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post #4 of (permalink) Old 03-31-2014, 04:38 PM
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Re: Stroker intake manifold RPM change-PSIG???

I would say your flow requirements will dictate which. Up-front, understand both the VJ and the SV are cast to be ported to the application, as they both have tapered runners for this purpose. Normally, a Vic Jr. would bet he choice to keep as much average TQ and HP through the useful range as possible. Best averages win. So, going to a SV for that last 300 RPM in the traps would normally be an unsound move.

The two factors for you to juggle are available flow and stroker flow. Obviously, if you port to your heads and there is not enough flow to feed them, you have to go SV. Strokers also have need for larger airflow in gulps due to the R/S ratio. While this means bigger is better to a point, you can't use much more than your heads will flow without losing velocity, fuel suspension, and softened torque peak.

So, although we could throw flow numbers around all day, that does not give the dynamic answer we need. Which to choose? I would take a simple view on this, as the port area at about 50% of the tapered runner should equal or exceed your head port area. You would port-match and blend to just beyond the point the areas matched.

Just to add some drama, I would also match flow transition in each runner, as well as port-to-port. This can be done without a flow bench by using a shop vac and an electronic manometer. You can get set-up with one for around $20. OK, kick it back at me.


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