Another head ID

Hey all,
This is a mystery that's been hanging over my head (pun somewhat intended, unfortunately) for years now and the head ID article in the latest Norton News has pushed me over the edge. My head has a casting number of 06-0380 which I have yet to see mentioned in any article I've read about these things. The closest I've seen is a part# of 06-0379 which corresponds to an RH1 head. It also has a 4 (not RH4) stamped into the top, and an "A" cast into the bottom along with "Wells" carved into the bottom which I assume to be the name of someone who worked on it at some point. See pics below:



I was wondering if anyone could help me get a little more detail as to what head I have in terms of compression ratio and such. Unfortunately it's back together and running leak-free, so all I have are these pictures and whatever I can see when it's installed, and I'm loathe to touch anything to make it start leaking again!
I have a gut feeling it's an RH1, but my bike is a 73 750 - was it normal to have early heads on later bikes?

Scheffy.G said:

Unfortunately it's back together and running leak-free

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Together? Running? Leak free? Oh how unfortunate.

First let throw out the possiblilty of this being a Combat head(very obvious). If the inlet ports are 30mm it is probably a RH!. If they are 32mm then it is a RH5, proper for your model and a 8.9 to 1 compression ratio.

Scheffy.G said:

This is a mystery that's been hanging over my head (pun somewhat intended, unfortunately) for years now and the head ID article in the latest Norton News has pushed me over the edge. My head has a casting number of 06-0380 which I have yet to see mentioned in any article I've read about these things. The closest I've seen is a part# of 06-0379 which corresponds to an RH1 head.

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http://atlanticgreen.com/nhth.htm

06-0380 is a pretty common no and can be found on gazillions of heads as it designates the casting and not the machining. Actually it appeared on 650cc heads(I've seen it mentioned on a manufacturing drawing of a IIRC '65 650 head), Atlas heads and several years of Commando heads. AFAIK 06-0379 is a machining of the 06-0380 head (although there's different castings obviously so I might be mistaken on this). Sorry to spoil it probably but there's not really any mystery around your head (the Norton one, that is)....


Tim

I have a gut feeling it's an RH1, but my bike is a 73 750 - was it normal to have early heads on later bikes?

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Does your engine number begin with 22XXXX? Large taillight and black instrument pods? All the '73 750's I have seen had RH5 or RH6 heads. If your engine number is 20XXXX or 21XXXX you could have a '72 with a low compression head that was sold and titled in '73?

You have a very early Commando head (1968-69). This can be easily recognised by the larger "ring" around the exhaust ports, less finning under the oil feed holes, more material at the base of the small fins at the front and generally speaking a more "Flintstone-like" appearance (i.e. untidy casting).

johntickle said:

You have a very early Commando head (1968-69). This can be easily recognised by the larger "ring" around the exhaust ports, less finning under the oil feed holes, more material at the base of the small fins at the front and generally speaking a more "Flintstone-like" appearance (i.e. untidy casting).

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I guess that would make it an RH1, 30mm intake and 9 to 1.