AMC 360 help

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ducter

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Hey guys, know this isn't a Mopar topic but hoping to get some help.

Been working on getting my new to me 1980 Cherokee running, I replaced the carburetor yesterday as the Holley that was on it had been sitting since 1991, thought it easier to just replace. Put on an edelbrock 4105.

Same thing is happening as with the Holley, it's not starting but popping from the carb. I actually tracked down the owner that parked it back in 91, he said it drove fine then starting popping from the carburetor and wouldn't start. He had about 30 vehicles he was collecting and just parked it in a garage where it sat, sold it to the guy I got it from last year and he hadn't done anything with it either.

It's got clean fresh gas, new carburetor, I have triple checked the plug wires and am starting to think timing. When I put gas in the carb it will fire for a second then pops and won't fire again till the motor turns over a few more times, then same thing again.

What's the best procedure to check timing on a motor that won't run? Pull #1 plug, put finger over hole and turn over by hand until I feel the pressure building under my finger, insert a wood dowel into the hole and turn till it's at the highest point? That would be the top of the compression stroke, rotor should be pointed at #1 plug on cap and harmonic balancer should read 0 correct?

Or if anyone has any different ideas as to what it could be I am all ears.

Thanks for any help, I posted this same question on a fsj forum but figured I know some intelligent guys that know way more then I hang out here so figured why not..
 
Could be valve stuck open for some reason, or exhaust valve SHUT (flat cam, something broken)

Using a dowel only tells you the piston is "somewhere up." It's not accurate and does NOT tell you compression stroke

There are only two (three) ways to figure compression stroke assuming timing mark is accurate

1....finger in the hole feel for compression, then look for marks

2...Pull VC and look at valves. No 1 valves both closed on compression stroke

3...Pull dist and "guess" turning it half turn 1 and 2 are the recommended LOL
 
Could be valve stuck open for some reason, or exhaust valve SHUT (flat cam, something broken)

Using a dowel only tells you the piston is "somewhere up." It's not accurate and does NOT tell you compression stroke

There are only two (three) ways to figure compression stroke assuming timing mark is accurate

1....finger in the hole feel for compression, then look for marks

2...Pull VC and look at valves. No 1 valves both closed on compression stroke

3...Pull dist and "guess" turning it half turn 1 and 2 are the recommended LOL

Alright thanks. I assumed that when I started to feel force under my finger, insert dowel and continue turning by hand till it was at its highest would be the top of the compression stroke. Maybe I'll just pull the vc so I can be certain.

I honestly don't know where to start in trying to figure out what's wrong with it but I simply can't afford to take it somewhere so trying on my own is my only hope.
 
You can easily work through this if you have basic mechanics skills

If I came across an unknown engine and ran into something that didn't "jive" I'd probably do this

1....Us a piston stop and confirm the timing marks are accurate (slipped balancer, etc)

2.....Check the timing, and "hope" that it seemed set up IE 'had run' previously. Also check for spark "quality" IE "enough" and hot spark.

If that looks OK and it won't run........

3....Run a compression check. This also gives you an opportunity to check the plugs CHECK THE PLUG WIRES for electrical continuity and take a GOOD look at cap / rotor for damage / dirt/ moisture

4....Consider pulling the VC and examing the valve gear for damage, or stuck valves

5....If the timing appears off, and it seems likely it "had run" immediately suspect a slipped timing chain. If you can estimate the cam specs, you can check this easily on a intake closing event, because it's close to TDC and you can estimate closing degrees

6...Otherwise, go through the "finger in the hole," set up timing so you KNOW it's OK, and go from there

"The usual" throw a little fresh gas down the carb and suspect bad fuel.
 
Do not use a wooden dowel. If it breaks, how in the world will you get it out of there?

It really sounds like an exhaust valve problem.
If it was mine, I'd perform a leak-down test. If you dont have a tester, you might try a compression test. Not nearly as accurate, but it should pin-point the bad cylinder;at least.

Valves like to stick in the guides when left sitting for long periods of time. Sometimes the piston gives it (a stuck-open one) a smack on its way by. Of course then it's tear-down time.
 
Backfire from the carb is stuck valve, timing is way off or timing chain has slipped.
 
Run a compression test.
 
Thank you guys, if I have time after work I am going to check the timing. I'll follow up with what I find. Thank you all for taking the time to respond.
 
I know how to check the timing but how would I know if the timing chain jumped or check for stuck valves? If the timing chain jump a tooth, would it show up just checking for timing and not being able to get it set? For a stuck valve do I just pull the valve cover and look for a stuck valve?
 
