Hi i have a 305 with 350 vortec heads, lt1 cam and 650 carb. Car has been driving fine for the past few months but i have had a slight oil leak coming from the rear intake manifold seal, So i pulled the intake and replaced all seals. When i re installed everything i can get my motor to crank but not fire...I checked spark, fuel, air and my timing is lined up with the #1 cylinder. I also place my thumb over the #1 hole and when i get compression its pointing at the #1 cylinder. I get exhaust backfires when cranking sometimes also. I build oil pressure also. Any thoughts?

 

yup

you stabbed the distributor 180 degrees off. Your TDC you feel is exhaust.

reverse the wires 180 degrees and see if it fires. When it does, you can then decide if it's worth it to re-stab the dist or just mark the cap with the correct wire #s