Inlet manifold - 3

Home for Christmas this year, and Mr. Postman had turned up with some boxes for me with some goodies to play with over the next few days.

A quick un-box, out to the shed, sit them in place, stare for a while.

Starting from the Top,
Twin Stelling & Helling 8-1/2" Chrome Air Cleaners.









Twin Holley Billet Throttle Bodies,
Part # 112-577,
1000cfm, 44mm bores, with either 1 to 1 or progressive secondary bores.
Comes with IAS and TPS.
Ports for Evap Solenoid and other vacuum or atmospheric devices.






Under the quads sits a 1" bored spacer,
While they purportedly improve torque, i purchased them to bring the height up enough so that the air-cleaners would be visable through the bonnet scoop and the engine would have an overall height in proportion to the original carby heights of about 3 ", the EFI quads are about 2" in height.



Next step is to design the MAP Sensor Mount, and Evap Solenoid Mount, Evap Solonoid Piping to connect up with canister line.
Machine up adapters for the small LS3 EV6 injectors to fit the space normally occupied by the larger LS2 injectors.
Make a Dual Quad Linkage, and a throttle cable mount.
Make a jig to hold the manifold and a port face plate so I can accurately match the ports between the Cathedral Port Inlet Manifold and the LS3 Heads.
(Mod - See future post for change to LS3 Dual Quad Inlet manifold)
Air cleaner plenum tray to fit between the Quads and the Bonnet.
Put Studs in the Heads instead of inlet manifold bolts, and studs in the manifold carb flange in place of bolting the Quads on.

Have a great Christmas all.

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.

Inlet Manifold and Throttle Bodies - Prelude

The more Cobra pics I collect, the more I love the old school look..... Twin Carbs.
But, I love the modern tech and modern materials as well so I'm going with the retro look of  dual quad throttle bodies.

This is one of my favourite Cobra pics, Ken Miles's number 98.
Particularly the shroud surrounding the air cleaner,
It seals up against the underside of the hood.

I also like the twin air cleaner look of the original Stelling & Helling filters with the chrome tops, should look good nestled between some carbon fibre and billet bits.











This is the look I'm going for, modelled in Sketch-up, it gives me some perspective on the overall dimensions and look








There are a few manifold candidates for the LS motors from the big names like Edelbrock, Holley, Wilson, etc etc, in Single and Dual Plane and also some custom manufactured versions, but the high riser singles are too tall and don't have the right look for me.
So, I've settled on the Holley Dual Plane Mid Rise Dual Quad Manifold #300-121,
This was because of the excellent flow rates detailed in several on-line magazine comparisons.



This pic I took off a You-Tube clip when I was trawling for throttle body candidates.
Its the same manifold with twin 1000cfm billet quads, also Holley part #112-577

The fuel rails come with the manifold.






The issues with this set up is that the manifold is made to suit Cathedral Port heads,
My engine is an LS3 with the Rectangular Port Heads.


The 2 options I'm looking at for this is:

option 1. Port match the manifold to suit the heads if possible, initial measurements suggest i can get very close to the same cross section so flow and pressure differences are similar, by widening the Cathedral port and adding some fill to the base of the cathedral port to match heights with the LS3 heads,but,
if there isn't enough material in the side walls of the manifold, then,
option 2 is to fit a pair of Mast 245 heads that have similar port lengths and combustion chambers but with Cathedral ports.

More on my efforts in the next post