Im sure darton sleeves are tested, and claimed to hold 40 psi, but to attempt 40 psi and a 200 shot???? Youd just be throwing money away... Honestly, Id say 15psi and a 100 shot to start with at MOST, and tune from there...... You can pull more out of it, but to be honest, the most I have seen on a Darton sleeved block is right around 550-600whp, thats why I prefer the GE sleeves that are tried and true, that I see on a car on a daily basis handling 35-40psi.....