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Old 09-19-2009, 06:04 PM   #8
Darin Morgan
Reher Morrison Racing
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Drives: Inferno Orange SS/RS
Join Date: Jul 2009
Location: Arlington TEXAS
Posts: 249
I purchased an LS3 manifold to port. I studied it for a while and found that the only way to fully port it was to cut it apart. I sawed the bottom of the manifold out and made a plate to put in its place. I was then able to port the manifold completely and properly. The sharp edges in these manifolds are deplorable! I understand that the OEM produced this for ease of manufacture and not for all out performance. That is painfully obvious.

I used a router bit to cut this out by hand. I purposely left a lip all the way around to have a place for the cover plate to seal.

Cut out and looking in stock manifold. YUCK sharp edges everywhere!


Not only is there a huge post in the middle of the manifold for support, but the sharp edge leading into the port is what we call a shear. A shear like this will instill vortex generation and eddies in the airstream entering the runner. At higher air speeds the sharp edge will severally limit the runners flow potential, essentially shutting the runner down at high air speed. In other words, the runner is limited just by the sharp edge and not by its area and sizing. The higher the rpm of the engine, more turbulence ensues. This is my primary focus.


Pretty ugly if you ask me. The main problem with modifying the manifold in the shear area is that the manifold is plastic/nylon and I dont know how epoxy will hold. I dont want to use unsecured epoxy to modify the shape of the runner entrance. Not on a street vehicle.

Good shot of posts in the middle of the manifold. These may be good for support but they suck for air flow. Not extreme sharp edge right before the number one cylinder. This cylinder must take air first and it has a DOUBLE shear! One on this wall and one on the side wall. Radiusing this should help this runner a bunch!

More pictures to follow,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, ,,,,,,,,,,,,

2010 Camaro SS/RS IOM, 475rwhp 415ft/lbs Cam-232/245 .612 .612 113LSA. Precision 3500 stall, New Era CAI. Reher Morrison Heads, Manifold and TB. Ferrea H-stems, dual springs, Ti-retainers. American Racing long tubes-Xpipe, High flow CATs, "S"type Borla's. 160F Thermo.
VVT ACTIVE! Thanks to New Era Performance!

Darin Morgan
-Induction R&D-EFI calibration
Reher-Morrison Racing Engines
Phone 817-467-7171
cell 682-559-0321

Last edited by Darin Morgan; 09-19-2009 at 07:19 PM.
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