I have had similar issues to the OP on my newly re-built 428 ... once I had converted Bar to psi
...and I still have to some extent.
- are you using a mechanical or electrical gauge? - the latter notoriously inaccurate.
I found that my engine takes quite a while to properly warm up, and that I was/do hit >100psi (6.9 Bar) at initial start-up, according to my unverified mechanical gauge. After a few mins this falls to 85-90 psi at idle tickover. If the engine continues to idle and warm up, this then slowly falls. However once properly warmed up, the relief valve opens and the gauge falls rapidly down to 20 psi or less at idle. During the summer heat this was quite quick. Now in the winter it can take a while to heat up sufficiently, so perhaps your engine is not warmed up sufficiently?
I still don't like the current high pressure when cold, but will do an
oil change over shortly, as i don't know what grade of
oil the engine was supplied with.