Jumped timing???

Jumped timing???

hopefulcj

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north florida
Vehicle(s)
1980 CJ7-258 I6, MC 2100 carb, team rush upgrade, T4, D300 tcase, D30 w/aussie locker in the front, AMC20 open, I think PO put 4.88s in the diffs, 35,000-135,000 miles, you pick. 4"susp lift, 2" shackle, 35" A BAD WORD cepek AT's on black steel wheels, 1 1/4" spydertrak wheel spacers, most everything else i believe is stock, finding things out as I go
About a month ago I bent the 6th cylinder rod guide/bridge. Before finding this, my mechanic thought I might have an intake valve not seating, and this might have thrown off the timing. Now that is all fixed, and the jeep was running fine. I recently put on a MC 2100. I set the timing to 8*BTDC with a light, and the jeep ran like :dung:. This scared me. I remembered about the timing chain issue before so I set the timing by ear like the mechanic did, I got the jeep running pretty good, though it still lacks some power and lags if I really get on it. Their is no pinging or anything. The notch on the wheel points straight up (12 o'clock) with the current timing. It should be pointing more at 2'ocllock to even be read on the TDC scale.
This leads me to think that the timing chain jumped, since I can get the engine running, but the timing is not set where its supposed to be.

-Engine has probably been rebuilt, engine is all orange including some of the lower end gaskets.
-Mechanic replaced all upper gaskets.

I am going to try to set the timing by vacuum gauge.. warm up to operating tem, plug into manifold vac., plug advanced vac nipple, turn dizzy to get the best pressure, then turn back 1 hg.

Should I go ahead and replace the timing chain and gears? The mechanic was going to do this but decided not to since we didnt have to machine the head? Will I damage the engine internals ig I keep driving it like it is? I have read that it will on some of the searches I have done, and I have also heard that this is normale with old engines and to just time it by ear since its an older engine, and the factory timing specs arn't accurate anymore.

Thanks, thanks, and thanks again. Im getting long winded like my dad.
Jacob.
 
Last edited:
IMHO if you think you have issues with the timing chain and your mechanic was going to change it, I think I would be looking in to changing it. Or the very least check and see if it is timed right and did not jump a tooth, or the chain and sprockets aren't chewed up. Or to much slack in the chain.
 
You can roughly check your timming chain by pulling the dist. cap off and turning the crank with the aid of your timming marks, turn one direction till 0 degrees then go the other way watching for movement in the rotor and when it starts to move see were you are on your timing marks at the harmonic balancer. This is not totaly acurate because of dist gear wear but will give you an idea, you can pull the dist. and watch the gear drive/cam for more acuracy. From what I've seen posted up to 10 degrees is concidered OK but beyond is R & R time. when I checked my 78K miles motor it had 5 degrees of lag.
 
I would do the chain and gears. Fresh paint on the outside does't mean it's OK on the inside.
 
Ill check the slack in the chain by doing what Sasquatch says. I plan on replacing the timing chain and gears in about a monthe when my father comes down. However we have never changed out a timing chain.

So, once we remove the chain and geats, how do we re-align the gears/chain back to TDC so that I can actually use the 0TDC scale on the flywheel? (not sure if thats what it is, but it sounds right) Do I rotate the engine until I get pressure from the 1st spark plug hole? After finding TDC do I need to rotate the dizzy so that the rotor is pointing at 1? I will prob end up asking the mechanic to come help out once we remove the radiator, fan, and anything else in the way.

Thanks for your replys. BTW I timed it last night witha vacuum gauge, no more lag, and lots of power. This makes me feel better.
 
You can roughly check your timming chain by pulling the dist. cap off and turning the crank with the aid of your timming marks, turn one direction till 0 degrees then go the other way watching for movement in the rotor and when it starts to move see were you are on your timing marks at the harmonic balancer. This is not totaly acurate because of dist gear wear but will give you an idea, you can pull the dist. and watch the gear drive/cam for more acuracy. From what I've seen posted up to 10 degrees is concidered OK but beyond is R & R time. when I checked my 78K miles motor it had 5 degrees of lag.


I would do what Sasquach suggested to see how much slack and where you have.

Suggest start by finding TDC on #1 compression stroke. Take all your spark plugs and look at them, they should be tan, if dark or sooty or oilly write down condition for each one. This makes engine much easier to turn over. Use the balancer nut turn engine in operational direction till you feel compression on #, can look in fill hole of valve cover to verify compression stroke with the valve movememt. Use a chopstick to find the top of stroke. Balancer should be at 0 time mark and rotar should be pointing to the #1 position.

Balancer can spin, chain jump, HEI could have been eating you cam gear, it could be a few things ..... so best to start at TDC and the look at the slack in time chain.

Cannot tune a engine by .........ear.......... get a time light... simple ones can be had for 25 and Fleet Farm in my area has the Digital with advance idication for $75. I cannot time by ear so I would also assume you cannot do it.


Then you KNOW exactly where you are. Mark the balancer with a sharpe and you have a visual where your time via balancer is.. Runs ok great... then runs poor ck the time light
 
I had to time it by ear just to get it to run. It wont run unpredictable the timing notch is pointing straight up, I checked this with a timing light. This is why I had to do it by ear and vacuum gauge. its in the original post.
 
I understand that.....

Your balancer could have spun, dist gear issue, time chain loose and jumped. Could be just one, some or all threee...

Still suggest you do TDC, Verify balancer, then mark, and changes you will see and know... Even if you have to put a "new white time mark" on the balancer... The idea is to get a base line and then watch your changes..

Do you have a HEI distributor from the internet????
 
258's are easy to change the timing gears and chain.

The marks are just as easy.

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MN CJ7, and don't have Hei dizzy, just the team rush upgrade.

73 cj, so in the process of rotating the engine to align the timing marks, this will take care aligning everythingelse? If that's the case then this does seem like an easy job. (knock on wood)
 

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