Diameter of cam bearing to rockers oilway drilling?

[sparky_spit]

I've finally found some time to start arranging the crank regrind (see 

) , assuming the machining company is now open and does not have a year-long waiting list.  I've been doing some bits and pieces in readiness was checking various things when I remembered the mod that had been done to the oil feed up from the rearmost cam journal and through the head to the rockers. When the PO had this engine rebuilt by (or maybe farmed out by) Clive Manvers it had a 1/4" copper tube inserted into the drilling in the block (using Loctite) which then stuck up above the surface of the block and into the drilling in the head by about 3/8". This was presumably to help get an oil-tight seal at the head gasket interface.

I'm in two minds whether to keep this or not. The question is whether the original drilling was already 1/4" or has it been drilled out from a smaller diameter?  The copper tube has a wall thickness of 1/32" so the "hole" is effectively 3/16" with it in place, and more than enough oil gets up to the rockers already.  Anybody know what the standard size is for this drilling? 

[PeteStupps]

Evening. Just checked on my 1296 and 1147 blocks and they're both 1/4" bore. 

Pete

[Nick Jones]

Good man...... that saves me going out and measuring mine 

[sparky_spit]

Many thanks chaps...