Magnesium inter cambox

According to to the spares list, the rocker box was the same for 30, 40, CJ and CS1.  The earliest ones had the 4 fixing bolts on different centres.

I take it we are talking Cammy motor?

Measure the centres of the holding down studs. They charged from earlier engines (up to 34 ).  
The earlier bolt centres were 3 1/8". 34 and after we're 3 1/4" centres.  Bolts remain same diameter.  The rest of cambox dimensions remains the same though cam profiles and timings alter.  More pictures would be interesting and what are you building here.  Magnesium camboxes don't normally come alone.... Get your inventory sorted so you know what you have there.

cheers
Jon

Hi Charles,

   Your cambox is a later type as this casting number was used during the 1950s. I see it has 40 stamped on it, but the only difference between 350 (40) and 500 (30) are the cam profiles.