Body Fitting to Chassis

Check list before lifting the body onto the chassis.

Fit heater, brake and clutch master cylinders, pedal box
Do chassis wiring for speedo sensor and neutral switch
Connect the ECU loom and have all the sensors sorted out
Go over all chassis nuts & bolts for correct torque
Sealant or rubber strips around chassis tub rails as per the manual but don't worry about rails round fuel tank
Consider removing bolts in nearside manifold and dropping manifold down on chassis next to engine block

Position the body over the chassis. Hold the rear end higher than the front.
Start with the body to the rear of where it will eventually sit. Be careful of hitting the radiator.
Once past the pinch points, push forward, down and lower the rear of the body into place.
The pinch point is around the chassis rails on a GEN III chassis and the nearside exhaust header. For this reason you can take the header off and leave it resting on the chassis next to the block. It is real hard to get it into position unless it is already there. Once the body is on just lift the header up into place and insert the bolts.
Check the securing holes line up with the holes in the chassis.
A GEN II chassis is probably not so tight a fit.

If you have a body manufactured after around start of 2019 the passenger side footwell was extended to accommodate the pedal box in the case of LHD models. This brings the edge of the footwell in the engine bay very close to the nearside exhaust manifold. It may just be too close for comfort, actually touching, or in my case jammed against the header and stopping the body from seating correctly.

The fix is to remove a section of the footwell:

I have probably taken more out than needed but it had to be all in one piece as I will use what is removed to seal the hole up with some P40







So now we have a gaping hole in the footwell, but it is clear of the manifold and the body sits ok on the chassis. This is important, don't try to flex the body to make it fit and align with the mounting holes. The body is made with the chassis and fitted fine before it had an engine in place.



Exhaust Silencers
We need to think about how the exhaust silencers are going to fit.
There are a couple of options:

Fit the body to the chassis.
Fit the silencers such that there is a finger thickness gap between the silencer and the body, and about one inch gap between the top of the silencer and the door when it opens.
Drill&tap or weld the silencer brackets into place.
Remove the silencers and the body. Now refit the silencers. Fit the cat converter, the 'J' pipe and its flange. Line it all up and tack weld. Now remove and weld it all properly. Fit the body again, fit the exhaust system.

Or:
As above but instead of taking the body off again, get it up in the air and tack weld from underneath.
Remove the exhaust, weld properly, refit.

Or:
Get someone else to do it, especially if you don't have mig or tig welder.

There obviously needs to be a hole made in the side of the body for the exhaust pipes.
I drilled the corners with a hole saw with a diameter that fitted the radius I wanted on the corners. Then used a Dremel cutting disc to remove the section.

The hole is slightly undersized and needs a bit of opening up when the pipes go on. As it turns out, it is also a little high for the silencer pipes when they are fitted.
See here





Finally in place. Note the bundle of ECU loom wires which includes the wiring up from the speedo and gearbox.

Interlude

The Potter's Wheel

Rolling Chassis Video Tour

A homage to AKs video tour available on their web site in the members area.

Rolling Chassis Video Tour
Note this video shows the fuel pressure regulator in the wrong position.
After the body was fitted it had to be moved to the far offside position along the chassis cross rail.
See: Regulator position

I'm not impressed with the auto focus. It was shot with my new Nikon Z50 camera which shoots 4k video, but I used a low res setting to keep the file size down.
It seems not to be as smooth as AK's video, but it shows the chassis complete and ready for body fitting.

Note I have used some neoprene rubber strips from CBS. I blagged this idea from 'Steves AK Cobra Build' blog. Reason is that I hate silicon sealant. But also I will fit the body, hopefully, just the once. But if it turns out to be just a test fitting and I have to remove it, I can. This is very much about the exhaust fitting and I'm not sure how that is going to work out.

Anyway, some pics:

ECU, wiring and Engine sensors

The following applies to an Omex ECU, cable operated throttle and LS3 engine.
I may, if I have any money left, fit a set of Jenvey throttle bodies.
I think they look real horny when you open the bonnet. To have that option, I have to use a cable operated throttle with an Omex ECU. A lot of this will apply to a Canems setup on a LS3 engine, but there will be differences. In particular a fly-by-wire throttle will not need an idle motor. The ECU manages the throttle opening at very low revs. On a cable setup we need an idle motor for the ECU to control air flow at very low revs.

Imagine sitting in the car. Left is nearside and right is offside. So we have no confusion when I say left or right side of the engine. Unlike the nurse who injected the wrong leg with anaesthetic when I was having my titanium rod screws removed.

The ECU loom has all the connectors labelled. They are:

ATS: Air Temperature Sensor. This connects to the little sensor that will screw into the bottom of the air inlet tube between the filter and the throttle body. Use a fibre washer on the sensor so it seals on the curved and chrome surface of the inlet tube.

MAP: Manifold Absolute Pressure. Small black block top right of the engine pointing outwards to the right. It is not used so tie back or remove the cable for it.

CPS: Crank Shaft Position Sensor. Situated at the right rear just above the starter motor.

