First off, valvetrain mods include Blox dual valve springs with Supertech aluminum retainers on stock valves with 12k on re-lap and AEM tru-time cam gears. I left a red light light and didn't make it more than 50 feet before my teg started shaking like it had a TERRIBLE miss then died. I tried to start it again after checking fuel pump/filter, plug wires etc. and it would turn over but not start. After a few tries I felt the engine stop suddenly so I towed it home to find 2 of my retainers (#3 intake, #2 exhaust) pressed down into the valve springs by the rockers. The valves had come loose and dropped, hence the engine siezing up. I very carefully rotated the engine by hand to check timing marks and everything appears to be copacetic. What could have caused this? especially 2 at a time and on different cylinders/camshafts? I'm relatively experienced and at the moment I'm perplexed. Any input would be appreciated.

 

-Valve Keepers might not have been installed correctly, weren't fully seated.
-Retainer wasnt completely compatible with Stock OEM valves or Blox Valve Spring Rate and somehow failed?

We dont even know on what engine you're talking about.
Who did all the engine assembly work?

 

It's a B18c1 and all machine and assembly work was done by a valve train tech at a local performance engine builder. It ran for almost 13,000 miles without a problem is why I think the keepers were ok. I'm forced to believe it was indeed a compatibility issue. By the way one of the #2 exhaust valves broke and fell into the c.c. destroying the forged piston and head.