Thread question

[Geoff Butcher]

There's a threaded hole on the back end of my block where a stabiliser bar is sometimes fitted. It's in very manky condition, so can anyone confirm what thread it is, before I do something rash, like run the wrong tap down it?

[rocketron]

Dear Geoff, Just checked the 2 threads which secure the stabiliser bracket on 4x1275 blocks: they're all 5/16th UNF. Convention usually has coarse threads into cast iron, but in this instance deffo 5/16th UNF.
Best regards, Ron

[Geoff Butcher]

Thank you!