Most English diesels of the period had a 2BA compression screw, certainly the Frog 2.49 did.

What is a Tempest LEW? I am familiar with the Taplin Tempest 3.5cc diesel which came with an R/C throttle as standard....being based on ED Hunter components-this will have a 2BA comp screw.....if you are using google to translate a non english name....for a continental or eastern european engine then the comp screw is certain to be metric-and most probably M5 thread.....without posting a picture of the engine in question, we can't positively identify it-and without identification all we can give you is guesswork...

ChrisM
'ffkiwi'

PS a PAW comp screw will fit a Frog 249