Had a chance to investigate this LT1.
Driverside valve cover access:
Never been touched and it is missing a valve cover bolt - odd:
Quite the valve cover baffling:
Blue Grass tool...works pretty good:
Springs are quite pretty:
BTR's installed:
I spent time measuring both the installed height and pressures related. Using my not exactly the best tools (spring micrometer did not fit the narrow LT1 spring pocket...defaulted to a metal ruler and 14 year old eyes.
With the OEM spring seat/seal combo - installed height is 1.9375 inches.
OEM spring seat pressure: 94
Over nose of intake lobe: 304
Over nose of exhaust lobe: 294
BTR's setup includes a thicker spring locator and the valve locks are .050 lower - decreasing the installed height to 1.8875.
BTR spring seat pressure: 124
Over nose of intake clobe: 328
Over nose of exhaust lobe: 324
I elected to include a .015 shim under the intake spring...bumping pressure a touch to fully offset the ~11 psi boost:
BTR with .015 spring seat pressure: 128
Over nose of intake lobe: 342
Hopefully the other 14 springs replace as easily.
Note: putting the engine at TDC only allows the valves to drop quarter of inch or so (more on the exhaust side). No air or rope trick required.
Desire is to return to 6500 shift points and possibly 6800 when required.