Bearing clearance is pretty crucial.
Cam bearing clearance is probably really one of the more important yet usually unchecked things during the assembly.
re-using a cam isn't a bad thing, especially if it's a roller cam (like ours are). But, the bearing journal diameter should be checked and assured it's in spec even after the polish that the machine shop will do to verify it's size.
Oil pressure comparisons..
'86 6.2.
Rod clearance .002"
Main Clearance .003"
New Clevite Cam, spot on size.
Cold Oil Pressure 70Psi (fac gauge, verified close) 2k RPM
Cold Oil Pressure 60Psi Idle
Hot Oil Pressure 55Psi 2K RPM
Hot Oil Pressure 35Psi Idle
Stock Melling HS55 Oil Pump for a 6.2L
'95 6.5.
Rod clearance .002"
Main clearance .002"
Re-used cam on the low side (best out of the bunch I had)
Cold Oil Pressure 65Psi (fac gauge, verified close) 2k RPM
Cold Oil Pressure 60Psi Idle
Hot Oil Pressure 55Psi 2K RPM
Hot Oil Pressure 30si Idle
GM High-Volume Oil Pump for 97+ 6.5 in a non-oil spray block.
There are some obvious differences.
What I've figured out is that the Cam clearance is pretty important, since it was the only part of the equation that's not "tight" if i had to do it again I'd buy a new cam, with big journals again.
The difference that's also important here is that the 6.5 has the high-volume oil pump and the 6.2 doesn't, yet the 6.2 is making the better pressure.
And one more wrench for the works. A larger oil cooler (HB7) is on the 6.5, so that may contribute as well.
So, to answer the question, is 40Psi oil pressure directly related to having .004" bearing clearance? I'd venture to say that it may.
You're in spec though.
Good that you found the missing bypass valve (for the oil cooler). I'm sure glad that my machine shop always installs those ahead of time, so I don't forget.
J