After setting this aside for a time to focus on other things on the car I was finally able to circle around back to it. There was an issue with 2 cylinder's having their pushrods loose. As a precaution to make sure there was no rocker arm or pushrod nonsense going on in the future I elected to replace all of them with appropriate brand new pushrods and rockers. I went to replace one set, I checked before removing and the original wasn't loose at all, very firm. After putting the new lived up pushrods in and new SBI rocker arm, I torqued it to spec.....and it was loose. Did I not install this correctly? There's no way it's a lifter issue but I'm really at a loss to understand what went wrong......

 

Lifters bleed down over time, causing the pushrod to be loose. Don't look for a problem where there isn't one.

 

Did you compare the new pushrod length to the old, were they exactly the same?

 

It's hard to tell but they look the same. The replacements I got are Mehling MPR-307, they're supposed to be direct fit stock replacements for small block Oldsmobile V8s.

 

Thank you, this is good to know I didn't mess anything up. The engine was primed before putting it back in but it hasn't been started in quite a while.