RomulanS13

I've got to the point of being able to start my dual cam and when i do try and start it back fired the first few times so I re did the timing at dizzy. It has spark I replaced the fuel pump cause the old one seized from sitting so long and I drained and cleaned the tank out had a lot of white sediment in the tank.

Now when i try and start it will turn over 3 or 4 times and completely stop with a thud sound seems like the motor seizes. Ill re crank and it will do the same thing but this time no back fire but there is a loud hissing after a few cranks.

The previous owner deleted all emissions maybe the vacuum routing is wrong?