I’ve had my 1957 Model 88 for a couple of years. It’s in great condition but has an iron head stamped T2140. I’ve fitted the correct plugs NGKB6HS and it runs well, although perhaps a bit of pinking when opening the throttle hard. I’m toying with the idea of fitting the correct alloy head for originality and there seem to plenty about. I only potter about on the bike so I’m not concerned with weight or heat dissipation. Can anyone please advise me on whether there’s much of an advantage to acquiring an alloy head? Presumably Norton thought there was..
Head To Head
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With the iron head, I’d…
With the iron head, I’d venture that NGK B7HS or B8HS are worth a try.
Weak fuel mixture at the throttle opening you are using can also cause pinking: typically slide cutaway or needle clip position. Things get complicated when people lower the needle to compensate for a worn needle jet.
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Thank you Philip, that’s…
Thank you Philip, that’s very useful information - sorry about the delay in replying. I think it’s probably worth me searching for the proper head for the reasons you mention and for originality. Your references will be most helpful.
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Thank you Michael. I will…
Thank you Michael. I will try your suggested plugs before I change anything else. The bike came fitted with a worn concentric which I’ve replaced with a new monobloc 376. I’ve kept the settings standard but, of course, with the different head it’s difficult to know what standard is. I’ve used needle position 2.
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If needle position 2 is the…
If needle position 2 is the second weakest of five, then the middle position is probably worth a try. You’ll soon know if that’s too rich.
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Hi Richard......The T2140 cylinder head that is currently on your Norton is, as you suspected, the wrong one for the model 88. Your bike should be wearing an Alloy T2225 head. However there are actually five versions of this later head including two Alloy versions, an Iron version and two Alloy racing versions.
The T2225 head appears to have been available from 1952 onwards cast in both Iron and Alloy versions. Initially the Alloy head was sold in limited numbers and only to selected owners/racers or fitted to the export Model 88. The same casting number was used on a post-1957 Alloy version which had enlarged finning. This is the version you need for your Norton. See attachments.
The T2140 head was fitted to the first of the Model 7 Nortons sold from March 1949 onwards in the UK. This had a separate bolt-on carb manifold but kept the one-piece spindle/cover of the original 1948 head design . Production of bikes using this head was limited and by the early 1950s it was superseded by the T2212 Iron head. The reason for the change appears to be related to servicing problems encountered when a build up of carbon, inside of the rocker boxes, prevented easy extraction of the spindles. Resulting in the oval end plates becoming too damaged to be re-used without leaking oil. On these early Dominator heads the rocker spindles had to be removed so that the rockers could be moved to allow, in turn, the valve springs to be removed.