Help With my crate 427 Engine Won't Start

[bobcowan]

If it is backfiring through the intake, then it is firing while the intake valve is open.

Most likely, you need to re-adjust the valve lash.

Before the engine is run, it's really difficult to find zero lash, because the lifters are not really full of oil yet. It's really common to get them too tight at first, which holds them open when it builds oil pressure.

Go around all the valves and loosen them about 1/3 turn. Then see if it starts.

When you get it running, you'll need to go around and do it again, so it's perfect. To find zero lash, tighten the nuts to just finger tight. You'll feel it when you hit zero.