[68 TT]

Squirt a little oil into each cylinder and crank it over with the ignition disconnected to spread it around then reconnect the ignition. Sometimes new engines don't like to fire on dry cylinder walls. The rings aren't seated yet and leak down too much on the dry fit to build enough compression to fire the mixture.

The 400 in my Malibu was that way. I didn't believe it was the problem and pulled most of my hair out trying to get it to run until my 82 year old neighbor suggested the oil in the cylinder trick. It fired right up.