engine pops out the carb and kills it

[Justin Tawney]

so when the engine revs up or randomly it pops out of the carb sometimes shoots flames and kills it. the idle is close to right and the timing chain was just adjusted and timed as close as I could get by ear. would that be a bad valve? I am juyst tring to get it home about 5 to 10 minute drive away so I can work on it at my house. is there any way I could keep it running enough to get it home? please help

[LeviGideon]

Check if your points are gapped. If they aren't opening you've found your problem.

[Justin Tawney]

whats the gap supposed to be? 18?

[EricJB]

Check your plug wires. The firing order is 1342 and the dist spins counter clockwise. Find 1 and work your way around.

[Justin Tawney]

firing order is right too. I have checked almost everything. only thing I can think of is a bad valve..

[Justin Tawney]

wish I had it here so I could take a video of what its doing to show.

[EricJB]

Pull the valve cover and take a look at the rockers. Roll it over and make sure valves are opening and closing. Stuck valve, rocker come off, or flat cam.

[datzenmike]

Backfire through carb...

 

Spark jumping to wrong cylinder. (rotor or cap carbon tracked, bad wires)

 

Intake valve too tight and not closing properly. (adjust)

Intake valve burnt or bent or otherwise not closing properly. (replace or rebuild head)

 

Exhaust valve not opening, rocker arm fell off. (put back on)

 

Carb goes suddenly lean. (float set to high, jet plugged, fuel filter dirty)

 

 

 

Check and set valve lash.

[jesusno2]

Timing chain was just adjusted? You sure your cam timing is right? Distribitor oil pump alignment correct? Backfiring through the carb is normally a timing problem, or a really lean carb, but since you mentioned "timing chain" i would think that is where your problem is.

[EricJB]

I would call a lean carb more of a spit than a pop with flames. But it usually stops the motor as well. Timing it by ear. probably not close enough. If it still has points you can use an ohmmeter or a test light. hook it up to the points (disconnect it from the condenser) and slowly turn the motor by hand. When the points break open and the opens the circuit, look at the pulley. Adjust, repeat. That is how you do an old dirt bike, or an aircooled VW when your poor. I have made them with a dome light bulb ( torpedo style) and some wire. As stated above, recheck cam timing and valvetrain.

[Justin Tawney]

I set the timing chain exactly what the book says. found tdc lined up the cam shaft put the colored links on the right spots. its all correct. and at tdc the rotor points to number 1 spark plug wire which is to the left when looking at the engine getting spark to all 4 plugs readjusted the idle on the carb a few times trying to find the right setting to keep it running. and when it pops sometimes it pops a few times or once and dies right away starts buck up but will poop again.

[datsunaholic]

Really worn out distributors will do this too- the shaft wobble makes it fire somewhat randomly.

[banzai510(hainz)]

Justin your the Man . Timming chain sounds right.

ck the valve lash on the rockers IF you open the valve cover.

But I would ck the dizzy like Datsunaholic says for points or possible condensor(if still running points). Or adding a MSD coil or Supercoil or a later EI coil or removing th ballast resisitor could do this also while still running points. If those are still stock ck for dizzy wear . the shaft will wiggle as Datsaholic said.

then look at carb.  try run with choke see if runs better.  if runs better then you know your ignition is fine.

[Justin Tawney]

I bypassed the ballast resistor because it was bad. if I get a new one what side of what wire connects to it. I don't remember and could that be the problem if the resistor is not there?

[Justin Tawney]

ill buy a new ballast resistor and see if that works. and what exactly does that do? give it stronger spark or what?

[datsunaholic]

Ballast resistor keeps from burning up the points and points-type low resistance coils.  They don't last long without one.

[Justin Tawney]

got one put it in still same problem.

[Justin Tawney]

and is it normal for the rotor to be able to turn a little bit by hand or does that mean the distributer is bad. and the valves are all opening all the way normally when I turn it over with the valve cover off. could that mean a valve or head is bad?

[datzenmike]

Opening all the way isn't the problem. It's that they have to close fully and tightly to contain the fuel/air explosion. It any leak out it will light off the fuel and air in the intake and explode out the carb.

 

 

Backfire through carb...

 

Spark jumping to wrong cylinder. (rotor or cap carbon tracked, bad wires)

 

Intake valve too tight and not closing properly. (adjust)

Intake valve burnt or bent or otherwise not closing properly. (replace or rebuild head)

 

Exhaust valve not opening, rocker arm fell off. (put back on)

 

Carb goes suddenly lean. (float set to high, jet plugged, fuel filter dirty)

 

 

 

Check and set valve lash.

 

  Check the valve lash. The clearance between the valve and the rocker or cam follower. If no clearance, maybe the valve is not closed all the way.

[Justin Tawney]

valve lash is good

[datzenmike]

I had to go check some of your other posts to get all the info. You rebuilt the carb and one of my possible causes of a backfire is running lean.

 

Primary jet has dirt in it blocking the flow.

 

Carb loose or gasket leaking vacuum.

 

Fuel filter plugged or float set too low.

[Justin Tawney]

was working on it today and cant get to start. it will start barely idle then when I give it gas it kills it.

[datzenmike]

Yes. I know that.

 

 

This is how it usually works. You describe a problem, but I'm not there and don't see what you see, so I ask questions. Did you try this... have you tried that. You try it and get back to me. Slowly but surely the problem is isolated and can be fixed. There are so many different thinks that can cause this we have to eliminate them sometimes one by one. Skipping over one is no good. We could go on for days only to come back to it.

 

 

Seems to me you asked for help with a distributor and I offered suggestions to try that were ignored and it was a waste of time.

 

 

 

So,..... did you look at the carb?

 

 

I had to go check some of your other posts to get all the info. You rebuilt the carb and one of my possible causes of a backfire is running lean.

Primary jet has dirt in it blocking the flow.

Carb loose or gasket leaking vacuum.

Fuel filter plugged or float set too low.

[Justin Tawney]

floats fine filters not clogged I could try ti tighten the carb downa little more. but I had it running sort of. and got it to my buddies house. put in new gas runs better but I cant get it running enough to drive.

[Justin Tawney]

ok so it runs I can drive it down the street and around the block blinkers don't work so didn't drive it far and now the oil looks like chocolate milk :( that means I need a new head gasket right? and ive been trying to get some of the bondo off so I can get to the few rust spots im going to cut a chunk off the left side of the bed and weld a piece of sheet metal. and the front end between the two blinker lights is all messed up. been trying to pull that out and make it straight again.