Building our AC Cobra 289 LeMan

Over the last week Mark has been busy making a specially made bracket to mount the coil to the engine block. He started by making templates from cardboard before marking up the shapes on aluminium. Then using a hacksaw cut them out and filing down to get the exact shape, always checking the bracket fitted against the engine. He then marked the bolt holes and drilled them out. To do the wield we used our uncle Dave again who helped us TIG wield the pieces together. Final job was to tap a thread in the holes for the bolts, file down the wield smooth and polished it up nice and shiny. The coil is now neatly positioned to the side of the block next to the distributor.

—

Why not share this:

Starting 1st time

We got a temporary 5 litre tank of petrol from the garage round the corner and put the end of the fuel line in ready.

Mark then connected the fuel pump, coil and starter to the battery. The fuel pump then started pumping the fuel through the lines. Mark then made the connection from battery to starter motor and after a couple of coughs, WOW, Cobra 5litre V8 comes to life, what a noise! As expected it was massively loud, especially as we only have the exhaust downpipes connected right now with no exhaust. We gave it a couple of starts and it seemed to start really well. Mark also blimped the throttle a little to give the engine a bit of rev and it really showed the power we’ll have under the hood.

On the second start, the Cobra decided to bite back a little, the carb backfired slightly at one point when revving it up (as you can see on the video clips below). Mark singed the hairs on his arm, but he’ll live! We guess the backfire is because the timing was to far advanced, but the timing is something we just need to sort out a little so that it’s spot on with the timing light. Hope you enjoy the video clips!!

Starting 2nd time – Cobra singes Marks arm

Why not share this:

We were then onto fitting the distributor. We fitted the rotor arm to be TDC (top dead centre) for number one cylinder. See diagram for the configuration of distributor cables to cylinders.



Next was to route the leads, chop them to length, fit them neatly on the spark plugs and then fit onto the distributor cap. We also labeled each lead in turn with the corresponding cylinder numbers. Eventually we will heat shrink the number labels once we have fully timed up the distributor with timing light. We have decided to fit a ballast coil and this requires a ballast resister to be used. This is wired in to the positive side of the coil and reduces the voltage going to the coil which keeps a more stable voltage when the engine is running.


–

Why not share this:

We decided we’d really like to get the Cobra started before we get the body back on.

First job was fitting the oil Pressure gauge to the end of the pipe which runs to the adaptor that we fitted to the oil pressure switch out let in the engine block a few weeks ago (Read about that here). Then we connected up the fuel filter and fuel pressure regulator and the fuel line to the carburettor. Next we fitted the oil filter and fill the engine and gearbox with oil.

Before we fitted the distributor we connected a drill to the oil pump drive through the distributor hole and with the drill running in reverse we drove the oil pump and primed the engine. Also now that we had the oil pressure gauge connected we could make sure the pump could produce oil pressure before starting the engine.

Next thing was to fit the distributor, coil and the ballast resistor to do this we made a temporary wiring harness. We went for a Hall Effect distributor which does away with the points and condencer. See next post (Starting the Engine – Part 2) for fitting the distributor.

—–

Why not share this:

Mark got the new oil pressure switch and oil presure gauge today from Real Steel and went about fitting and installing to the engine. He used PTFE tape wrapped tight around the threads giving a really good tight seal on the joints. It then screws directly into the block and fitted the oil pipe connection on the top that will eventually run up behind the dashboard to the oil pressure gauge. The wire for the switch will connect into the end thread and also up to the dash. We’ll wire up the oil pressure light later. 6 pics show his steps.


This is and extra bit I’ve written, following on from Aaron’s comment about checking that the sender has a good electrical earth.

As he pointed out, the body of the switch has to earth to the engine and when there is no oil pressure the contact in the oil pressure switch should be closed and therefore there should be 0(zero) OHMS (or close to Zero OHMS) resistance between the centre switch contact and the engine. When there is oil pressure (i.e when the engine is running), the contact is then broken in the switch and would then turn the light out. So if the PTFE tape was stopping the connection between the body of the switch and engine then the oil light would never come on.

