Cylinder heads

hello this all depends on what engine is going on   as cylinder heads are machined to one model or another  and  head number  23166 is machined for four  different  models  from 500 to 600 to 650 and 750  so now you see the issues  here    yours   anna j  

Is it possible to supply the torch settings and the order of tightening the head as I am rebuilding it completely from scratch. This is new seats, guides, re-cut, valves and so on including being skimmed. Also any advice on pitfalls to avoid?  

Check technical pages under Heavy Twins.

Peter:

I believe that you have been bitten by the auto spellcheck monster.

Certainly, no one wants to torch their Norton.

Mike

Jonathan .....as follows is a little more detail about the 23166 Norton cylinder head. This was primarily designed as the first generation of 750 cylinder heads to go on the Atlas engine. The key difference in external features being the 5/16" head bolts each side of the spark plug and the repositioning of all the head bolts behind the spark plug. These moving about 2mm to the rear. Both of these small changes being the reason for the need for a different head cylinder gasket. The inlet valve was larger at with a 1.50" dia head. Up from 1.406" for the 650 head.

Inside the head, behind the inlet valve, seat is a large crescent of metal that sits between the barrel spigot recess and the valve seat.

When Norton Twin production moved to Woolwich/Plumstead the 750 cylinder head casting blank was also used for the 650 engines. This kept the old 3/8" head bolts, headbolt positions and previous inlet valve size and spigot positions.

The attachments show the differences between the two heads. It is possible to bodge the head bolt holes to enable fitting to either 650 or 750 barrels but only if the spigots are removed or not there in the first place. Not recommended!!!

It was claimed that the heads were cast around the assembly of 13 cores. The cores were no doubt named or numbered. The individual core were likely not always embossed with a core marking. In the beginning days, it is now obvious that the different heads were made from different evolving cores. This is evident as the part numbers changed.

The final heads were assigned part numbers that were NOT based on 1/13 (one core) whether for example, skull core T2140-T2212-T2225-22707 or bottom fin core 23166 25319.

The SS downdraft head first used on the 60 manxman and all later 650, then the 62 88SS and are the first 40 degree exhaust port heads replacing the early 20 degree exhaust port heads. For the most part, the head did not change much going to atlas application except the bolt pattern size to accomodate the Desaxe effect plus a bigger intake valve

The final result is that none of these core marks were used as the actual norton head part number.

Measurements of key identifying characteristics is the most accurate way to identify a head.

http://atlanticgreen.com/nhth.htm

here is my head 650 ss ,1964

https://freebiker.rajce.idnes.cz/hlava_650_SS_norton/