I was just given a built up sig magnum and a 80's St 60.  The engine is missing a head bolt and a NVA.  I have a tiger needle valve, but is seems to be a little too short and I and get the collet on it.

So what nva do I need and what size head bolts?

Thanks for the head bolts and the nice letter. 

I have a NVA on order.  Hopefully will get it together by this weekend. 
Just for the record the bolts seem to be standard metric M3 x 5.  So I can use socket head bolts.     

  Fellow's try a 5-40 thread, seems that this one works, of course your mileage may vary..

 I have used them in all my Tiger 60's, no problem

I don't know I took an existing head bolt and a m3 matched up perfectly

Your problem with the ST metric bolts has been around since the first ST came down the line. You can match the threads per inch but you are not matching the pitch. I bought a ton of them from ST back in the 1970's. Then there was a place called Nuts and Bolts on US-19 in Clearwater Fl that had socket head correct bolts and I bought all they had, one box of 500. They are long gone so people found that the 5/40 would work just fine and that is what they use. I have never used them myself as I still have a few of the correct bolts. The flat head bolts that came in the motor were very hard to get tightened all the same. Sockets are much better. Be sure your bolt does not bottom out as all holes are not drilled the same depth.Many times there will be one hole under drilled
Ed

The early ST 60s were 5-40, the later ones are 3mm bolts

Randy

Interesting history , thanks Randy.

Hi John
That also goes for the ST40 , 46 35, the early ones were all 5-40 bolts, just as the old 51 56 were

Randy