Cam bearing failure

I have a new 521 (boat engine) that I had a local shop do all the machine work and build the short block. I put in the cam and installed the heads. Did break in and everything seemed good, 80 psi oil pressure, changed oil after first 30 min of running on trailer. I took it out to a local lake and everything seemed fine for about 5 min of total run time but started to hear what I thought was a loose lifter so put it back on the trailer still making 65lbs oil pressure. Well today I pulled the valve covers and every rocker except the front two were loose, so I instantly thought I lost the cam (hyd roller). Took intake and front cover off and found that every cam bearing except the front one was GONE (as in not a piece left in the bore) and the front one was thrashed. My question is what could cause this? Have maybe a total of 35 minutes of run time and never lost oil pressure, was 80lbs off idle and 65 at hot idle. The local shop also installed the cam bearings. Is this something I did or didn't do? Trying to figure out how the rear 4 bearings could literally be gone and I know there were in there when I installed the camshaft. I have yet to take the engine out of the boat so I'm unaware as to the condition of the rods and mains yet.

Were the oil holes in the cam bearings all lined up properly with the block? Never heard of anything like this...

What cam bearings ? Isn't that why we use Durabond bearings with roller cams ? Normal bearings can stick or pickup??? I thought then they normally spin in the block ?

Surprising to do that damage so fast

All the oil holes were lined up and I was using king HP cam bearings as well.

Cam bearings did'nt have sufficient 'crush' to stay tight in the cam bores? Cam with spring pressure against it caused the bearings to spin and walk out of their bores....just thinking about it.

When you find out the cause of the bearing failure please let us know. I've never heard of this kind of failure before.

My guess is their was only one cam bearing installed to start with. You most likely just overlooked the rest because the front was tight. Cam bearings do not simply disappear from a block.
Unless they were fit very loose and you knocked them out putting the cam in. Surely you would’ve heard them bouncing around if that happened.

Cut your oil filter open & let us know what you find, hard to imagine leaving cam bearings out during assembly but I guess stranger things have happened before. I

I like the others the bearings was never installed if they did slide out you should be able to see evidence of the bearings on the cam and lobes. Cam bearings are 1 peace so the lifters would have had to go chew it up and you would see the evidence on the lobe and lifters if they was put in

Well all cam bearings were installed as the remnants of them were in the oil pan. The cam tunnel is totally jacked and if I had to make a guess I would say that there was not enough cam/bearing clearance and it spun them until they got destroyed and fell to the bottom. Hopefully they can save the block and bore the cam tunnel for roller bearings.