1990 grand wagoneer wierd popping noise

[thechief86]

hey guys, i tried to ask about this on the full size jeep forum, and nobody has said anything yet...
what i'm dealing with is a motor that i swapped in that i got for free after it sat uncovered in a parking lot at a shop near the beach for several months. it is the AMC 360 v8 out of a 1983 cherokee laredo. it runs pretty decent, save for a few exhaust leaks i need to work out, and i get this strange popping noise that from the inside of the jeep sounds a lot like the rod knock that my old motor had, but it's intermittent, and doesn't coincide with engine rpm's, but it does seem to make the engine shut off for half a second when it pops... i pulled the air cleaner off for easier access to the carb screws, and with the motor running and the air cleaner off, it is obvious that the popping sound is coming from inside the stock motorcraft 2150 2bbl carb. the carb is relatively fresh remanufactured from vato zone, with only 3,000 or so miles on it... do you guys know what i can do to get rid of the popping noise? i had no problems with this until i swapped in the free motor.:helpme:

next day: i plugged all the vacuum stuff, and still have the pop. added lucas fuel treatment, still popping. motor runs good, aside from this.

anybody know what's up?

 

[winterbeater]

Is it popping out of the carb like an intake valve sticking? Then the combustion goes up past the intake valve.

 

[Shorty]

sounds like a winner to me. Valve sticks/ doesn't seat and the resulting lack of compression will feel like a dead spot at idle each time it does it.

 

[8Mud]

Firing order 1-8-4-3-6-5-7-2. Cylinder number one is front *left* as you are sitting in the drivers seat, odd numbers on the left, even on the right. Number one on the distributor cap faces front 12 O'clock. Firing order is clockwise on the cap.
Static time by turning engine over until pressure blows your thumb off of number one spark plug hole (or better yet use a compression tester). Line the timing mark up to 8 degrees and turn the *distributor* until you get a spark to number one cable, then tighten the hold down bolt for the distributor. In fact you can use anything between about 8 degrees and 2 degrees, it will be fine. Later you can fine tune it.
Ohm the coil and spark plug cables. Disconnect the condenser inside the distributor if it has one (and throw it away).
Do a compression test, then a vacuum test. If you have a bad valve the needle will swing with the bad valve (fairly radically) on a vacuum tester with the motor running. Compression will be low on the cylinder with a bad valve.
Carburetors are subject to gunk up, especially the float vale and the choke. No big deal to clean out, the carb gasket often breaks though when you clean the float valve and the float tub.
Could be a number of things, if you have a bad cable sometimes the spark can jump to an adjacent cable and fire at the wrong time. If the timing is off significantly, it may also crossfire. Wipe out the inside of the distributor cap.
I usually spray some penetrating oil into every spark plug hole ( a couple of seconds worth), clean off the plugs with a wire brush and gap them and spray some oil down the carb (about 8-10 seconds worth). Check inside the carb and as far as you can see down the intake for mice or whatever, the same with the exhaust.
If your vacuum advance is acting up, it may pop some as the RPM's increase. Check the springs on the weights in the distributor. A little spray oil onto the advance mechanism isn't going to hurt anything, just don't overdo it.

These are the first steps in firing up a new to you motor.

 

[jneary]

the power valves on the carb leak, but i think it would make it run rich and not so much popping. if it is popping trough the carb, i would recheck the firing order or possibly a sticking valve. you may also have a loose or bad plug wire or a misgapped plug