1953 / 4 G3LS build

[SPRIDDLER]

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

Component fit 2.JPG

[g80csp11]

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

[EddieDay]

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.

[g80csp11]

the BE assembly comes with the con rod liner (outer race)

[ChrisTheChippy]

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!

[EddieDay]

the BE assembly comes with the con rod liner (outer race)

Oh thanks. It is probably just the photo on the spares web site that is misleading.

[Pharisee]

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!

If you're fitting 1 thou. oversize rollers, you'll need to reduce the crankpin by 2 thou.

[Expat]

[EddieDay]

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!

If you're fitting 1 thou. oversize rollers, you'll need to reduce the crankpin by 2 thou.

True. 2 thou off the diameter. 1 thou off the radius - a one thou cut. Unless something is skimmed off the conrod liner too!

[Duncan]

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!

If you're fitting 1 thou. oversize rollers, you'll need to reduce the crankpin by 2 thou.

True. 2 thou off the diameter. 1 thou off the radius - a one thou cut. Unless something is skimmed off the conrod liner too!

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?