NH 350 LOWER ROCKER SHAFT SHIMS?

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IainClark
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NH 350 LOWER ROCKER SHAFT SHIMS?

Postby IainClark » Tue Dec 22, 2015 10:37 pm

Hi, rebuilding a 1957 NH 350 basket case, engine was totally striped when purchased, when fitting camshaft and lower rockers, looks like there is a shim washer supposed to be fitted behind rockers to crankcase? is there one to be fitted on the outside of the rockers? just that there are two shim washers the same size in the box of parts? :?
thanks, Iain..............

Simon.Gardiner
Holder of a Golden Anorak
Holder of a Golden Anorak
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Re: NH 350 LOWER ROCKER SHAFT SHIMS?

Postby Simon.Gardiner » Wed Dec 23, 2015 11:09 am

The shims are to centralise the followers on the cam as well as reduce end-float, any adjustment needed depends on each crankcase/timing cover combination (assuming the gasket thickness is a constant :) ).
Usually (from what I've seen) the shims go behind the followers, yours could have the clearance being taken up by two shims the same size. It's probably not as critical with the single-lobe cam and in any case it's also relatively easy to move the cam bushes slightly, which can effect where the cam runs (there are also shims available for the camshaft, to reduce end float, but many people just close up the bushes slightly to get the same result).
(I've seen more engines without any shims than with them so I'm not sure that it's necessary to lose a lot of sleep over it unless there's a big disparity in the positioning of the components - but maybe trying to line it all up would be a pleasant diversion from the usual Xmas mayhem :lol: )

SG
'55 Huntmaster, '56 VH, ' 51 VH, '80 R100RT, '00 Sprint ST (but all those Ariel parts can only make one running bike...)


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