CTS: Coolant Temperature Sensor. Front left side on the cylinder head. Just above the first exhaust port. Do not remove it, the ECU loom connector goes straight on.

TPS: Throttle Position Sensor. If Omex and cable throttle, AK will have sent you a replacement throttle opening, which comes with a position sensor. It will end up the the left side of the throttle body.

Lambda: Two of these. Oxygen sensors supplied by AK to screw into the exhaust headers, one each side.

Fan Relay: This will need to be spliced into the AK vehicle loom when you get it.

Earth: Figure out where to put it once you have the body on and the rest of the wiring in place.

Dash: As above.

Fuel Relay: You will need to obtain a simple relay, Halfords etc, to wire this into before connecting the other side of it to the fuel pump.

Idle: This is for cable throttles only. Mount the idle motor if you have one on the chassis cross member under the header tank and the air inlet tube. THere will be two hoses coming off it, one to the third connection on the left side of the air inlet tube, and one to a port vacated when the EVAP device was removed.

Fuel injectors 1-8: little connectors on top each cylinder head.

CAM: Camshaft position sensor. This is located low down front left of the engine block. The aperture for it faces downwards. Run the cable for this along the left side of the engine and down behind the alternator.

EVAP: Evaporative Emission Control System. Not used. Remove the sensor and cut or tie back this cable. See; Removing EVAP Sensor

Other sensors on the engine we don't use:
Knock sensors. Big black connectors on midway on each side of the block
Oil level sensor: Yellow connector on the right side of the sump (oil pan if you are from the States).

Other sensors/ports we do use:
At the rear of the block we find a black horizontal port that may have a red cover on it. This is to connect the vacuum tube to the brake servo.

Oil pressure and temperature: Right next to the vacuum tube. Remove any sensor already there and fit the ones from AK.

Second coolant sensor. This is rear right side on the cylinder head just by the most rearward exhaust port. It will be blocked off with a hex bolt. Remove the hex bolt and fit the AK supplied temp sensor. The connection for it will be up to the water temp gauge on the dash board.


Some pics of the  sensors:


MAP sensor, not used


Coolant Sensor front left. Connection is from the ECU loom


Coolant sensor rear right, after you have removed the hex bolt and screwed this in.



Oil pressure and vacuum tube port with the red cover.


Here be the various connectors from AK. Let's number them 1 to 6 from left to right.
Number 2, screws into number 3. Number 3 screws into the cylinder head on the rear right side.

Number 5 screws into number 1. Number 6 screws into the side of number 5. Number 4 screws into the top of number 5.
Number 1 screws into something similar to number 3 which didn't make it to the photo shoot (but it can be sen lurking behind the red thing in the pics above).
Anyway, it screws into the rear engine block next to the vacuum port after the original oil pressure sensor is removed.
Clear? Good.

The thing is that when you come to screw things together you will swear blind they don't fit.
Some of these connectors have a slight conical shape, they will start off the first turn or two and then jam. But fear not. They are the correct thread, just needs a little lubrication and some careful persuading. Even so they will not completely seat together. Use thread lock or ptfe tape and screw in until it all gets too tight to go any further.
The two connectors with dowty washers (one of which missed the photo shoot) need careful tightening. They have a thin wall which can shear off. Use thread lock and tighten to a minimal torque. Don't actually use a wrench but guess at around 10lb/ft or so.


Chassis wiring
Before fitting the body, you'll want to wire up the fuel pump, speedo sensor and reverse switch on the gearbox. Run the wiring on the side or underside of the chassis top tube up into the engine bay. Label them and leave them with lots of length to play with. I covered them with split sleeving for protection.
For the fuel pump, realise that it draws a bit of current, possibly 8, 10 amps or more so make sure you have suitable wiring there. The speedo and gearbox connections are not so intense, being just on/off or signal connections.

On that subject, if you use the speedo sensor in the side of the TKO5/600, it will have two white wires. One is ground, the other is signal to the speedo in the dash. Thing is it doesn't matter which, just ground one, either one, and use the other for the speedometer.

The reverse switch is just on/off so both wires are effectively the same.


Chassis wiring prior to fitting the body.

ECU Loom Routing
If you have a Gen III chassis, the top rail round the engine has its uses. I fed both legs of the cabling for the injectors along the right side, fixed with tie wraps (actually what are called 'flatties' from CBS, looks better than the knobbly ties with a square block sticking out), passed the leg for the left side under the throttle body and then back along under the fuel rail. Each connector has a specific length so it will be easy to see which connector to plug into. There is also a big block connector in the middle for the sparks I believe.
There is a separate leg of wires for the front left coolant and camshaft sensors, and throttle position. These I covered in split sleeving and ran them down the left side of the chassis rail.
Finally there is the connector for the crank shaft sensor down the rear on the right side.
The rest I have bundled up for now and laid on top of the engine while I wait to get the body in place.

The idle motor cable I ran down the right side and across the front chassis cross member to the connector on the motor. See; Idle motor location


Further details for connecting things up courtesy of the splendid folk at AK who I have to say are quite splendid people. Especially when it comes to discussing mince pies.