What serial number?
Mine is Australian made and I have had it for around 12 years. I bought through Mick Hemmings in the UK when he was the UK agent. I certainly thought it a thing of beauty when I bought it and it saved me waiting 12 months for Steve Maney to get an original item one prepped for me, which alongside the cylinder barrel and rocker arms would have been the only used parts in the engine. The porting on inlet and exhaust was developed by Jim Comstock and it is very effective
It is on a 750 short stroke in a race bike, but has standard valve angles and sizes, skimmed 20 thou.. It works very well coupled with a PW3 profile (Now a JSM version) and a bit of compression (around 10.5:1).
I am guessing that is what you have. A more recent product will have been made in the US.
Some say the alloy used in the Australian one was soft, but in fact they were made by different foundries in small batches during the production life, so I believe that varies. I can see some signs of softer material, but I still think it is 100% better than an original Norton casting. If you pull it off see if the main 3/8" bolts have sunk into the head at all, that seemed to be the symptom that was mentioned.
I have had to put inserts in for the studs. But, of course, it has been on and off more times than would be the case with a road bike.
Definitely money well spent. I'm happy with it.
If I was flush with cash I might be interested in a US made one, which by most assessments is better quality both at the casting and machining execution, I particularly like that it has inserts for the studs as standard. The design itself is the same and was developed in Australia with access to original drawings owned at that time by Mick Hemmings.
