Jumped Timing Chain?

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70DusterBob

70DusterBob

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How do you know if the timing chain jumps? Do you have to retard it or do you have to advance the timing to get it to run right?
 
70DusterBob said:
How do you know if the timing chain jumps? Do you have to retard it or do you have to advance the timing to get it to run right?
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What makes you think it jumped a tooth?

Take driver side valve cover off and turn the engine over to 180 past TDC firing and look at the rockers on number 1 cylinder. If the are open the same its straight up. If the intake is open farther it's advanced. If the exhaust is open more it's retarded. The bigger the difference in valve opening the greater the advance or retard.
 
yellow rose said:
What makes you think it jumped a tooth?

Take driver side valve cover off and turn the engine over to 180 past TDC firing and look at the rockers on number 1 cylinder. If the are open the same its straight up. If the intake is open farther it's advanced. If the exhaust is open more it's retarded. The bigger the difference in valve opening the greater the advance or retard.
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I had to advance the timing by 5 degrees to get it to run the same at it used to, but it doesn't have the same power.
 
Who has actually seen a jumped chain on a Mopar? I never had as the chains are usually not that bad, but I did see a jumped chain on a Honda OHC but it has a hydraulic tensioner that went south, and the chain was long, the size of a 10 speeds. poll? that chain must have been thrashed or more likely the 'silent' plastic teeth wore out
 
pishta said:
Who has actually seen a jumped chain on a Mopar? I never had as the chains are usually not that bad, but I did see a jumped chain on a Honda OHC but it has a hydraulic tensioner that went south, and the chain was long, the size of a 10 speeds. poll? that chain must have been thrashed or more likely the 'silent' plastic teeth wore out
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Okay, if it stretches, which way would you have to adjust the timing to compensate for it?
 
I would almost suspect an ignition issue than jumped time, or maybe even a snapped off distributor roll pin before a jumped chain.
Have only seen a jumped chain on a stockish motor like twice in my life, even if the plastic broke off all the teeth of an old stocker.

If it really did jump you are never going to compensate for that with timing changes except maybe to get it to run (sorta) with way diminished performance.
 
You would have to advance it....................

If you have any idea of your (cam) valve timing, you can easily estimate where it's at by doing a "quick and dirty" degree right from the no1 valves. There's even a procedure in some year's service manuals
 
67Dart273 said:
You would have to advance it....................

If you have any idea of your (cam) valve timing, you can easily estimate where it's at by doing a "quick and dirty" degree right from the no1 valves. There's even a procedure in some year's service manuals
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That is what I was afraid of. I have been putting some "Serious" power through it and I think I stretched the chain, it is a stock chain, but I could be wrong of course. I will have to pull the valve cover, bring it to #1 and see where the valves are positioned. Thanks for answering.

I have a Chilton's for 1975, which is the year of the motor, it's a 360 BTW. I will re-post once I have found where the valves are positioned.
 
TrailBeast said:
I would almost suspect an ignition issue than jumped time, or maybe even a snapped off distributor roll pin before a jumped chain.
Have only seen a jumped chain on a stockish motor like twice in my life, even if the plastic broke off all the teeth of an old stocker.

If it really did jump you are never going to compensate for that with timing changes except maybe to get it to run (sorta) with way diminished performance.
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New distributor, same issue. I didn't know Mopar timing chains were that strong. Cool.
 
pishta said:
Who has actually seen a jumped chain on a Mopar? I never had as the chains are usually not that bad, but I did see a jumped chain on a Honda OHC but it has a hydraulic tensioner that went south, and the chain was long, the size of a 10 speeds. poll? that chain must have been thrashed or more likely the 'silent' plastic teeth wore out
Click to expand...
years ago, I was looking at my sister-in-law's 73 satellite 318, which she said was misfiring. While watching the rotor while cranking, it seemed to be jerking instead of rotating smoothly. So I grabbed the dampener and rotated it back and forth a little and there seemed to be some slack or delay in cam movement. I pulled the front off the engine, and there was only one tooth left on the cam gear! I could hardly believe it was still running. The plastic was gone from every single tooth, but one, and the remaining aluminum gear teeth were worn down to just shallow bumps. This was a bone stock application, so no crazy stresses on it, but no, I've never seen a mopar jump time.
 
I have seen plenty of small block mopars with trashed chains, the lowest mileage one was 84K in a truck my dad bought new, he said it just started running like crap, but made it home.
I picked up a nice 5th ave one time cheap off the original owner, non running, and the chain was broke.
 
