Okay, here we go, I went and got gas the other day. When I went to restart the car...nothing. I knew I needed a new starter and batter, so I replaced them. Now, when I go to start the car it starts up for a second and backfires through the carb. I had to try several times to get it to do that. I have an MSd ignition hei with 6al. Any thoughts on this?

hmmm maybe too much initial advance on the timing.

Slipped timing chain perhaps? How fresh is the motor? Do you know what kind of timing chain / gear setup you have?

ya id agree with the timing being off
my friends distributor wasnt tight enough and it slipped when he stepped into. when the dist slipped there was a huge earth shattering backfire and the car wouldnt start

i agree too timing is off may have jumped a tooth. Kenny

before we get too carried away with internals.... a backfire is normally caused by RETARDED timing. Mark on the distributor body where the #1 wire position on the cap is.... don't assume, actually follow the wire back from the #1 plug. Take off the distributor cap. If the distributor has been out of the engine since the last time it ran, pull the #1 plug, too. bump the starter until the timing mark on the balancer is lined up with the timing tab (if the distributor has been out, put your finger in the #1 plug hole and feel for pressure when you do this.) If the rotor is pointing far away from your mark, spin it 1 more complete turn. (unless you felt pressure in #1, if you did, the distributor is probably 180 out. This is not likely if the distributor has not been out of the engine since the last time it ran right.)

Once the engine is on #1 compression for sure, and the rotor is pointing in the general direction of your #1 wire mark, turn the engine so the balancer mark is aligned with 8 - 12 degrees advanced on the timing tab. Then loosen the distributor and turn the distributor so the rotor points exactly at your mark. Put the cap back on, make sure all the wires are tight, #1 plug back in, and verify the correct wiring (1 8 4 3 6 5 7 2 counterclockwise around the distributor cap.

Snug the distributor clamp, tight enuf to hold it but loose enuf so you can still turn it if u try.

Have someone else turn the key.

If it sounds like the starter is working too hard, push the vac can toward the firewall to retard the timing.

If it sounds like it's spinning free, or it backfires, pull the vac can toward the carb.

See if it starts!

jim, he said it was running and he went to get gas, im betting on jumped chain.Kenny

Ok, today I finally got some time to work on the car....I advanced the distributor.....alot. The car run great now. I bet I moved it 1/2 to 3/4 of an inch. I am more of a driver then a mechanic, but I am learning as I go. What would cause this. I could see a little bit, but jeez...

If the distributor is not tight it will back itself off and retard the timing. I have seen this happen many times. Make sure it is tight after you set the timing.