There is a simple way to check there is a good connection. Simply using a multi-meter and switching it to OHM’s resistance, then without the engine running put one lead on the end connection of the switch and the other lead on the engine (as on pic below). You should see round 0(zero) OHMs. If the resistance is too high then you may need to remove some of the PTFE tape so that you get a good seal but also a good connection.


Thanks to Aaron for contacting us and pointing this out

——–

Why not share this:

We received the exhaust back from Camcoat who had done the ceramic coating. This acts as a thermal barrier and will stop them corroding and but more importantly make them look really nicely shiny and blinged up. We opened the box and initially we were really pleased with the result. Don’t they look great! Maybe we spoke too soon!!!

-

Exhaust problems

We were really keen to get them on the car ASAP. So straight to work…. Suddenly we discovered to our horror that some of the bolts were too tight up against the exhaust branch, making it very difficult, if not impossible to get a socket or a spanner on them to tightened up (as you can see from the pictures). This is possibly something we should have checked before sending them for ceramic coating, as at that time we may have been able to dent them in slightly to give more room for the bolts. If we do this now we are concerned we may damage the coating. So we realised we’re going to have to get thinking to find a solution!!! First thought would be to modify the spanner, perhaps by grinding down the wall. We’ll keep you posted. If anyone has an idea please let us know!

—

Why not share this:

A spacer is needed for the bracket holding the clutch release… we  fitted it all together first to get the correct distance required for the spacer and get the position of the brackets correct.

We then found that the edge of braket and the outer bolt for slave cylinder was very close to the chassis. So we ground down the edge of the brackets to match the edges of the slave cylinder, just to prevent it from hitting if the engine kicked.  Also the second part of the braket was pushing in on the rubber of the slave cylinder so to stop this from happening we also ground it away slightly to give it better clearance.

We disassembled it all, repainted the brakets after grinding them and then got to work making the spacer from a piece of aluminium on Uncle Dave’s lathe. Then reassembled again with spacer and then finally connected the pipe.

-

Job done.

Why not share this:

We received the exhaust manifold and down pipes, we ordered from Gerry. The pics show both sides loosely bolted to the engine.
The problem we noticed was that the down pipe was sitting very close to the engine mountings. This is not good, and after speaking to Gerry, we established they had been wrongly made so he is sending replacements. More on this in later posts.
We are also looking into getting the manifold and pipes ceramic coated which will act as a thermal barrier and stop them corroding, but more importantly make them look really nicely blinged up.  More on the exhaust in later posts.

Why not share this:

Gearbox next. – The bellhousing had to be modified slightly by drilling two holes in order to fit the clutch fork mounting pivot. We sent this to Gerry a few months ago as he has a special jig for this.
The gearbox is then bolted to the Bellhousing and the clutch fork (with pivot mechanism) and throw out bearing are installed. The gearbox and bellhousing are then put together with the engine and clutch. This went together quite easily.
The bracket for the hydraulic clutch mechanism has to be put in place - more on this later.
Finally we fitted the starter motor in place.

Why not share this:

Next was splash plate and then the Flywheel. Firstly we spray painted the splash plate silver before putting it in position and installing the fly wheel. Before the fly wheel is bolted on, it’s best to press in the dowels for location of the cluch cover. They were quite tight so we used a rubber hammer to get them in. All torqued up to 85 ft/Ib using Locktite on all the threads. You also need to lock the flywheel to enable you to get to the torque when tightening up else the flywheel turns. We simply wedged a lever bar between the gear box bolt and ring gear which worked fine.

Next was the Clutch plate the clutch cover. The clutch plate can be aligned using a alignment tool but Mark managed to align it by eye, fairly easily with a bit of fiddling. Then torque up the clutch cover bolts to 36ft/Ib (opposite to opposite), job done.

Why not share this: