What can be some of the causes for new roller lifters to brake with less than 30 mins. running time?

There can be many reasons. A few that come to mind are...

incorrect spring pressure
oiling problems
misadjusted lash
faulty lifter
tight lifter bore
lifter bore misalignment
cam walk
defective cam core

Thanks Vinny, We had about the same list.

HP,
How about some additional details ? Was this a set of replacement lifters with nothing else being done to the engine ? Big Block or Small Block ? What actually "broke" ?

Bill Koustenis
Advanved Automotive Machine
Waldorf MD

New rebuild, big block 540 ci. dart block and pro 1 dart heads.
New Crower lifters. reused old cam, new valve train.
#6 lifter broke after about 30 mins running time. The rail that connects the lifters is what broke and this allowed the lifter to turn sideways on the cam

Ouch

Almost hate to ask, but any chance the lifters were not in correct ? I have seen guys put them in with the bar upside down and it will run but cause a major mess. I cannot think of anything in the valve train that would cause the link bar to break. Were they the correct lifters (tall ones) if needed ?

Bill Koustenis
Advanced Automotive Machine
Waldorf Md

That was the first thing we thought before pulling it down, but I'm sure they were installed correctly, but as you know there is not way to tell for sure now. At least all the other lifters do have the arrow pointing up, and yes we run the tall lifters.

pushrod flexing

You should be able to tell unless both lifters came all the way out of the bores.

That was another question also, when you did the tall lifters did you change the pushrod lengths? Maybe you hung a valve. Did any pushrods break? Remove the head and see if the piston and the valve met.