A new Big 7

[Parazine]

After spending the last few years on vintage, mag engine Austin Sevens, I have to confess to a relapse. I went along to the most recent Richard Edmonds auction and was beguiled by a very original Big 7 Sixlite.
The car is virtually untouched since it stopped being used by its original owner in 1962, with about 21,000 miles on the clock. The seats are original, complete with “float-on-air” cushions, original headlining, floor mats and so on.


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Sadly, however, the car is mechanically deficient. The engine was started on the day I got it home but continually oils plugs and blows plumes of blue smoke from the exhaust. Oil pressure is good however. The gearbox is noisy, probably the input bearing having rusted during its long storage.
Finally, the rear axle is noisy, inspection show a massive amount of end float on the pinion, which may or may not have damaged it. Probably down to the juddery clutch having “worked” the pinion and fretted the components assembled along it, shortening the spacer and producing the symptom.



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Engine has been removed this holiday weekend and is being stripped down for measuring now.
Potentially, I will need a set of +20 pistons at least for the rebuild with shells, size dependant on whether the crank needs a regrind.
Otherwise, the car drives OK (for a Big 7) on the few brief test runs I took it on. Very reminiscent of the Fourlight Big 7 we had ten years ago; super juddery clutch, positively evil handling characteristics but quite quick on a smooth road, even with a poorly engine.

[David Stepney]

What a lovely find! Once the machanical issues are sorted, it should be a really nice usable little car.

[JonE]

That is beautiful. Does it perchance have a riveted dash plate, or set screws?

[Tony Griffiths]

Big 7. A restored Autocar cover.

[Ivor Hawkins]

What an absolute beauty and wonderfully original, I really like that.

I’m sure you’ll get it back to mechanical perfection and with a little application, the handling can be restored to something rather less frightening.

[Parazine]

The patent plate is screwed on - looks original to me. 

   

The core of the engine has not been touched before, all the tab washers are properly turned over, not hammered. Nuts and bolt heads are untouched by spanners, quite remarkable.

The clutch driven plate is very heavily oiled up, gearbox front oil seal needs looking at I think, would explain the juddering. The box was overfull.....

There is no oil seal at the rear of the engine - just a large thrower. I guess, if the crankcase is pressurising (someone had stuffed a piece of the lounge curtains (1953 style) up the vent pipe), this would also push oil into the clutch area....

[Ilmoro]

Parazine,

I may have some +020 New old stock pistons. I definitely have some +040s. PM me if you are interested.

Ian

[Ian Williams]

Have you actually got the engine apart yet, if the claimed mileage is genuine I would suspect the rings stuck from lack of use more than the engine being worn out. I guess the biggest issue will be how it has been stored, in my experience engines that have not been used for many years often have a fair bit of internal rust, the worst possible thing you can do is start the thing up. I would always recommend an internal inspection prior to trying anything else, head and sump off at the very minimum.

[Malcolm Parker]

Interesting that the patent plate mentions a patent for detachable wheels.  Presumably this is the elongated holes in normal A7 wheels that allow them to be removed without fully removing the wheel nuts?  Strange in that the Big 7 had ordinary steel wheels with normal holes.   It is almost as if Austin thought that there needed to be a patent plate on the dash yet didn't have any patents for the Big 7.   Were they simply using up the ARR Ruby patent plates?

Perhaps this post should be in Patent Plate Minutia!

[Parazine]

Back "in the game" after the North Devon week in the Chummy and a chance today to strip some more of the engine.

The reason for all the smoke and oil fouled plugs?

   

All four pistons had the top compression ring and the oil scraper ring broken. All exactly the same. What on earth caused that? The pistons appear to have picked up too so maybe the engine was overheated, causing a seizure?

Must have happened recently in the cars history as the oil fouling inside the combustion chamber can be cleaned off, revealing normal deposits.

   


Crankshaft appears OK, centre main is about 1/2 thou oval, all the other bearings are on size. Fair bit of rust pitting however but should polish out -  I hope.

I have to own up to breaking teeth off the crankshaft chain drive sprocket though  

   

I think that you're supposed to undo the sprocket on the camshaft, then push the camshaft backwards to free the chain from the sprockets, not try and remove the sprocket from the crankshaft, where it is positioned with a punch mark.     Hindsight - 20/20 vision......

Ilmoro, I will PM you about pistons, I may need a set of +20 and a rebore. I will also need a set of standard B/E and Main Bearing shells and hopefully, thrust washers? Oh, and another crankshaft chain sprocket. Maybe time to contact the Big 7 Register....