Bill drapers ' Superhawk ' used an Enya 40 SS .
9.600 on a 11 x 6 Kavan prop . 2 1/2 -3 % nitro.
6.75 mm , = 17 / 64 th. in. bore venturie comes
level with bottom of fins at c.l. rounded inside top only.
4 mm spraybar , little O rings to case.
Muffler lugs filed holes out to suit earlier lighter silencer.
Muffler Pressure. Stock head clearance and timing.
This is from a 87 copy of A.M.I. so may be supercedded
Then again , who knows .it may not be .Was spec. then.