LS3 Dual Quad EFI Intake Manifold

In a previous post, I was intending to fit the Holley Dual Quad LS cathedral port inlet manifold to the LS3 rectangular port heads by making up an adapter flange, however, this became unnecessary as while I was emailing Holley about some other details to do with the throttle body linkage, I learned that they were prototyping an LS3 version.
Some special arrangements via Summit Racing resulted in me obtaining one.

Holley Dual Quad LS3 EFI manifold part number 300-134

Fitted up with the original LS3 injectors.
Two different sized rail mounts are included with the kit to suit LS3/LS7 style injectors or the longer EV1 style injectors.
New replacement lower injector O-Rings are also included.




The overall manifold sits about 1/4" higher than the cathedral port version.
The fit up however wasn't plain sailing,



Here you can see the manifold doesn't fit up to the stock heads with a gap between the faces.


The overall casting was too wide to fit between the head port machined surface.

There is sufficient material on the manifold to make it fit by machining off a bit of the flange.






In this pic, you can see the edge of the flange overlaps the casting at the top of the head port face machined area.

Set up in the mill for machining.
Could easily file off each flange to fit if required.
I machined a few millimetres off each side of the flange casting.



Finished  mods.

The mounting bolts holes for manifold to head are in perfect alignment and the ports are very well matched to the stock heads.

I'll post some more pics of the injector rail to manifold mounting shortly, forgot to take pics.