[GoreMaker]

I mean, that's an improvement... but not nearly as dramatic as I would've expected. Especially not for $400 + shipping to Canada and back. Kinda shows how efficient the OEM design is. I bet a lot of those improvements could be had with very basic hand porting that resembles what the CNC mill does. Too late for me, though... I already shipped my intake manifold to BC

[Formulajones]

Originally Posted by Steve C.

Intake Manifold Dyno Test from SD Performance website.
As always results will be combination specific and vary.

We started with a stock iron intake running a Cliff's Q-jet. After some tuning, we ended up with 515hp @ 52-5300rpm and 575 lb/ft @ 4000 rpm. The next intake was another cast iron unit but with the CNC machined plenum copied from Cliff's personal intake. With some minor tuning we ended up with 527hp @ 5300rpm and 579 lb ft @ 4100rpm.

Test engine: 474ci engine running a set of our 290cfm CNC ported KRE D-port heads with 10.2 to 1 compression on 91 octane fuel with a 236/245 duration hyd. roller cam.


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That part in bold is what I've mentioned time and again. They are pretty good in stock form and will support 500+ HP. I did 507hp and 571tq with an unported 72 455HO aluminum intake, you know, the horrible ones on a smaller pump gas 455 and a set of iron ported 72 HO heads using a very similar 239/243 camshaft. Mine peaked at 3700 and 5500 for tq and hp so a much broader power band to boot.

[Formulajones]

Originally Posted by GoreMaker

I mean, that's an improvement... but not nearly as dramatic as I would've expected. Especially not for $400 + shipping to Canada and back. Kinda shows how efficient the OEM design is. I bet a lot of those improvements could be had with very basic hand porting that resembles what the CNC mill does. Too late for me, though... I already shipped my intake manifold to BC

CNC porting will only get the manifold so far, that's why the gains are minimal.

The ones that support the big power in the fast class are cut apart for porting. That's the only way to get up inside the manifold where a CNC or hand porting doesn't reach. Big money for that type of porting.