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So I’ve got one of these big dogs porting intakes here…

15691 Views 208 Replies 38 Participants Last post by  96pushrod
A kind gentlemen - who is not big dogs, or affiliated with them sent me a big dogs cobra intake that has been ported. I’ll be replacing the box r intake on the car temporarily to see the difference.

I won’t get into the pissing contest, really here as a third party to make a comparison. Here are some pics of it compared to a factory explorer intake. All measurements are in mm.

This will be a strict a to b comparison deal. I’ll look at fuel flow and dragy times to see which one works the best. Engine is a woody built 347 with a f1r blower. Any ideas on which will come out on top?

If anyone wants any other pics or measurements, please Let me know and I’ll oblige if I can.

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Definitely reverse taper there........but let's see. We DISCOURAGE porting any GT40/Cobra/Explorer lower beyond a 1250 size head port but we get a lot of requests for 1262 - we try to discourage that and suggest better alternatives. I'm thinking Tony cuts length out of the upper to make up for larger cubes when a more appropriate intake suggestion is more in order. Kudos for the test 96pushrod!
That's what I worry about with a ported lower, how does it flow versus the upper. I'd like an intake ported for my 347, not an Explorer(I have one from you already), but hopefully with thoughtful care about tapering the ports sizes from the inlet and down, somewhat evenly.

I have an untouched Explorer upper plus that lower, and a used raw Edelbrock RPM II, and the one I want ported to use.
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How do you figure? If the blower makes power at 11psi, and the intake change increases to something like 13, does that not prove a restriction?
Of course there is a difference, but it's extremely hard to accurately compare the differences when using boost. A 40cfm difference in heads should make a huge difference in a NA engine, but with 10-15psi boost, the change is likely to be minor. The intake is critical for a NA engine, but comparing a 5500rpm intake to a 7000rpm intake, with boost in the same rpm range, shouldn't be earth shattering.
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I think most of this or any plans or testing, is the choice we make of the ideal, versus the best we can come up with for a given budget etc. You can mix up all kinds of intakes etc, throw different boost at it, and end up near the same power levels for the given application. Most of these discussions are about hitting the highest power levels or the limits of the parts.

But some have imposed limitations such as the Cobra intake being required for the car. My SUV project is similar, inherent limitations of the exhaust and engine bay space, 4500lbs, street tires, and wanting 500rwhp in a platform that's never reached a documented 400rwhp. I'm planning to use parts that in a Fox Mustang, could hit 700 easily. But rpm limitations and street driveability, AWD and four identical tires, it'll be adjusted to be as reliable as possible. So the parts have to be selected to hit the goals and still meet the needs of a DD.
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After reading page 6 I was going to say theory argument is cute let’s see some dyno numbers but Tmoss lays out some result goodness on the table.

So what’s the overall goal here comparing? What’s superior to a certain RPM? Average power? I feel like you can port a factory intake all day but if you want to turn 7k or more a stock style is a horrible way to get there.
Exactly, every intake will have an inherent rpm band where it will be the best. The stock intakes will be best for low rpm ranges, the GT40's seem to all shine from the cruise levels around 2000rpm and up to the 6000 level for smaller SBF's. The aftermarket intakes all begin at higher rpm's than the GT40 or stock versions, and they reach well over 6k easily.

I'm in the same boat as the car that began this testing(363 with Cobra intake), wanting best street rpm power/torque, and still reach 6k or so shifts. I bought an RPM II for that on my 347, but still I recognize the advantage of the GT40/Explorer intake I could use. Then I remembered that I had bought a slightly used BBK intake that everyone hated back in the day, and if fixed right it could be better than the others for my combination/car. I don't want a reverse taper ported intake, but maybe a decent attempt and work on the upper and lower.
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