Greetings . . .

Hey MBHD - you may have had pistons rated at 12:1 - but with those kind of cylinder pressures your static C/R was more like (220/14.7) ~15:1 at sea level.

Static C/R is simple arithmetic (PSI/Atmosphere). The pressure of one atmosphere depends on elevation - Atmospheric Pressure at Altitude.

Wikipedia says Telford PA is 425 feet above sea level - so 115psi/14.5 is 8:1 compression.

chevyiigul, you indicated that the car runs great until the meth injection kicks in. This could be richening the mixture to the point that the plugs resist sparking. Are the plugs black with carbon? This could be an indication of low spark voltage (cold plug? wires? cap? coil?).

Meth injection is typically used to overcome detonation by quenching. With the cylinder pressure readings you've measured this seems unlikely. Have you tried running it with the meth injection disconnected?

regards,
stock49

[Linked Image from 49fastback.com]