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A new Big 7
#10
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  Blush

   

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....
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Messages In This Thread
A new Big 7 - by Parazine - 04-06-2022, 11:29 AM
RE: A new Big 7 - by David Stepney - 04-06-2022, 11:35 AM
RE: A new Big 7 - by JonE - 04-06-2022, 12:04 PM
RE: A new Big 7 - by Tony Griffiths - 05-06-2022, 02:02 AM
RE: A new Big 7 - by Ivor Hawkins - 05-06-2022, 09:43 AM
RE: A new Big 7 - by Parazine - 06-06-2022, 10:35 PM
RE: A new Big 7 - by Ilmoro - 06-06-2022, 11:50 PM
RE: A new Big 7 - by Ian Williams - 07-06-2022, 06:41 AM
RE: A new Big 7 - by Malcolm Parker - 07-06-2022, 07:00 AM
RE: A new Big 7 - by Parazine - 18-06-2022, 11:45 PM
RE: A new Big 7 - by Hugh Barnes - 19-06-2022, 07:46 AM
RE: A new Big 7 - by Parazine - 24-01-2023, 04:49 PM
RE: A new Big 7 - by Ivor Hawkins - 24-01-2023, 05:58 PM
RE: A new Big 7 - by Austin in the Shed - 24-01-2023, 07:50 PM
RE: A new Big 7 - by Dave Mann - 24-01-2023, 09:40 PM
RE: A new Big 7 - by Peter Sweeney - 25-01-2023, 12:39 PM
RE: A new Big 7 - by Parazine - 22-05-2023, 06:17 PM
RE: A new Big 7 - by David Cochrane - 24-05-2023, 04:32 PM
RE: A new Big 7 - by Tony Press - 24-05-2023, 11:47 PM
RE: A new Big 7 - by Jeff Taylor - 25-05-2023, 08:51 AM
RE: A new Big 7 - by Parazine - 25-05-2023, 11:37 PM
RE: A new Big 7 - by Tony Press - 26-05-2023, 03:06 AM

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