Insane Valve Issue

[chevylookin]

Hello all,
I just replaced the spark plugs and changed the oil on my '89 Carb'd Chevy 350. I replaced the conventional plugs with platinum types. On my last oil change (about 2000 miles or so ago) I ran a quart of Marvel in with the oil as the engine is getting up there in the unknown mileage. I did a slight timing and carb adjustment and everything was running great! I jumped in her, and took her around the block (73 Blazer). Within half a mile, I started getting vale train noise and by the time I got home, it sounded like a hail storm. Thinking it could be a loose plug that didnt go in all the way I started checking. Found one loose one as they are hard to confirm "all the way in and tight" with the headers in the way. Tighten it up. Same thing. Started to remove the new plugs and found half of them had changed their gaps because the electrode tabs are too thin. Replaced with old plugs. Same thing. Removed the valve covers and I can literally push almost all of the rods down 1/8"-1/4" into the lifters at the rocker. I am sure this isnt normal. But how could I have collapsed so many lifters so quickly? Could it be I spun some bearings? Oh Christ please no!
Thanks, Ryan
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