Head cutting

[KIRCHNER]

just some info that might be helpful had some heads cut. they were 36cc @ 125 psi. cut .035 off. now 30cc and 145 psi; exactly what i was aiming for. 220efi

[NZ Sidewinder]

Some more that might be helpful also.
Cut stock 2.5 fishing heads ( 42 or 43cc)
0.100
Bores plus .020, exhaust 1.575 with promax type chamfer.
Got 145psi

[KIRCHNER]

Some more that might be helpful also.
Cut stock 2.5 fishing heads ( 42 or 43cc)
0.100
Bores plus .020, exhaust 1.575 with promax type chamfer.
Got 145psi chamfer?

[NZ Sidewinder]

Yes
Some exhaust ports have a large bevel across the top lip of the port.
The promax one us large and not just the point of the corner knocked off, it's full depth of the liner material and slopes up a least 45 degrees.
The affect of this is that the piston must move further upwards before it stats to compress air for a comp test.
At speed this doesn't matter, it's actually a performance mod.
But at cranking speed it probably does make a difference to comp readings