I think that cutting the taper,and, bore in the same opperation IS the Key..Stewart is Right, about the Squish ,on, a Hemi head though .The Best working example I can give ,is on my Early mod. Race Sled.Its a 1/2 mile,ice oval Racer.The Engine is a 340 c.c.,Hemi head, Twin Cylinder ,Rotary valve,Rotax,Free air cooled,with dual Carbs,and, Twin tuned exhaust pipes,exiting out of stingers The Engine is ported and polished,The Crankshaft runs on ball bearings,and the Rods are on needle bearings @ both ends..The engine is extremly perticular about it`s "Squish"..It needs to have, exactly 0.006",between the piston top and the "Squish Band" ,at the bottom of the head.If the cylinder head is any closer, Detonation occurs,,,any further away ,and, power is lost.....I have an appointment to attend, this morning,When I get back, I`ll look for my Books,they have some good illustrations ,and explanations, about Squish ,and, 2 stroke Hemis.I`ll scan them ,and upload ,if anyone is intrested in seeing them..Let me know

Andy; Which is the Glow plug,that works best for These Small Norvel adapters..I think I can get, the majority of the O.S.plugs, that are in the chart above,that Stewart posted.,or is there a couple heat ranges, I should get to experiment with?? Part #`s please..I want to order today..Thanks Dave..