Inlet Manifold - 2

(Mod - See future post for change to LS3 Dual Quad Inlet manifold)

So, searching the web for port diagrams displaying relationship to manifold bolt holes or even comparisons of the difference between Rectangle Port and Cathedral Ports on the LS engines doesn't turn up much good info other than photos.

First step in determining if I can port match was to get some accurate measurements from the LS3 heads.


This shows the right bank.
If you look carefully, you can see that the ports aren't parallel to the block face, they are rotated about 2 degrees

Next step was to lay some card over the ports and tape in to space, then using a tack hammer, tap around the edges of ports and manifold locating bolt holes effectively cutting through the card without damaging the head face.

In this pic, you can see where the furthermost front locating hole is punched through the card.






Next step was the manifold purchase.

There is a story that goes along with this purchase that further reinforces my belief that Australian retailers are a rip off and offer lousy service to go along with it.







Nice looking casting until I noticed the manifold is faulty.

Yes, that's where the mill cut through the side of the lower dual plane port into the upper port while machining surfaces,

How this type of defect gets through inspection, I'll never know.






Here's the view from the opposite port.
I understand these things happen, and had the process to replace been quick and efficient then no problems, but the hassle to get it replaced was ridiculous.


This is from a major Australian performance parts supplier, they should change their name from Eagle to Turkey.






Same process with the Manifold Ports.












After profiling the ports, I could overlap the ports to see the variance.

I micrometer the parts and verified on the cut outs then overlapped the measurements in CAD










Here you can see the variance in the overlapped ports when mounting holes aligned.
The blue areas are the Cathedral Port.
The grey groove is the port seal groove in the inlet manifold around the cathedral port.

The Red area is the LS3 rectangle port profile that would need to be machined from the manifold to match.
The dark blue area is where the cathedral port would need to be filled to match the rectangle port.


There appears to be enough material in the manifold flange and port wall thickness to easily achieve the match, but the machining of the port would come right up to the edge of the seal groove.
Some compromising will need to be done if I head down this track, with a few millimeters of clearance to the seal.
Considering the CFM flow of the manifold is rated at 700hp, and my target is 500hp, should have some scope without restricting airflow.

Before













In Progress










More to follow.