Folks,
I understand that A series head studs and/or bolts are 3/8 UNC, but I have a vague recollection that the factory tapped the block 3/8 Whitworth - true or false?
I can't imagine why - whilst they are very similar threads, they are not identical, so this could only have been done to create a slightly tighter or looser fit for the head studs/bolts.
I asked said friend today, and he cannot recall the details, but has a vague recollection that this is the case....

It may also be the case that the factory did these in Whitworth, but any thread work just gets done in UNC.

Thanks for any wisdom.

BTW Mine is an A+ block out of 1989.

Cheers.

_________________
'68 Deluxe w/Metro engine

Block is tapped 3/8"UNC. BMC used American standard threads instead of BSF and BSW, from about 1956 on. In common with many other British manufacturers.

_________________
DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

Thanks very much Doc. Off to find my 3/8 UNC bottoming tap.
Cheers.

_________________
'68 Deluxe w/Metro engine