broken timing chain

donald

could a broken timing chain cause my motor not to turn over? Brand new battery and it acts like there is no power to turn it over like way to much compression.

jeepsr4ever

Was it a recent rebuild? It will barely turn something mechanical is holding it up. Whats the history on it?

tufcj

Only if the chain jammed inside the cover, and chances are that the cover would break. Put a large socket on the crank bolt and try to turn it backwards. I've only seen a timing chain break once in my life, and that was on a small block chevy. Without knowing the history of the motor, it's hard to say what's wrong. I'd pull the spark plugs and try to turn it over, could be water or fuel has a cylinder hydro-locked. Could be a dropped valve, could be rust from sitting, could be a seized piston or seized rod or main bearing. Just too many possibilities. Bob tufcj

donald

motor was not rebuilt any time within the past yyear or so since i have had it. The thing is if I pull start it the jeep will fire up but wont stay running if i dont flutter the gas. What if it jumped time will it cause the thing to act like its seized up?

tufcj

If the chain was broken, it wouldn't run at all. The distributor is driven from the cam, which wouldn't move it the chain was broken. It could have jumped time. Late 70's, early 80's motors were built with nylon teeth on the cam gears (for noise and cost savings). They would break down over time and it could jump time. They usually lasted around 80K miles. Has the starter been replaced? I've seen the bushings at the ends of the starter wear oval, then the armature drags against the case of the starter. It spins, but the drag slows it considerably. All cables and connections been checked and cleaned? Bob tufcj

msalaba

tufcj wrote
Late 70's, early 80's motors were built with nylon teeth on the cam gears (for noise and cost savings). They would break down over time and it could jump time. They usually lasted around 80K miles.

Bob
tufcj

Really? I replaced the timing chain set on my 78 360 last year and had factory cast gears. Same with the 85 I'm in the process of rebuilding. I thought the nylon gears were a Chevy thing. If they did come factory w/ nylon gears it would be a good indication that someone was in there before me!

#-o

msalaba

donald wrote
could a broken timing chain cause my motor not to turn over? Brand new battery and it acts like there is no power to turn it over like way to much compression.

donald wrote
motor was not rebuilt any time within the past yyear or so since i have had it. The thing is if I pull start it the jeep will fire up but wont stay running if i dont flutter the gas. What if it jumped time will it cause the thing to act like its seized up?

What Engine? IIRC, most AMC engines use Motorcraft starters. They get weak with age like anything else.

Sounds like you have a bad starter combined with other gremlins that are giving you fits. #-o

I would start with some basic maintanence like check :idea: the plugs, compression, ign. timing and carb. Even something as simple as a plugged fuel filter will give you some serious problems.

More info could go a long way to a more accurate diagnosis.

:-|

tufcj

I bought my 77 CJ with 8000 miles on it. It jumped time at about 90K, the 304 had a nylon cam gear in it. Maybe it was just the 304s? I know they did use the nylon tooth gears in some engines. Bob tufcj

tarior

I had a '73 Matador with a 360 that came with a nylon timing set.

Henry Lavrenz

Yes - a broken timing chain can cause a AMC engine not to turn over, a AMC engine (like a old mopar) is not free wheeling. Meaning a valve can hit a piston if the valve timing is way off. If a AMC jumps time - 99% of the time you a hosed big time. The force required to turn a camshaft is tremendous, and if the teeth are at the point of failing - the chain would not jump just one tooth. A timing chain jumping one tooth and stopping there and the engine running for any length of time there after is about the most unbelieveble thing that I'v ever heard. Hankrod oops' that is a bit harsh, sorry just me. Hankrod

tufcj

With an AMC V-8 engine, it's going to depend on compression and cam lift. My bone stock 304 slipped by one tooth, and I was able to get it home (although running poorly) by twisting the distributor, resetting the timing. Once home and shut off, it skipped several more teeth when I tried to restart it again. There was never any valve to piston contact or bent valves or pushrods. I dropped a new timing set in it and happily drove another 30K miles before swapping in a 360. I did have a Mopar with a 383 Magnum engine (prior to the Jeep) that had a nylon gear, when that jumped, it bent nearly every pushrod in it, and I had to have the heads done because of bent valves. But it was a higher compression, higher lift cam engine. Bob tufcj

crazydog

The 360 that was in my 1979 Cherokee had a nylon gear when I got after about a year and with an unknown number of miles the gear disintegrated. After I put in a new timing set, I really regretted not swapping in a cam at that time. But, building the 401, got me over that real quick.