The official line will be that it is safe and accurate to use up to 500psi (34.47 bar). Being a quality product, it will probably be ok if you were to exceed that by 10 - 15% occasionally and for very short periods however that would be at your own risk and unadvisable.
Use a Dial Gauge to get an idea of what these engines are peaking at to make the decision before you put safety and the WPS at any unnecessary risk. Just be sure fuel delivery to the cylinder is paralysed whilst testing.
Last edited by STC
on Sun Nov 13, 2016 5:38 pm, edited 1 time in total.