I have a 96 Chevy short bed 4 wheel drive that had a blown motor (4.3 v6) I put another motor in. Problem is that I have no fire at the plugs. I have put a new timing chain,coil,distributor,plugs,...

You may need to reprogram your ECM to the new motor...

How do I do that and why ? I only ask y because they are the same motors.

The same motors & same sensors whether new or not, you should be able to start it. So you are not getting spark? Need to check connections at the coil and make sure it is getting 12V to energize it. Now I believe the 12V is controlled by the ignition control module, These can be tested at Auto Zone.

Also the coil can be tested by a resistance check. It must fall into certain parameters that can be checked. I don't know what the resistance should be, or sequence of check, but that can be found out. Again Auto Zone should be able to help on this.

Both of them are new

Well still something is not allowing the coil to energize, check for the 12V. New distributor you say? As in brand new? Did you check for spark out of the coil itself?

Yes the hole distributor is new so is coil and mod as well

Did you check for spark off of the coil wire itself?

And I got 11.15V to the coil but it's kinda cold n my garage

That is fine, coil should be energized, so something is not letting the spark release to the plugs. How are the cap, rotor, & wires?

All of them are brand new

See, I thought of the security system but if it were on, on that one you would still have spark as it shuts down power to the injectors. So it is something that is not allowing the coil to send its spark. The ignition control module is what makes or breaks the circuit for the coil to deliver its spark. That or the pick-up coil, I will Ask again, did you check for spark at the coil wire?

Ok, I remember now running into this... that distributor must be stuck exactly in the right location, even a tooth off and it will not fire. May have to check that again.

Thinking about this more, when you are set at TDC on the compression stroke, your rotor is not pointing at #1 spark plug wire as the distributor cap is designed as a low profile cap. # 1 terminal under the cap is more in a 7 to 8 o clock position. If this is not wright, you will not develop a spark.

That's about where it's at but I put a new timing chain and gears in . If I wasn't dead nuts top center when I slid those gears on would that throw it out.

I know it was real close but sometimes working alone shit happen

Just wondering but that new distributor had a mark in the 7 to 8 o'clock position and it lined up on it but? ? ? ? ?

Yes, I know, and there is no way to have the gears on wrong if they only have the one key way and the one timing mark. You should have ben able to just turn the crank so the mark on the gear is at 12 o clock, and the camshaft gear mark at 6 o clock. I like rotating it around 2 revolutions after getting the chain back on to make sure the marks line back up dead nuts. But when doing this you want to have the cylinders lubricated, with the spark plugs out for ease of rotation. I think your distributor is not in wright, you can't adjust that one, needs to be in dead nuts also. If you are to work on this today I will monitor my computer threw the day.

There are actually two marks on the shaft to line up, this is for ease of dropping it in as the rotor turns slightly clockwise as it is seated in. Sometimes you have to get in there to line up the oil pump shaft if the distributor does not seat . Just don't drop the tool down into the motor. Another thing is I looked on u-tube on this and found a video on how to do this. Should look it up, it is very helpful.