im stumped

[87MonteSS]

You might be on to something with the valve lash.

Make sure each cylinder is at TDC on the compression stroke, loosen the nut until the rocker is loose, slowly tighten the nut while spinning the push rod, when the push rod has some resistance to turning tighten the nut another 3/4 turn.

 

[bigdan]

let's assume the valve lash is okay....

turn over your engine until you get the no 1 piston at TDC (compression)((will build pressure true spark plug hole ...)
lift the dist cap ,look at the rotor, where it's pointing .....
if on NO1 cyl wire ...just give it more advance (turn counterclockwise)

a backfire is a sign of not enough advance if all else is ok

Dan

 

[Silent viewer]

I would be willing to bet the distributer is 180 degrees off. i have had the same issue and it would run but very very badly.

 

[bigdan]

it would run at 180 deg off ...... :shock:

you're a lucky man! never could get one to run like that ! 😳
Dan

 

[megaladon6]

yeah, i've made that mistake twice! it would feel like it would start, but not happening.