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Strange cylinder head

Submitted by ian_burgess on Sat, 08/03/2014
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Heavy Twins

A head I got off ebay to replace the duff one that came with the bike has large exhaust valves and small inlet I have gone through all my documentaison but could not find any reference to a head with big exhaust valves the diameter of the hole is 1.2". The head is identical to the scrap one apart from the ex valve, the scrap one has the number T2225 on it and the new one has T2225M on it. I need valves for it can any one help oto identify it.

Submitted by phil_hannam on Sun, 09/03/2014

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Below except is from 2012 Roadholder. The T2225 head was the first standard production Norton Twin cylinder head to be produced in Aluminium. Earlier Aluminium heads were only available to the race boys. Your head should match that of the attachment. Production dates 1955 to around late 1957.

1955 saw the next most significant change in design and a third version of the head was introduced. This was clamped on top of the final version of the swing arm model 7, the Featherbed framed model 88 and later in the year the new 99 engines. The production head was now cast in Aluminium alloy and is generally marked with T2225 M above the intake rocker cover and/or on the top front fin. Versions of this head had appeared on competition twins in previous years but not been offered to the general public.

Attachments 1955-alloy-head-front-jpg

Submitted by ian_burgess on Mon, 10/03/2014

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Previously phil_hannam wrote:

Below except is from 2012 Roadholder. The T2225 head was the first standard production Norton Twin cylinder head to be produced in Aluminium. Earlier Aluminium heads were only available to the race boys. Your head should match that of the attachment. Production dates 1955 to around late 1957.

1955 saw the next most significant change in design and a third version of the head was introduced. This was clamped on top of the final version of the swing arm model 7, the Featherbed framed model 88 and later in the year the new 99 engines. The production head was now cast in Aluminium alloy and is generally marked with T2225 M above the intake rocker cover and/or on the top front fin. Versions of this head had appeared on competition twins in previous years but not been offered to the general public.

Hi Phil

thanks for that it must be correct as it has polished rockers and the inlet ports are bigger than standerd, but the valvesare the same size,could you tell me the month the artical was in, I have looked but can not find it.

Submitted by martin_rowe on Mon, 10/03/2014

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My 1958 Model 99 also has the T2225 head, with the larger inlet valves. Larger inlet valves were offered as an 'optional extra' for the '59 model (ie. 1958 manufacture). Mine also has the wider spaced (1 5/8" as opposed to standard 1 1/2") inlet manifold studs. Might be worth checking this also to be sure your existing manifold will fit.

Submitted by phil_hannam on Mon, 10/03/2014

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Previously martin_rowe wrote:

My 1958 Model 99 also has the T2225 head, with the larger inlet valves. Larger inlet valves were offered as an 'optional extra' for the '59 model (ie. 1958 manufacture). Mine also has the wider spaced (1 5/8" as opposed to standard 1 1/2") inlet manifold studs. Might be worth checking this also to be sure your existing manifold will fit.

This chunk below is from the same article. It is likely that your cylinder head is a competition special as fitted to the Nomads. The 1 & 5/8 manifold studs are interesting as generally these did not appear until later on heads with a 22707 casting number. This number was also used for the first 650SS heads but these had splayed exhaust ports.

1957 saw another change to the cylinder head with additional finning added between the exhaust ports. This head had more substantial finning at the front that was also no longer stepped. Despite the changes it kept the same T2225 casting number.

 


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