On a motor with a trashed/worn chain...you can easily, sometimes by the belts, move the crank back and forth...the more back and forth it has till you feel it grab the gear, not good ..if you can do this, you'll easily be able to determine wether or not the chain and gear are done and it has indeed jumped. The cam gears are a nylon type to be silent and they're absolute garbage.
 
Way back in the day I delivered flowers for a local greenhouse. The delivery van was a 1968 Dodge and the timing chain did slip on it with only 192,000 miles on the engine. The boss was way impressed that I could diagnose and repair it. But then he traded it for a 1972 Ford Econoline :-(
 
Saw one jumed on a 360 in the 80's. Did get it to run 1/3 turn of the dizzy.barely ran.
 
MOST traditional V8s that "jumped time" were the ridiculous "plastic" timing sprockets used profusely in the 60's and 70's. Friend of mine replaced one when he changed cams in his low miles 70 Chev pu, 350. That sprocket had not yet jumped, and only had 30-35K miles, and MOST OF THE PLASTIC was GONE
 
Oh good GAWD yall stop wasting his time.

To the OP, run a compression test and post up the results. If the chain is jumped YOU'LL KNOW.
 
I appreciate everyone's replies. I have determined, just by reading the posts, that it probably hasn't jumped a tooth. Most likely it has stretched, but it is a little older, and I'm sure it has stretched without running any of the tests mentioned, it is not running with the power it had, and there is no reason on earth it would need 5 degrees more advance than it did for the previous 5 years it has been in the motor all the sudden. It does not ping under heavy acceleration in 3rd up a hill. It starts perfect when hot, and runs cool. I did put a new distributor in it, same deal, 5 degrees more advanced. I will first try the "back up the crank and see how long it takes to move the rotor in the distributor" test. Then I will run a compression test. If it fails that one, then I will be putting a much better chain in than stock. I'll go run those two tests now. They are free and easy.
 
Balancer ring slipped? Aparrently that happens.
Chains dont stretch. Pins and plates wear.
Hold a worn chain straight out with the pins vertical, beside the new one.
The plastic junk gears were designed to run quieter. Aka silent chain. Cant count the number of times i found chunks of tooth in pickup screens.
 
Well, I'm pretty sure it did stretch. It may not happen a lot, or often, but my crank shaft's pulley backed up about 13 degrees before it moved the rotor backwards, that was starting at TDC, going by the timing chain cover timing marks. The compression is down to 122 with 9.5:1 pistons. Something gave somewhere. Whenever I get a chance to get the timing chain cover off, I will post a pic with it on the car and if it has stretched, it should be just about touching in the middle if not touching at that much of a difference in those two measurements. If I remember right, which doesn't always happen, it is a dual sprocket chain, two sprockets in other words. It wasn't a plastic gear if I remember right. Not OEM, I thought it was stock, but then remembered I think it is a dual sprocket, or at least not plastic.

But thanks you guys for helping be "Certain" it is the timing chain "Before" I took it off... That is a lot of work.
 
70DusterBob said:
Well, I'm pretty sure it did stretch. It may not happen a lot, or often, but my crank shaft's pulley backed up about 13 degrees before it moved the rotor backwards, that was starting at TDC, going by the timing chain cover timing marks. The compression is down to 122 with 9.5:1 pistons. Something gave somewhere. Whenever I get a chance to get the timing chain cover off, I will post a pic with it on the car and if it has stretched, it should be just about touching in the middle if not touching at that much of a difference in those two measurements. If I remember right, which doesn't always happen, it is a dual sprocket chain, two sprockets in other words. It wasn't a plastic gear if I remember right. Not OEM, I thought it was stock, but then remembered I think it is a dual sprocket, or at least not plastic.

But thanks you guys for helping be "Certain" it is the timing chain "Before" I took it off... That is a lot of work.
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I'd be a little surprised if a double roller setup wore that much. I've reused them in engine builds, because they still looked good to me. If it does turn out to be worn that badly, I'd be interested in the brand so I could steer clear of it.
 
rustycowll69 said:
I'd be a little surprised if a double roller setup wore that much. I've reused them in engine builds, because they still looked good to me. If it does turn out to be worn that badly, I'd be interested in the brand so I could steer clear of it.
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So would I, but stranger things have happened. It's possible his chain is stretched that far.
 
I'm sure it has worn that much, but I'm not sure if it was a double or not. I can't remember. I will take a pic of it before I take it off.
 
It is a single sprocket all steel Car Quest Timing Chain. Made in USA. I haven't gotten it off yet, just found the box it was in in my shed. Ran the part number.
 
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