Rebuilt engine it ran for about five minutes backfired and shut off

Hello and thank you for using 2CarPros. Here is a link to troubleshoot this. Just follow it and we can narrow this down and got it fix for you.

https://www.2carpros.com/articles/car-cranks-but-wont-start

If you have any questions or need help let me know.

Rich.

On a side note. Backfiring is caused from a lean fuel mixture. I am not sure which carburetor you have on that, I believe a Holley was stock on those, but a backfire will blow out the power valve in those which in turn causes a lean mixture. You can also check for a weak fuel pump (flow and or pressure) and a plugged fuel filter. Also confirm your timing is set right.

Let us know what you find out.

Thanks, Rich.

I am so sorry. Sadly people like that are everywhere. He has left you with quite a mess.

I am more than happy to walk you through this step by step. Is this something you can or want to tackle? The good news is due to the age of the vehicle everything will be fairly simple but there will be a good bit of testing and we have several issues it sounds like.

Also the open vacuum port you mentioned can cause the backfiring.

Rich.

Okay then lets get his thing running.

Lets make sure we have not only spark, but good spark. I need you to pull all the spark plugs. Keep them in order as you pull them so you know which one came from each cylinder. Once you have done that I need you to look at each of them and note what color the porcelain is on each plug. Take notes so you can tell me if they are all the same color, If some or even one is a different color take a close up picture of it and tell me which cylinder it came from. A normal plug should be tan to medium brown.

Once you have that done, plug one of the spark plugs into a plug wire and hold the threads on the plug to the engine block and crank it over with the key. (This will take 2 people) I suggest your wife hold the plug and you crank the motor because I need you to tell me if you have spark at the plug and what color the spark is. Is it blue, yellow, orange or white?

Also I would hold the spark plug with a pair of pliers that have a rubber handle in case your wires are leaking voltage and you wont get zapped using pliers to hold it.

Let me know what you find and we will move on. If you have any trouble let me know and we can straighten it out.

Rich.

Good work. Can you please shoot a quick video with your phone of the engine cranking over so we can see what's going on? That would be great. You can upload it here with your response. I will be able to tell if the engine is okay from the video.

That rod runs your distributor and the oil pump so it is critical it goes back in correctly.

First you need to set the motor to top dead center on the compression stroke on the #1 cylinder. The easiest way to do this is to pull the #1 spark plug. Put your finger over the plug hole. Not in the hole but over it. Then crank to motor until you feel the pressure blow your finger off the hole. Then put a ratchet on the crank bolt that holds the harmonic balancer on and line up the notch on the balancer with the TDC mark on the timing chain cover. That will be TDC top dead center.

Then put the rod back in the hole. Note:
Both ends of the rod should be keyed. Make sure the end that was down goes back in down and engages the oil pump.

Now comes the fun part. The distributor is run by the end of the cam shaft. You will notice the worm gear on the end of the distributor. As you drop the distributor back in the hole the rotor will turn as the worm gear engages. Here is what needs to happen all at once. The slot in the rod has to line up with the slot in the bottom of the distributor shaft when the distributor drops all the way down you need the rotor pointing at the #8 spark plug so that it is pointing at #1 on the distributor cap. See image below.

In order to do this you need to line up the rod with the slot on the bottom of the distributor shaft and because it will turn as you put it in you need the rotor pointing at the #4 cylinder so that as it rotates on the way in it ends up pointing at #8 when its all the way down.

You will find you will need to turn that rod just a bit again and again until it lines up.

If this is not put in correctly, the car will not run.

Also note.. when the distributor is installed the shoulder at the bottom of it should be all the way down to the motor with no gap. If you have a gap it is not all the way down and is probably hanging up on the rod.

Here is a video to help you get an idea of what to do:

https://youtu.be/mZ17tftzkeo

Once you get this back in let me know and we can set the timing.

Let me know how it goes, Rich