important for each combo. Then you get in a set of heads someone has butchered and you stand there scratching your Head and A** trying to figure out what to do. That happend to me last week. So much fun working on this stuff isn't it?? :~0

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