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Mark (smokey mow)

Smokey's JW4 Formula Four Rebuild Thread

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34 minutes ago, MMB said:

Hi Smokey

Been a while since I checked in...looks fantastic!

Here are a few pics of the firewall I made for my JW4 when I had it. Very simple and rests on the rails and still lets the air flow from the NACA duct under the seat to the engine bay.

All the best

MMB

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Hi Bob, its been a while, I hope you're keeping well.

the firewall on your car was a very elegent solution which I like a lot, thank you for the photos.

for our UK racing regulations the firewall needs to provide a complete seal between the driver and engine compartment to create a barrier against fuel spillage or fire.  On this car the body is from the JW4 Mk2 so lacks the air ducts that were fitted to Mk3 body on your JW4 and my blue car.  The rear engine cover on the mk2 is much lower than the Mk3 so the cylinder head of the engine sits in the airstream for cooling rather than enclosed within the bodywork.

my hope is that a simple flat aluminium closing plate will be sufficent behind the seats cut to match the curve of the body, but I may need to get creative with carboard first to get the shape right.

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A few more small jobs completed today....

The first job was the manual control for the mechanical fuel pump.  Like most F4 cars of the period the JW4 ran a mechancial fuel pump which was driven off a cam on the back axle.  These as you'd expect would work fine when the car was moving but when the car is stationary and therefore the axle not turning there needed to be another way of getting the fuel to the engine. The Pathe videos showed the mechanics frantically priming the pump by hand but as I studied the photos and videos a bit closer many drivers also employed another method so the pump could be controlled from the drivers seat.

the solution they used was very simple which was a bicycle brake leaver mounted below the dash and cable linked to the pump.

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The next job was to make the driveshafts. The JW4's used shafts and hubs of Johnny Walker's own design, however the Carburol Special ran an uprated design for hillclimbing with the uprights machined for BMC Mini stub axles and shafts. Unfortunately the shafts were missing from the boxes of spares I'd acquired so I would need to make some new ones. 

Starting with a par of standard mini driveshafts the length needed was measured and then cut to length.

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I happened to have a pair of driveshaft spiders that I'd had claser cut for the first car but the centre hole was too small so I opened this up to the required diameter on the lathe.

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Mounted back on the car to check the length and now just the welding to complete.

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The final job of the day as the light faded was to fit the battery isolator switch.

I also made a short teather for the key using a length of brake cable and a coupke of crimp terminals so it wouldn't go missing.

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Like the hand priming set up, very clever. I like simple!

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