just did a fresh rebuild on a 2003 5.7, bought trunk with eng knock, spun #8 bearing, block was boiled and bored .030 over, crank was turned and rods reconditioned. heads completely reconditioned, new seats, guides and seals. took shop weeks too long. timin
g was double checked on assembly. bearings plastic gauged to check gap.
was not easy to start with I purchased it, thinking injectors might be dirty (168K miles). have to hold gas at least 1/2 throttle to get it to start, will run for a few seconds and just cuts off as if key was shut off. no sputter no miss, just dies. oil pressure good(dead center gauge), alt gauge swings way to right showing full charge. once it got oil through the system all knocks and click went away. runs very well and quite for the 10-45 seconds it will run.

Any ideas?

 

Check Fuel pressures?

 

I Agree..

 

Sounds like either a vacuum leak or something didn't get hooked back up when the engine was reinstalled.