Welcome to my Cobra Replica build blog.
Please contact me if you would like to know more detail as i progress."CR3514@live.com.au"

Friday, September 30, 2016

Engine Started

A big milestone ,
Started the engine, I was expecting the worst, but it fired right up.

The start wasn't without problems though;
Engine was idling at 1900rpm.
IAC didn't function and seemed to get worse.
Rear block off IAC plug was letting air past.
Air leaks from under the quads.
Huge amount of air being sucked through the PCV circuit.
Thermostat didn't start opening till about 210deg, and the coolant spewed out from under the pressure cap shortly after.

Headed back to work to ponder next actions over the fortnight before returning to tackle the issues.

First up was the leaks under the quads, after removing the first quad, i realized that the IAC port machined into the base of the throttle body over hung the inlet manifold.
After looking up the Holley web site, I found they have a plate that installs below the Quad specifically for this purpose, but also that it was supposed to be supplied with the throttle body, a quick search through the packaging revealed them tucked away in a paper envelope the same size as the base of the box, though i didn't realize it at the time.

In this pic, you can see the port overhanging the plate I made to mount the the throttle cable to.

The plate I made to suit the manifold shape didn't cover the IAC port.

Here is a pic of the Holley plate with the extension to cover the IAC port facing towards the right in this pic.

Next up was the amount of air being sucked through the Oil Catch-can and PCV circuit.
After doing some Googling, I found that the original inlet manifold PCV circuit entered the manifold behind the throttle body, so got my old manifold out for an inspection and found the tube internal diameter is 2.5mm, The hose and fittings from the PCV to the catch-can and then to the quad on my setup is -4AN, (1/4" - or 6.35mm).
This was causing way to much air through the breather port on the rocker cover, so i machined up a restrictor to fit inside one of the port fittings on the catch-can.

This is a -4AN orb fitting, which i drilled out the centre to create a ledge for the restrictor to nest into.
The hose fitting that screws on to the port fitting is slightly smaller hole diameter, so the restrictor is locked into place.

This is the Oil vapor separator (Catch Can).
The PCV circuit is located beneath the valley plate on the LS3, then hose to Catch-Can, through the oil separator and back out again to vacuum port on the forward throttle body.

 The restrictor is in the Oil Catch-Can fitting on the left as it exits to the throttle body. (left most arrow)

In this pic you can see on the right throttle body the PCV return fitting.

Also on this pic is the modified Rear IAC port block off plate, with a bolt now threaded through it to apply pressure to the plunger  so air cant leak past.

The most thought provoking fix was the coolant leakage under the cap.
After reading many blogs, I found some information on the LS cooling circuits, including the suggested fix for the LS3 style thermostat not opening.
Basically, on the LS3 thermostat, there is no coolant bypass holes in the pressure by pass plate as on the LS1s., and Ls1 thermostats dont fit LS3 pumps.
The LS3s rely on coolant flowing out the heater circuit on the engine side of the pump and back in across the thermostat on its return to the pump.
I had these ports blocked off as i don't have a heater.
The thermostat would eventually open, but at a much higher engine temp.
The other suggestion on Pirate4x4 was that LS Header tanks should be on the "Low Pressure" side of the cooling system due to higher pressure in the circuit and pump flow pushing the pressure cap of its seat.
My header tank was plumbed straight off the pump outlet.
A Good Read.

So some plumbing changes now have the Header Tank plumbed in to the Heater return port with Radiator bleed and Head Steam Vent tubes providing continual circuit of water over the thermostat.

All coolant problems now solved with the revised plumbing and thermostat opening at correct temp and timing.

Last problem was the IAC.
I tested it as per Holley EFI forum suggestions, by changing the "Parked" settings on the ECU to 0% and then 100%, the IAC didn't budge from about 50% open, and when the engine was running, the IAC would read as closed, but would hover around the 20+% open.

I was thinking Holley IAC, Holley Wiring Loom, Holley Dominator EFI, should work together until it dawned on me I had an LS2 spec loom and so it would be to suit a GM type IAC.
This was confirmed when I found that the Holley IAC is a Chrysler type. A check on the wiring diagrams confirmed the difference between the LS2 and Generic Holley looms.
Same Connector, Delphi 150.2 4 pin, but the pin assignments are different for the stepper motors.

A simple change of pin locations on the Holley Dominator P1B connector on the loom and the IAC was working perfectly.

I changed the pin positions on the ECU end as the pins remove very easily by pushing a locking tab and then pulling on the wire.

The Delphi 150.2 plugs however are a pull through wire type connector and  i would have had to get new terminals and rewire.

I also finished my aluminium version of the inlet tray,
Mark Nugent from www.marknugent.com.au made it using the fiberglass part I made awhile back as a buck.
I thought the fiberglass part looked a bit heavy but I was happy with the shape and overall look.
Marks work is simply amazing, checkout his Web page, Facebook page and Youtube.

 Set the part up on the router and cut the location mounting holes.

So..... here it is, some video of the engine running.