Timing chain - remove distributor cap, turn engine clockwise until the TDC mark is at "0" on the timing cover. Then while watching THE ROTOR - very slowly turn the engine counterclockwise just until you see the rort start to move. Then look back at the balancer mark for how many degrees the crank moved before the rotor moved. More than 2-3 degrees is a slopy chain and potential slippage.
Valves (and to some extent chain slippage) - compression readings. If one hole is really low or non-existent and the compression leaks up out the carb - there's your problem. If the compression readings are just really low, the chain probably jumped.
 
............how would I know if the timing chain jumped or check for stuck valves? If the timing chain jump a tooth, would it show up just checking for timing and not being able to get it set? For a stuck valve do I just pull the valve cover and look for a stuck valve?

Timing chain - remove distributor cap, turn engine clockwise until the TDC mark is at "0" on the timing cover. Then while watching THE ROTOR - very slowly turn the engine counterclockwise just until you see the rort start to move. Then look back at the balancer mark for how many degrees the crank moved before the rotor moved. More than 2-3 degrees is a slopy chain and potential slippage.
Valves (and to some extent chain slippage) - compression readings. If one hole is really low or non-existent and the compression leaks up out the carb - there's your problem. If the compression readings are just really low, the chain probably jumped.

We've already answered some of this. Compression test, leakdown test, or pull the valve covers

Another way to estimate timing chain problems is outlined in the Mopar service manuals which you can download over at MyMopar. In the engine section, there's a way to estimate valve timing events. I already mentioned this. Use the intake closing event, as it happens near TDC and you can estimate the timing. However you HAVE to know what you have for a cam, IE factory, or aftermarket, and what the cam timing is.

You can only find out by checking ignition timing IF the timing has not been messed with. I also already addressed this above. IF the engine had run, and the timing HAS NOT been messed with, then if it shows out of time, then the cam is slipped.

Sounds to me you need to start at the top of this thread and re-read it. There has been some very good info given here, and now we are starting to repeat it.
 
good advise.
Personally, I'd use a compression gage to get #1 on the compression stroke. Then you can also use it to check for compression.

Yes at TDC on compression the mark on the balancer should line up with 0.
Beware on the AMC 360, A = Advanced. So the 10 mark is 10 deg advanced, aka 10 BTDC.
10-12 deg at 600rpm is typical for FSJ factory initial timing.
As good starting point for initial timing as any.
 
Doing a compression test, I got right around 120 on 1,3,5,7 swapped to the other side and #2 reads 30. Will try it wet and see what it reads but not looking good at all.

Edit-45 wet. Guess I shouldn't have trusted the guy I got it from when he said it runs with some gas poured into it. I am an honest person and some reason I expect others to be the same. Lesson learned.
 
Sorry for your loss.............
Now, all is not yet lost.
Theres a good chance that one or both valves in #2 are bent. But its not a for-sure thing.It needs to be proven, cause there is a slim chance that one is just not seating,due to varnish on the stem.

This is what I would do;
I would put #2 (passenger front) at TDC compression. I would pull the valve cover off. I would check the positions of the valves and the valve lash. If there is a sloppy loose arm, thats the problem valve.
So what we need to find out is if its bent or just stuck near closed. If the lash is more than about .150 down, its probably bent.If the lash is just about .150 or less, then it may just be stuck.
I'll tell you what has worked for me;
I have removed the rocker arm assy,and if there is an umbrella seal (or was at one time) I raise it or break it to allow the application of some deep-creep penetrating fluid. Then I leave it overnight.
The next day, I have injected air into the cylinder (piston at TDC compression, and anchored)and then tapped the valve stem a wee bit. You have to be careful to not drive the valve into the piston. If it was stuck, then after a few taps air pressure may drive the valve back up to the seat. If it does then I work the stem back and forth a few times. I listen to the sound that the valve makes when it returns to the seat. If it changes, as compression builds, then I know I'm getting somewhere.
If the valve sticks further and further down, I stop air-pressurizing, and move the piston down, to provide room. I dont bother going to coil-bind. If it doesn't come back with a few taps, it likely wont, and that spells tear-down time.
BTW, if you noticed a metalic noise during cranking, similar to a rod knock, but yet different; That's the sound a valve makes when it is slapped by a piston. Dont ask me how I know that,lol!
 
some times pulling a plug wire off and cranking it over will show you the cylinder with a problem ( it stops popping through) otherwise compression test would be next step like everyone else suggest .
 
I called around and got prices around 300 then 5-9 dollars for valves as needed. That's me bringing the heads to them of course. If I pull the heads will it be obvious what needs to be done? I have done my own automotive work in the past, swapped motors in an xj, transmissions in a suburban, intakes etc so am comfortable in doing the work just have never worked on heads, valves, pistons etc... Don't know why but it has always kinda intimidated me.
 
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