Hurumph .

Contrary to popular belief ?? The Double Star , and to a degree , Stalker - are said to pirate their ' specs ' ,
Particularly the DS 60 . Ive a pic of a DS 40 chamber somewhere - essentially ' a bowl ' .
The DS 60 Lite might be said to be a derivitive of the earlier ST 45/51/56 Plain Bearing 'V ' engine .

V Early 'V' 60 I have , dual ring - short rod - has open chamber ( No Squish Band -or minimal ) head .
Im presumeing maybe the Hemi is rather similar .Will recheck the timing on this ,

The Merco 49 ran steady and strong on the ( Original ) ' Stalker ' 130/110 sleeve timing .But little round shaft port .
Might try setting a pdp 60 at the 130/110 timing - for steady four stroke run , perhaps .

Im sure the ' Big Jim ' motors are out there , he mustve done a ton . Wonder if theres any destinguishing marking / engraving
or somesuch .

 

The cuts reduce the buckling of the piston and, from the part, help to wash the bottom of the piston behind the deflector. Useful for non-rectilinear deflectors.

The depth of the cutting is 1.6 mm. 1.7 mm, the angle at the top is 60 degrees.
From the exhaust side a chamfer is removed from the top of the cut to the bottom of the piston. See the photo from the blowdown side for a sharp edge.

can you post some shots of the head