Building our AC Cobra 289 LeMan

After seeing Andy Gordons FIA Cobra at the Silverstone show, Mark decided he’d like to modify the peddlebox and weld an extra flange around the edge for extra support as well as getting a really good seal and making it look really tidy inside the engine bay. He stepped the flange back the thickness of the fibre glass in the foot wells so when it is fitted, it will sit perfectly flush on the outside surface inside the engine bay. When we original cut out the hole we stepped it in 1cm to create a flange with the fibre glass. Now this isn’t required, we will extend the hole slightly to the exact size of the original peddle box.


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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

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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.


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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.

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This is something we did a few weeks ago, but haven’t written it up until now. Original we had some real problems getting the exhaust manifold bolts in and tightened up (read post here).

As a possible solution we had sourced some 6 sided bolts from the US in a hope that we could use these and get them on with a simple open ended spanner, but when they arrived we realised the bolt heads were even bigger than the 12 points we already had, so wouldn’t fit. We concluded at this point, the only real option was to take the plunge and to dent the exhaust branches. It wasn’t something we original wanted to do because we were wary of damaging the ceramic coating, but in the end we decided we didn’t have a choice in the matter.

So Mark heated up the problem areas to be dented with a blow torch to get the metal more malleable, then he carefully used a hammer and punch to dent in and create enough space for the bolt heads. The ceramic coating has stood up reasonable well but is slightly damaged in places. It’s something we are going to have to live with at the moment I suppose, although we may see if we can get the coating touched up at a later date.

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We decided to get tickets for the Silverstone Classic Car Show in July. The 289 Register club were going to be there with marquee and display of members cars and as we are new members we thought a good opportunity to meet everyone, have a look at a few finished cars and get some important build tips and ideas. READ MORE HERE

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