Inazuma Posted October 26, 2015 Share Posted October 26, 2015 Hi allI bought damage b12 engine with crack bottom. I planning to replace only bottom of the crank from my old engine. Is this will work? Quote Link to comment
vizman Posted October 26, 2015 Share Posted October 26, 2015 I'm not 100% sure but I thought crankcases were machined/cast in pairs....so I would've thought not. Quote Link to comment
Suban12 Posted October 26, 2015 Share Posted October 26, 2015 I'm not 100% sure but I thought crankcases were machined/cast in pairs....so I would've thought not.I also think this is true.Was led to believe they are matched pairs.Easier to try and repair the crack if possible. Quote Link to comment
bluedog59 Posted October 26, 2015 Share Posted October 26, 2015 Crankcases are machined as a matched pair. In theory you may be able to use an unmatched pair if the main journals used the same sizes in each case or even if you used the correct shell to match crank to each case................... but I wouldn't unless I was very, very desperateWhereabouts is the crack as they may well be weldable ? Quote Link to comment
Swiss Toni Posted October 26, 2015 Share Posted October 26, 2015 Agree with all of the above, however...try putting the crank and gearbox in the casings, bolt up and torque to correct torque-iness. If all shafts spin with no perceptible nipping up, all should be well..... theoretically!!! Up to you. Or get the B12 cases welded. You can only piss with the cock you've got! Quote Link to comment
vizman Posted October 26, 2015 Share Posted October 26, 2015 You can only piss with the cock you've got!the only other person I've heard use that phrase was one of my northern blue faced brothers..... Quote Link to comment
Swiss Toni Posted October 26, 2015 Share Posted October 26, 2015 (edited) Well....it's nigh on impossible with someone else's!!! And...I am one of your Northern blue faced brothers! Edited October 30, 2015 by Swiss Toni 2 Quote Link to comment
Swiss Toni Posted October 27, 2015 Share Posted October 27, 2015 Oh...as an afterthought...if you do use the miss-matched cases, and everything spins nice and free, check the sides of the casings where the alternator and points covers fasten, in case there's a step. Quote Link to comment
Inazuma Posted October 27, 2015 Author Share Posted October 27, 2015 (edited) So, it's very possible, when iven it will fit that could be leaks. All right then. No chance welding. Looks like one option left. Thanks for reply. Edited October 27, 2015 by Inazuma Quote Link to comment
george 1100 Posted October 27, 2015 Share Posted October 27, 2015 Do not use a mismatched pair even if crank spins. That doesn't mean your tolerances are correct. You may end up with low oil pressure or spun bearings. Don't go there 1 Quote Link to comment
Gixer1460 Posted October 27, 2015 Share Posted October 27, 2015 So, it's very possible, when iven it will fit that could be leaks. All right then. No chance welding. Looks like one option left. Thanks for reply. Why no chance of welding - stick up a piccy of the damage......pretty much 'anything' can be fixed with weld and a good welder! Quote Link to comment
Swiss Toni Posted October 27, 2015 Share Posted October 27, 2015 If you do decide to get the cases welded, take the pair of cases bolted together, to the welder. They should also be pre-heated before welding. Quote Link to comment
nightrider Posted October 29, 2015 Share Posted October 29, 2015 matching the bearing shells would be a nightmare.I'd de-grease the crap out of it and have a aluminum welder specialist have a crack at it. Quote Link to comment
nightrider Posted October 29, 2015 Share Posted October 29, 2015 Plus bearing shells ain't cheap Quote Link to comment
Inazuma Posted October 29, 2015 Author Share Posted October 29, 2015 I follow your advise. I don't know why did this at first place. That' s what oss is for.Should be easy ... Quote Link to comment
Gixer1460 Posted October 30, 2015 Share Posted October 30, 2015 Hmmm its a tricky one but not impossible. Hardest bit is avoiding blocking that oil? drilling at the bottom! I think i'd turn up a stainless, loose fitting plug to fit the smooth section to provide backing to build up the outer weld. You may have to grind out the threaded section and built it back with weld then face, drill and re-tap the treads? Quote Link to comment
Ben Slabby Posted October 30, 2015 Share Posted October 30, 2015 Or weld in a smaller tube and then re-tap it to take another blind plug? Quote Link to comment
Screwriverracing Posted October 30, 2015 Share Posted October 30, 2015 (edited) Or carefully remove the same part from the other set of cases and weld it on.Cheers SRR Edited October 30, 2015 by Screwriverracing Quote Link to comment
Inazuma Posted November 2, 2015 Author Share Posted November 2, 2015 (edited) I pass all yours tips, see what comes up.That is third time in 2 years I rebuild engine.First damage engine it was my foult.Second, the blody painter ad some sand to the engine.So I start again from scratch. Got some bits and bobs laing allaround.Like:Dot head- portedRS 38- bit tired - revs hangingTi headers 42 diaBut I'm not sure going same road. From one hand I have standard healthy b12 engine. From the oder hand I want do that you know power and glory.What I won't achieve is proper bottom power, and of course some on the top. What I have to lose? hmm destroy third engine...What you will do? Edited November 2, 2015 by Inazuma 1 Quote Link to comment
teltwosheds Posted November 4, 2015 Share Posted November 4, 2015 I would have got the lumiweld out already. Cos I'm a tight git me Quote Link to comment
Inazuma Posted November 5, 2015 Author Share Posted November 5, 2015 Looks like It was easyeasy, and cheap.Thanks for advise. 1 Quote Link to comment
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