1953 / 4 G3LS build
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Re: 1953 / 4 G3LS build
They were very particular at the factory.
Extract below from a very interesting article interviewing the designer of the 1950's AMC 350 engines regarding manufacture and tolerances.....
See here:
http://archives.jampot.dk/editorial/Roa ... _Baker.pdf
Extract below from a very interesting article interviewing the designer of the 1950's AMC 350 engines regarding manufacture and tolerances.....
See here:
http://archives.jampot.dk/editorial/Roa ... _Baker.pdf
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'There is a tide in the affairs of men
Which taken at the flood............'
Which taken at the flood............'
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Re: 1953 / 4 G3LS build
Its common practice with modern engines to grade (measure crankshafts and conrods ) then to selectively fit bearing shells from a range of say 5 grades to obtain the correct clearance , the difference being that on our conrods a outer cage is fitted to the conrod . this is why when you fit a replacement BE assembly you have to 'hone' the outer cage once fitted to obtain the correct running clearance
Id recommend you fit a new BE assembly if you want to use the bike , There are cheaper pattern BE assemblies on the market but we have no experience on there reliability as they are only recently available . If you remember in the 70/80's Alpha tried to change the design and these all failed in service . they had to revert back to the Matchless original design
Id be very upset if I spent all the time rebuilding an engine , only to find the saving a few pounds on the BE made it un ride-able and I had to take it part again
though it pains me to say , sometime you just have to spend the money on the right parts
Id recommend you fit a new BE assembly if you want to use the bike , There are cheaper pattern BE assemblies on the market but we have no experience on there reliability as they are only recently available . If you remember in the 70/80's Alpha tried to change the design and these all failed in service . they had to revert back to the Matchless original design
Id be very upset if I spent all the time rebuilding an engine , only to find the saving a few pounds on the BE made it un ride-able and I had to take it part again
though it pains me to say , sometime you just have to spend the money on the right parts
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Re: 1953 / 4 G3LS build
Spriddler, thanks for that extract. Interesting that the components are graded in tenths of a thou and then paired accordingly.
Peter, I am sure that you are right that the safest approach is to fit new parts. It is just that £354 just for a crank pin was a bit of a shock and the Club parts store do not stock a conrod liner. I am not yet convinced that it is money well spent if the conrod liner is not new as well.
I have a new set of standard rollers and I am minded to order a set of +0.001" rollers as well. That should give me some leeway to have the crankpin sleeve and conrod liner honed a little. In the end although I am going to use the bike it is not going to compete in anything.
Peter, I am sure that you are right that the safest approach is to fit new parts. It is just that £354 just for a crank pin was a bit of a shock and the Club parts store do not stock a conrod liner. I am not yet convinced that it is money well spent if the conrod liner is not new as well.
I have a new set of standard rollers and I am minded to order a set of +0.001" rollers as well. That should give me some leeway to have the crankpin sleeve and conrod liner honed a little. In the end although I am going to use the bike it is not going to compete in anything.
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Re: 1953 / 4 G3LS build
the BE assembly comes with the con rod liner (outer race)
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Re: 1953 / 4 G3LS build
Ahh now I see why you can't go down 5 thou . Every days a school day. However your plan of skimming 1 thou off and + 1 rollers is well worth a try as it might clean up . Don't think it will be perfect though definitely worth a try if only for the sake of your wallet!
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Re: 1953 / 4 G3LS build
If you're fitting 1 thou. oversize rollers, you'll need to reduce the crankpin by 2 thou.ChrisTheChippy wrote: ↑Fri Dec 29, 2023 10:58 pm Ahh now I see why you can't go down 5 thou . Every days a school day. However your plan of skimming 1 thou off and + 1 rollers is well worth a try as it might clean up . Don't think it will be perfect though definitely worth a try if only for the sake of your wallet!
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Re: 1953 / 4 G3LS build
Keep shiny side up.
These are my principles, if you don’t like them, I have others. (Groucho Marx)
These are my principles, if you don’t like them, I have others. (Groucho Marx)
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Re: 1953 / 4 G3LS build
True. 2 thou off the diameter. 1 thou off the radius - a one thou cut. Unless something is skimmed off the conrod liner too!Pharisee wrote: ↑Sun Dec 31, 2023 2:46 pmIf you're fitting 1 thou. oversize rollers, you'll need to reduce the crankpin by 2 thou.ChrisTheChippy wrote: ↑Fri Dec 29, 2023 10:58 pm Ahh now I see why you can't go down 5 thou . Every days a school day. However your plan of skimming 1 thou off and + 1 rollers is well worth a try as it might clean up . Don't think it will be perfect though definitely worth a try if only for the sake of your wallet!
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Re: 1953 / 4 G3LS build
I'm not following this if the roller is 1 thou over, it sits between the crank pin and conrod liner so surely that is 0.5 thou off of each to make the roller fit?EddieDay wrote: ↑Sun Dec 31, 2023 5:26 pmTrue. 2 thou off the diameter. 1 thou off the radius - a one thou cut. Unless something is skimmed off the conrod liner too!Pharisee wrote: ↑Sun Dec 31, 2023 2:46 pmIf you're fitting 1 thou. oversize rollers, you'll need to reduce the crankpin by 2 thou.ChrisTheChippy wrote: ↑Fri Dec 29, 2023 10:58 pm Ahh now I see why you can't go down 5 thou . Every days a school day. However your plan of skimming 1 thou off and + 1 rollers is well worth a try as it might clean up . Don't think it will be perfect though definitely worth a try if only for the sake of your wallet!