another wont starte thread. sorry

i turn the key on my 67 valiant 318 and it turns over nice and fast but wont start. and when i turn key off then on it will throw a fire ball out the exhaust. so im getting fuel and spark. what would make it not start but do that?

I would not assume it's getting spark

You must understand that the ignition power comes from two sources, and they do not "overlap"

When in "run" known by Mopar (diagrams) as "IGN1" power comes from the traditional dark blue wire, from the switch, through the bulkhead, to the ignition, regulator, alternator field and on some cars a few other things like electric choke if used

BUT IN START all that "run" buss goes COLD. NO power to it in "start"

In "start" rather there is a separate contact in the ign switch which supplies ignition power through the traditional brown wire known as "IGN2" out through the bulkhead, and to the coil+ side of the ballast resistor.

THIS CIRCUIT may be dead, and not providing "start" spark. You may be "cranking in" a whole bunch of fuel, and when you snap the key back to "run" you DO get a spark, which blows up the mixture.

SO.....................

very first thing to do is to rig a test gap (spare plug) to the coil, where you can see it under the hood, such as up on the cowling lip, and crank the engine USING THE KEY to check for a starting spark.

how do i rig a test gap?

If you can locate the connecotor on the ballast resistor with the brown wire,
and if you have a 12 V test lamp...
Pull that connector off and attach your test lamp. Prop it in a manner where you can see it from the ignition switch. If the lamp comes on when the switch is in start position, the circuit is good, the switch is good. Ballast resistor is bad.
To run the engine for a long period without a ballast resistor can overheat the coil but...
If the part store is close to you, you can install a jumper attaching all the wires on the ballast resistor a drive it.

Mine did the same thing. Ended up be the ground wire under the dash. Mine only sparked when you turn off. Good luck.

i looked under the dash and the ground that goes to the steering column wasnt gounded.