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+--- Thread: Top of Crankcase Cracks (/showthread.php?tid=5989)
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Top of Crankcase Cracks - Rory Nicol - 22-04-2021
Halfway through undertaking a helicoil thread repair on the vave chest side of the top of my crankcase, somewhat belatedly, I decided to put on my glasses and then saw that there are hairline cracks radiating from two of the threaded stud holes to the adjacent holes in the top of the crankcase that accomodate the cam follower guides.
My gut feeling is that these radiating fractures are likely to be terminal but before I consign the crankcase to the metal recycler I'd appreciate the forum's view.
RE: Top of Crankcase Cracks - bob46320 - 22-04-2021
Could the bores be sleeved to save the block, I don't expect the helicoils would fail due to those cracks.
RE: Top of Crankcase Cracks - Howard Wright - 22-04-2021
Hi Rory
The cracks look to be around the centre of the case? In which case they are close to the centre cam bearing. If the case is special to you (ie matching numbers) then the area could possibly be welded but would then require that centre cam bearing to be line bored. Probably not worth it for a run of the mill case.
Sorry to be the harbinger of bad news.
Cheers
Howard
RE: Top of Crankcase Cracks - Bob Culver - 22-04-2021
Possinbly caused by gasket too thick/soft.Those giant threads are not going to pul out.The crack of concern would be the one above the cam bearing. i had a crankcase cracked at the middle arch and welded eons ago but a lot of distortion and the cam tunnels never aligned properly.The ingenious may be able to devise ways of supporting the cam bore other than welding..
RE: Top of Crankcase Cracks - Rory Nicol - 28-04-2021
Bob, Howard & Bob
Thanks for your thoughts on this. You are correct that the the cracks are close to centre camshaft bearing. The crankcase is not a special number so I shall seek out another, not so easy whilst auto jumbles are not happening.
On the internet crankcases, like human beings, are not necessarily quite as they appear.
Rory
RE: Top of Crankcase Cracks - leaf200 - 29-04-2021
What crankcase are you after?
RE: Top of Crankcase Cracks - Tony Press - 29-04-2021
I think this discussion is about the block not the crankcase
RE: Top of Crankcase Cracks - Rory Nicol - 30-04-2021
Tony
You are correct the cracks are in the crankcase, not the block
Leaf
This is for my 1936 Nippy. Its original crankcase demised sometime before 1972. I'm aware that Nippy crankcases have been likened to dentition in egg-producing domestic fowls, so I will be compromising by seeking out a rubber mounted high frame case.
Rory
RE: Top of Crankcase Cracks - Tony Press - 30-04-2021
"You are correct the cracks are in the crankcase, not the block"
Or even the other way around
RE: Top of Crankcase Cracks - squeak - 01-05-2021
Tony P, refer to the crankcase pictures. Oh they've disappeared !
