There is 85,000 miles on the engine. The starter spins the engine fine, but, it sounds like there is no spark. This happens when the air temp is warm, but the car does start when the air temp is cool. My regular mechanic can not find anything wrong.
Make sure there is a good spark to all plugs.
Fuel supply? Ensure the fuel pump is working. Do you hear it priming when you turn the key on?
When was the last complete service (‘tune up’) done and what was done?
The engine was a replacement a couple of months ago. Whatever service was typically done was done then.
You can hear the pump.
It has been to two different garages. It has never not started once it was towed there.
My area was not heavy line but my stall was next to the heavy line area. When these guys finished an intake on a 3.4 (your engine) many required excessive cranking to get a inital start,after that all was well. Never quite figured it out.
I would concentrate on an assemply error (perhaps hydraulic lash is non-existant) or more likely a fuel pressure bleed down situation.
Let us know the extent of the “rebuild” or replacement. Did the mechanic have to put on heads and manifold himself? plenty of room for error there.